Velleman K40x0, the very model of an all-round amp
Andre Jute
> "Andre Jute" <fiul...@yahoo.com> wrote
>
> > Real tubies build real valve amp kits, like
> > my Velleman K4000, three EL34 per side for 18W in Class A and 101W in
> > Class B (measured, they claim only 16/96W). Now that is an amp that
> > leaves hairy footprints.
>
> Interesting you should mention the Velleman. It is indeed a good sounding
> amp. It is a long time since I have seen a K4000, but I seem to recollect
> it had four EL34's in push pull parallel per side.
PPP.
> It seems as though the K4000 is discontinued.
Mine is ancient. Early to mid-1990s, at a guess, without looking up
the reviews I wrote of it.
> I listened to a 4040 not too long ago, with a pair of splendid Tannoy
> Canterbury
> SE speakers. Very pleasing indeed. The amp was running far below its full
> power potential.
Quite a bizarre thing to say, I suppose, but the Velleman is probably
overmatched to the Tannoys. It has around 16 to 18W in Class A alone.
I sometimes used mine for driving a bass bin, where its 100W in Class
A/B could sometimes come into play, at least theoretically (I'm not a
headbanger).
>The noise floor was exceptionally low. Later, a quick
> look on the bench revealed the noise floor to be 100µV, so a
> SNR of 105dB and at 96W, the THD was only 0.1%
It depends on your outlook whether you view the Velleman K40x0 as that
rare thing, a perfect all-round amp -- or as a perfectly schizophrenic
amp: on the one hand superbly well designed and good-sounding,
escpecially in that very hefty Class A segment, a delicate match to
ESL-63, on the other hand a brutish bass thumper on demand. As an all-
round amp of excellent quality and durability it is of course a very
great bargain at the price.
> The Belgians know how to make more than just chocolates:-)
We used to make a round trip of 50 miles to buy Belgian chocolates in
Cork...
> Regards
> Iain
Andre Jute
Visit Jute on Amps at http://members.lycos.co.uk/fiultra/
"wonderfully well written and reasoned information
for the tube audio constructor"
John Broskie TubeCAD & GlassWare
"an unbelievably comprehensive web site
containing vital gems of wisdom"
Stuart Perry Hi-Fi News & Record Review
Bret Ludwig
> On Oct 19, 12:11 am, "Iain Churches" <Iai...@kolumbus.fi> wrote:
>
> > "Andre Jute" <fiul...@yahoo.com> wrote
>
> > > Real tubies build real valve amp kits, like
> > > my Velleman K4000, three EL34 per side for 18W in Class A and 101W in
> > > Class B (measured, they claim only 16/96W). Now that is an amp that
> > > leaves hairy footprints.
>
This was the all-on-a PCB, toroidal output transformer kit offered
for well in four figures through OCSL at around that time. I thought
it was a stinky deal then and worse now. Toroid outputs and PCB
mounted power tubes are just not a good idea.
Multi-grid
> overmatched to the Tannoys. It has around 16 to 18W in Class A alone.
> I sometimes used mine for driving a bass bin, where its 100W in Class
> A/B could sometimes come into play, at least theoretically (I'm not a
> headbanger).
>
hey-Hey!!!,
An amp with maximum output happening with one phase of its PP set cut
off is *NOT* class A. A real class A amp has both phases conducting at
maximum power, and not from some variable pitch grid winding, remote
cut-off stuff either.
That Vellman amp is an AB, and barely so at that.
cheers,
Douglas
John Byrns
Multi-grid <pen...@netscape.com> wrote:
> hey-Hey!!!,
> An amp with maximum output happening with one phase of its PP set cut
> off is *NOT* class A. A real class A amp has both phases conducting at
> maximum power, and not from some variable pitch grid winding, remote
> cut-off stuff either.
Is there actually a power tube with a variable pitch grid winding
designed to do this? I never heard about it before, inquiring minds
want to know more.
Regards,
John Byrns
--
Surf my web pages at, http://fmamradios.com/
Andre Jute
What are you on about, Dougles? I just told you, it is a class AB amp.
Class AB amps by definition have some class A output and the rest in
Class B. If you want an unadulterated Class A amp with a 100W output,
you're going to be paying real money, and if you're a snob who wants
it in SE, you're going to be paying Range Rover Vogue money. I know; I
built an 80W SE amp, which of course by definition ran only in Class
A. The Velleman is relatively inexpensive, very sturdy, very good
value amplifier kit from the most famous makers of all kinds of
electronic kits in the world. But its price will look a tip to a
doorman by the time you finish paying for a 100W Class A amp.
And what's that rubbish about "maximum output" anyway? By definition a
class AB amp's Class A output is at some lower power than maximum,
otherwise it would be a Class A amp, period. The whole point about a
Class AB amp is that most music is played where such an amp makes its
sweetest sounds, but that it has headroom for any contingency, though
you sacrifice a little something in quality when that headroom is
taken up.
If your taste is so refined that you must have nothing but Class A,
there are a bunch of designs for Class A amps on my netsite. And, for
the sake of completeness, my own favourite everyday amp is my own T113
"Triple Threat" design, which runs PP EL34s in triode and strictly in
Class A. But you'd need about 8 of those to get 100W...
You know an audiophool snob when he starts talking about "pure" Class
A...
Multi-grid
> On Oct 19, 3:50 pm, Multi-grid <pent...@netscape.com> wrote:
>
> > > overmatched to the Tannoys. It has around 16 to 18W in Class A alone.
> > > I sometimes used mine for driving a bass bin, where its 100W in Class
> > > A/B could sometimes come into play, at least theoretically (I'm not a
> > > headbanger).
>
> > hey-Hey!!!,
> > An amp with maximum output happening with one phase of its PP set cut
> > off is *NOT* class A. A real class A amp has both phases conducting at
> > maximum power, and not from some variable pitch grid winding, remote
> > cut-off stuff either.
>
> > That Vellman amp is an AB, and barely so at that.
> > cheers,
> > Douglas
>
> What are you on about, Dougles? I just told you, it is a class AB amp.
> Class AB amps by definition have some class A output and the rest in
> Class B.
No it doesn't, it has no power in Class A. That's why it is called an
AB amp. It is really simple.
If you want an unadulterated Class A amp with a 100W output,
> you're going to be paying real money, and if you're a snob who wants
> it in SE, you're going to be paying Range Rover Vogue money. I know; I
> built an 80W SE amp, which of course by definition ran only in Class
> A. The Velleman is relatively inexpensive, very sturdy, very good
> value amplifier kit from the most famous makers of all kinds of
> electronic kits in the world. But its price will look a tip to a
> doorman by the time you finish paying for a 100W Class A amp.
I don't recall ever telling you what I wanted, or owned, or for that
matter what I've built. None of that has any bearing on your marketing-
based dafynishion of what you'd like an AB amp to be.
>
> And what's that rubbish about "maximum output" anyway? By definition a
> class AB amp's Class A output is at some lower power than maximum,
> otherwise it would be a Class A amp, period.
Just because both of the finals are conducting does not mean it is
Class A. That is reserved for amps that keep both conducting *AT FULL
POWER*. Why bastardize the definition just because some marketing fool
likes says it's OK? A Class AB amp doesn't have any Class A output.
Both phases conducting does not make Class A....or is that too hard to
grasp?
The whole point about a
> Class AB amp is that most music is played where such an amp makes its
> sweetest sounds, but that it has headroom for any contingency, though
> you sacrifice a little something in quality when that headroom is
> taken up.
>
> If your taste is so refined that you must have nothing but Class A,
> there are a bunch of designs for Class A amps on my netsite.
I don't think I'll be considering any of those amps. Kinda off-the-
rack and boring.
And, for
> the sake of completeness, my own favourite everyday amp is my own T113
> "Triple Threat" design, which runs PP EL34s in triode and strictly in
> Class A. But you'd need about 8 of those to get 100W...
>
You know an audiophool snob when he starts talking about "pure" Class
> A...
>
Probably just somebody who knows how to use the language properly. You
can join the club anytime you wish to conduct yourself properly....and
leave it just as quickly.
cheers,
Douglas
Multi-grid
> In article <1192834206.499080.17...@i13g2000prf.googlegroups.com>,
>
> Multi-grid <pent...@netscape.com> wrote:
> > hey-Hey!!!,
> > An amp with maximum output happening with one phase of its PP set cut
> > off is *NOT* class A. A real class A amp has both phases conducting at
> > maximum power, and not from some variable pitch grid winding, remote
> > cut-off stuff either.
>
> Is there actually a power tube with a variable pitch grid winding
> designed to do this? I never heard about it before, inquiring minds
> want to know more.
>
> Regards,
>
> John Byrns
>
> --
> Surf my web pages at, http://fmamradios.com/
Hi John,
I don't know of any either, but given the definition of Class A, I
thought it wise to rule out the remote cut-off behaviour that *COULD*
provide a loophole to somebody fixed on disagreement, yes?
cheers,
Douglas
sparky
> "wonderfully well written and reasoned information
> for the tube audio constructor"
> John Broskie TubeCAD & GlassWare
> "an unbelievably comprehensive web site
> containing vital gems of wisdom"
> Stuart Perry Hi-Fi News & Record Review
Of all the decent amps out there why would you pick something like
This?
Andre Jute
Yes, I see what this is about: another clown storming into RAT with a
mission to see me off. Thanks for coming, Dougles, but I don't think I
would care to belong to any club that lets you in.
> cheers,
> Douglas
Multi-grid
>
> - Show quoted text -- Hide quoted text -
>
> - Show quoted text -
hey-Hey!!!,
Well Andre, you can imagine my mission to be what ever it you want.
Again, that has no bearing what so ever on your mis-use of the
definition. Please stay on topic if you'd be so kind. Quit clouding
the issue please.
Do people go 'storming into RAT with a mission to see me off' alot
lately? Are you paranoid or something? Where would you get such an
idea?
I'll type slowly so you can understand it, this club I referred to
only requires its members to use accepted audio definitions and terms
properly. Of course it doesn't really exist, save for in
metaphore...but an accomplished writer like you would know all this,
right?
While you're at it, a schematic of your 80W SE amp would be nice to
look at.
cheers,
Douglas
Iain Churches
"Andre Jute" <fiu...@yahoo.com> wrote in message
news:1192793240.0...@v29g2000prd.googlegroups.com...
On Oct 19, 12:11 am, "Iain Churches" <Iai...@kolumbus.fi> wrote:
>The noise floor was exceptionally low. Later, a quick
> look on the bench revealed the noise floor to be 100ÁV, so a
> SNR of 105dB and at 96W, the THD was only 0.1%
It depends on your outlook whether you view the Velleman K40x0 as that
rare thing, a perfect all-round amp --
(snip)
Oh,. I don't think it is anywhere near that!
I regard it as a good-sounding DIY project, no more.
The fact that the tube sockets are mounted on the PCB
really put me off.
I have a Radford STA 100. So no contest.
Iain
Jon Yaeger
>
> (snip)
>
> Oh,. I don't think it is anywhere near that!
> I regard it as a good-sounding DIY project, no more.
> The fact that the tube sockets are mounted on the PCB
> really put me off.
>
> I have a Radford STA 100. So no contest.
>
> Iain
>
I owned one that another fellow put together. I remember replacing some of
the 10 ohm resistors because of excessive cathode current draw.
It was a nice looking amp, with plenty of power. The PCBs were a turn-off,
but not a killer for me (Hey, if you want to have some REAL fun, do
component-level work on an Audio Research D-70. What a nightmare to repair!)
In my continuing search for the holy grail of sound, that amp went to a new
owner. To my ears, the sound was kind of harsh for a tube amp, and lacking
excitement.
I agree that it is "a good-sounding DIY project."
Jon
Iain Churches
"Jon Yaeger" <jon...@bellsouth.net> wrote in message
news:C340E7AF.A0344%jon...@bellsouth.net...
>
> I owned one that another fellow put together. I remember replacing some
> of
> the 10 ohm resistors because of excessive cathode current draw.
>
> It was a nice looking amp, with plenty of power. The PCBs were a turn-off,
> but not a killer for me (Hey, if you want to have some REAL fun, do
> component-level work on an Audio Research D-70. What a nightmare to
> repair!)
>
> In my continuing search for the holy grail of sound, that amp went to a
> new
> owner. To my ears, the sound was kind of harsh for a tube amp, and
> lacking
> excitement.
>
> I agree that it is "a good-sounding DIY project."
>
of interest in tube audio, then it has served a very useful purpose.
Iain
Andre Jute
> "Andre Jute" <fiul...@yahoo.com> wrote in message
>
> news:1192793240.0...@v29g2000prd.googlegroups.com...
> On Oct 19, 12:11 am, "Iain Churches" <Iai...@kolumbus.fi> wrote:
>
> >The noise floor was exceptionally low. Later, a quick
> > SNR of 105dB and at 96W, the THD was only 0.1%
>
> It depends on your outlook whether you view the Velleman K40x0 as that
> rare thing, a perfect all-round amp --
It's all opinion. Some opinions are informed by relevant experience
and therefore more valuable. Some opinions are informed by nothing but
street corner gossip or personal animosity and are therefore
worthless.
> Oh,. I don't think it is anywhere near that!
> I regard it as a good-sounding DIY project, no more.
> The fact that the tube sockets are mounted on the PCB
> really put me off.
>
> I have a Radford STA 100. So no contest.
And I have a Quad II. No contest, to my mind at least; it depends what
you want to measure and hear. Except that the Quad II doesn't put out
100W. Let's compare apples with apples, not with gilded plums, mmm?
I could compare the Velleman K4000 100W with a bunch of other kits I
have built and used extensively: Arion Adonis PP 5581 20W, Audio
Innovations Classic Stereo 25 PP EL34 25W, Triode Supply Japan Miyabe
300B SEPP 16W, etc, etc, and in no instance would it be comparing
apples with apples, for the good and simple reason that none of them
have 100W. In that the Velleman K40*0 stands alone, and gives the
beginner versatility to use the most grossly insensitive bookshelf
speakers to get real oomph on any music whatsoever. I could have
chosen any of the amps listed, or any of the other kits I have built,
including some I don't list because they have less than 10W, and said
they're fine on some aspect (or even the best) but, while all of them
have served me very well indeed, none of them can be put up against
the Velleman without admitting some handicap in some perfectly common
everyday use for an identifiable group of users.
I might add that my favourite among that lot is the AI, which is a
gentleman's amp, never intrusive; an amp you can play 14 hours every
day and never find fault with. I find the Velleman far too analytical
for my taste but that is because it is so accurate, a characteristic
many value. But, to illustrate once more that all this is relative to
usage and opinion, I play mainly chamber music at low volume;
symphonic or other "big" music played on insensitive speakers
*requires* a big amp. If I were into heavy metal or whatever the
current fave of the loud set is called, I wouldn't touch any of my
favourite amps for chamber music -- they'd all be less than convincing
-- I'd go straight to the Velleman and acoustic overload heaven.
By the way, the Velleman K40*0 is eminently tweakable. On my old
netsite I had an entire big section devoted to altering the factory
spec to make it sound like anything you wanted it to sound like. The
"harshness" Jon Yaeger objects to, for instance, was just a matter of
swapping out a ceramic (! now that's an excess of engineering...) cap
for a film cap; you would of course sacrifice a little of the
excellent noise spec (which was why the designer put it in there) but
might consider the loss worthwhile to gain precisely the sound you
want. I'm amazed that Yaeger doesn't know that.
As for the snobbery of demanding point to point wiring on kits, go
right ahead: you'll be helping to kill the hobby off faster than is
necessary. In my experience eliminating the PCB, or insisting on
sockets mounted to the chassis, just about triples the price of the
kit, and ensures that the successful assembly rate is halved.
(Suppliers who give a completion guarantee, or who provide a
handholding service, keep very good records of these matters! Or you
can read between the lines in the instructions and on the sites of
those who sell PTP kits how fed up they are with seeing time and
profits dribble away in support to eejits who cannot follow simple
instructions.)
If you insist on hardwiring, nothing stops you buying a Velleman K40*0
kit, or any other kit with a chassis, to get the design and all the
parts, and simply drilling the cover to hold sockets for the tubes and
then fitting the components to tag strips you supply. Nor is there any
secret to designing a PCB construction properly for heat management:
either ascertain that the kit has ceramic standoffs for power tubes
and resistors as standard, or add them yourself. I'm really amazed at
discovering DIYers who brag about their craftsmanship, then complain
about an amp because it is designed to be built on a PCB: if you don't
like it, change it!
> Iain
For those who need or want a 100W and prefer tubes, the Velleman K40x0
is unique, zero competition that I know about.
I don't see much point in nitpicking commercial amps against
irrelevant self-proclaimed "standards"; the test is whether the thing
works in the hands of owners, and the K40*0 worked fine for a decade
and more in my hands. We've already had a bunch of clowns in this
thread condemning one of the most succesful commercial amps in the
world *without ever seeing one or hearing it*. That sort of street
corner gossip repeated as gospel is what trashes the reputation of
RAT, not putting down the thieves of intellectual rights or netbullies
and netstalkers -- on the contrary, it is toleration and protection of
such people that trashes our reputation.
Phread
"Andre Jute" <fiu...@yahoo.com> wrote in message news:1193062450.9...@v23g2000prn.googlegroups.com...
> On Oct 21, 7:48 am, "Iain Churches" <Iai...@kolumbus.fi> wrote:
> > "Andre Jute" <fiul...@yahoo.com> wrote in message
> >
> > news:1192793240.0...@v29g2000prd.googlegroups.com...
> > On Oct 19, 12:11 am, "Iain Churches" <Iai...@kolumbus.fi> wrote:
> >
> > >The noise floor was exceptionally low. Later, a quick
Horseshit, Andre. It isn't the reputation of RAT that's trashed, it's the
atmosphere that people have been fleeing. That atmosphere has been
trashed by your relentless personal attacks on everyone you can find
even the slightest reason to go after.
But it's OK; pretty soon you and your sock puppets will have this place
all to yourselves. You'll be able to launch devastating attacks on your
sock puppets every day and no one will complain unless you do it for
them.
He he, Andre, what a horse's ass you are.
Multi-grid
>
> I don't see much point in nitpicking commercial amps against
> irrelevant self-proclaimed "standards"; the test is whether the thing
> works in the hands of owners, and the K40*0 worked fine for a decade
> and more in my hands. We've already had a bunch of clowns in this
> thread condemning one of the most succesful commercial amps in the
> world *without ever seeing one or hearing it*. That sort of street
> corner gossip repeated as gospel is what trashes the reputation of
> RAT, not putting down the thieves of intellectual rights or netbullies
> and netstalkers -- on the contrary, it is toleration and protection of
> such people that trashes our reputation.
>
> Andre Jute
>
I'll second Phread, it is the personal attacking that makes this place
less-than. If you'd examine the history, RAT was a reasonable going
concern until the Jute v. Magnetquest war. Seems Andre was unable to
make a legitimate criticism of Mikey stick.
So then Andre, you mention an AB amp having A power, you reference an
80W SE amp, claim an off the rack Vellman kit is brilliant, and then
attack anybody who'd have the guts to say you've over reached. Even
with poor S/N ratio there is still signal. Let's see some from you.
cheers,
Douglas
mick
<snip>
>
> So then Andre, you mention an AB amp having A power, you reference an
> 80W SE amp, claim an off the rack Vellman kit is brilliant, and then
> attack anybody who'd have the guts to say you've over reached. Even with
> poor S/N ratio there is still signal. Let's see some from you. cheers,
Surely though, a class AB amp such as the Vellman *is* running in class A
up to the point where one output device starts to turn off isn't it? The
changeover to class B happens at that point and is dependent on the
quiescent current in the outputs.
A true class A amp is only a special case of the normal AB class. It's
just that it clips symmetrically instead of moving smoothly into class
B. ;-)
--
Mick (Working in a M$-free zone!)
Web: http://www.nascom.info http://mixpix.batcave.net
Multi-grid
> Surely though, a class AB amp such as the Vellman *is* running in class A
> up to the point where one output device starts to turn off isn't it? >
Nope, not a chance. That both tubes are conducting does not mean it is
A. Have some respect...:) AB amps don't have any A power, that is why
there is a seperate classification.
cheers,
Douglas
Andre Jute
> On Mon, 22 Oct 2007 13:50:47 -0700, Multi-grid wrote:
>
> <snip>
>
> > So then Andre, you mention an AB amp having A power, you reference an
> > 80W SE amp, claim an off the rack Vellman kit is brilliant, and then
> > attack anybody who'd have the guts to say you've over reached. Even with
> > poor S/N ratio there is still signal. Let's see some from you. cheers,
Who is this fellow "Multi-grid", and why is he addressing me?
> Surely though, a class AB amp such as the Vellman *is* running in class A
> up to the point where one output device starts to turn off isn't it? The
> changeover to class B happens at that point and is dependent on the
> quiescent current in the outputs.
I would have thought anyone with a handle like "Multi-grid" would have
taken that sort of basic tube knowledge from the teat. Mind you, I
remember when Ron Bales wanted us here on RAT to give everyone who
claimed a "tubie-handle" a test of tube knowledge to ensure they don't
give a respectable hobby a bad name by wielding their ignorance like
clubs. That was about 1998. Looks like this "Multi-grid" fellow is a
prime candidate for the Bales Test.
> A true class A amp is only a special case of the normal AB class. It's
> just that it clips symmetrically instead of moving smoothly into class
> B. ;-)
It is beneath my dignity to rise to such provocation -- sniff. A Class
AB amp is a compromised Class A amp, and it probably requires negative
feedback too to work even acceptably. A properly designed Class A amp
never clips because the operating parameters were so chosen that it
runs out of signal from the intended source before it can clip (that
is one reason why the design instructions on my netsite feature the
*design center* process so heavily). It is only "engineers" who
"design" amps to hog the maximum power from each tube who even need a
concept like clipping; for sane tubies it is obsolete terminology.
> --
> Mick (Working in a M$-free zone!)
> Web:http://www.nascom.infohttp://mixpix.batcave.net
Andre Jute
Our legislators managed to criminalize fox-hunting and smoking; when
will they get off their collective fat backside and criminalize
negative feedback? It is clearly consumed only by thickoes.
Multi-grid
> never clips because the operating parameters were so chosen that it
> runs out of signal from the intended source before it can clip (that
> is one reason why the design instructions on my netsite feature the
> *design center* process so heavily).
Stay on topic please.
While you're at it, please refrain from making personal attacks, it is
beneath you( I hope ).
Class A has nothing to do with its input signal. The finals clip
symetrically. Or perhaps unsymetrically if it is power limited A, so
to say overbiased given the load and B+. If you have plate dissipation
to spare, it is certainly possible. Matter of fact I am listening to
one such amp now...:)
cheers,
Douglas
maxhifi
Multi-grid wrote:
I believe the point it changes from 'class A' to 'class AB' is commonly
accepted to be the point where the output stage begins to draw more
current from the power supply. By commonly accepted, I mean I've read a
ton of magazine reviews of tube amps where they use this logic, stated
almost exactly as Andre has used it.
In other words, the amp is biased a bit hotter than class B, and this
lowers low level distortion a bit at the expense of peak power output.
Stating that "the amplifier is Class A until XXX watts", really, is
telling you how hot the tubes are biased relative to the two extremes of
pure class A (full dissapation), and pure class (cut off).
John Byrns
Andre Jute <fiu...@yahoo.com> wrote:
> On Oct 22, 2:33 pm, mick <not.h...@invalid.invalid> wrote:
> > On Mon, 22 Oct 2007 13:50:47 -0700, Multi-grid wrote:
> >
> > <snip>
> >
> > > So then Andre, you mention an AB amp having A power, you reference an
> > > 80W SE amp, claim an off the rack Vellman kit is brilliant, and then
> > > attack anybody who'd have the guts to say you've over reached. Even with
> > > poor S/N ratio there is still signal. Let's see some from you. cheers,
>
> Who is this fellow "Multi-grid", and why is he addressing me?
Hi Andre,
This fellow "Multi-grid" is either a Troll, ignorant, or most likely
both, his goal appears to be trying to stir up trouble so he is best
ignored.
Multi-grid
>
> - Show quoted text -
Class A has nothing to do with dissipation either. Just because some
marketing group noticed that class A means something good, does not
make it right either. Just because it seems to make sense is no reason
to bastardize the definition. Find some other way to describe it.
cheers,
Douglas
Multi-grid
> In article <1193094635.545992.56...@i13g2000prf.googlegroups.com>,
It appears you folks are living up to your reputation for making
personal attacks. It isn't this:
That sort of street
corner gossip repeated as gospel is what trashes the reputation of
RAT, not putting down the thieves of intellectual rights or
netbullies
and netstalkers -- on the contrary, it is toleration and protection
of
such people that trashes our reputation.
that's doing RAT harm. Getting nasty on the other hand...
cheers,
Douglas
Peter Wieck
> This fellow "Multi-grid" is either a Troll, ignorant, or most likely
> both, his goal appears to be trying to stir up trouble so he is best
> ignored.
Ever ready with the diaper, John?
Peter Wieck
Wyncote, PA
Eeyore
Multi-grid wrote:
> maxhifi <n...@spam.com> wrote:
>
> > Stating that "the amplifier is Class A until XXX watts", really, is
> > telling you how hot the tubes are biased relative to the two extremes of
> > pure class A (full dissapation), and pure class (cut off).- Hide quoted text -
>
>
> Class A has nothing to do with dissipation either. Just because some
> marketing group noticed that class A means something good, does not
> make it right either. Just because it seems to make sense is no reason
> to bastardize the definition. Find some other way to describe it.
The definition of Class A is very simple. It requires that the output device(s)
never cease conducting under any signal condition.
Graham
mick
Correct. A class AB amp fulfills this up to the point where one side
starts to turn off.
Andre Jute
> > Multi-grid wrote:
> >> Class A has nothing to do with dissipation either.
Then Poopie wrote:
> > The definition of Class A is very simple. It requires that the output
> > device(s) never cease conducting under any signal condition.
Then Mick http://www.nascom.info and http://mixpix.batcave.net wrote:
> Correct. A class AB amp fulfills this up to the point where one side
> starts to turn off.
I can see what you're getting at, Poopie, and so can Mick apparently,
but I don't think I want to wear your definition where it says "under
any signal condition". That's most misleading, especially with a
newbie on the board who stubbornly keeps claiming signal has nothing
to do with Class A. Any power stage that is hitherto Class A can
driven to cutoff by simply increasing the signal until the output cuts
out at either zero current or zero voltage.
In any and all cases, Class A is defined, though usually implicitly
rather than explcitly, as at a particular, *limited* signal voltage. I
therefore prefer the definition of Class A which says simply:
***Class A operating conditions do not permit the output device to
cease conducting.***
If you insist on describing the signal condition, you could add the
words *at the design or intended or specified signal*.
As for Dougles Multi-grid's silly insistence that signal and
dissipation have nothing to do with Class A operation, thanks for the
giggle, sonny, but you'd better hit the books lots more before you
seek entry to this club. In particular, you should pay attention to
this, which often comes as a bolt from the blue to repair hacks like
you, who tend to assume that the parameters are godgiven and fixed:
the *designer* chooses the plate voltage and negative bias, that sets
the current at quiescence, through which the designer then runs the
loadline at a particular angle when he chooses a primary impedance for
his output transformer, the slope of the loadline determining how far
the quiescent point is from current cutoff (or voltage cutoff...), and
that in turn defines the signal voltage that can be put in for Class A
operation, which in turn defines the output power. Thus the signal
level has everything to do with Class A operation, and in turn defines
maximum possible dissipation from Class A operation. Cruise my
netsite; all this is explained in both words and pictures.
Andre Jute
Mmm. It occurs to me that when dealing with a newbie, even if it is
all explained on my netsite, and Patrick's, and all the textbooks, and
in Crowhurst, which Multi-grid could read with profit, I should
explain what signal voltage has to do with power output. Power is the
product of voltage and current. The bigger the voltage and current
swing, the greater the power output (for a given load). The plate
voltage and current swing is proportional to the size of the signal
working through mu, the amplification factor of the tube. Thus the
greater the signal that can be put in under a particular class of
operation, in this case Class A, the greater the voltage swing and the
more the current change between the peaks of the signal, the bigger
the product of voltage and current, and the greater the power. So, you
see, sonny, in Class A operation, which is in any event very
inefficient, the amount of space the designer allows for signal to
swing without breaching Class A conditions determines the entire
outcome. The same applies to Class AB, where the signal-travel the
designer has arranged (by his choice of plate voltage and negative
grid bias and primary impedance) during which current is not cut off
determines how much of the output can be in Class A, with the rest by
definition in Class B.
> Andre Jute
> Visit Jute on Amps athttp://members.lycos.co.uk/fiultra/
Multi-grid
>
> - Show quoted text -- Hide quoted text -
>
> - Show quoted text -
keep repeating yourself, it may come true sometime.
In the meantime, some additional proof besides the circular stuff you
keep digging up might show you the holes in your arguement. As to
Crowhurst, his creativity outstripped his ability to write
unequivocally.
While you're digging, why not produce some documentation of the 80W SE
amp you mentioned earlier.
cheers,
Douglas
Multi-grid
They don't Andre, no matter how much you claim they do. Class A, is as
simple as you first stated it:
***Class A operating conditions do not permit the output device to
> cease conducting.***
It should get the addition that remote cut off behaviour is not
included.
In particular, you should pay attention to
> this, which often comes as a bolt from the blue to repair hacks like
> you, who tend to assume that the parameters are godgiven and fixed:
> the *designer* chooses the plate voltage and negative bias, that sets
> the current at quiescence, through which the designer then runs the
> loadline at a particular angle when he chooses a primary impedance for
> his output transformer, the slope of the loadline determining how far
> the quiescent point is from current cutoff (or voltage cutoff...), and
> that in turn defines the signal voltage that can be put in for Class A
> operation, which in turn defines the output power. Thus the signal
> level has everything to do with Class A operation, and in turn defines
> maximum possible dissipation from Class A operation. Cruise my
> netsite; all this is explained in both words and pictures.
I make no such assumptions. That you'd think I would only shows your
limitations. Stay off this group-killing personal attacking if you
please. Isn't one war named after you enough?
cheers,
Douglas
John Byrns
Multi-grid <pen...@netscape.com> wrote:
> On Oct 24, 1:37 am, Andre Jute <fiul...@yahoo.com> wrote:
> >
> > As for Dougles Multi-grid's silly insistence that signal and
> > dissipation have nothing to do with Class A operation, thanks for the
> > giggle, sonny, but you'd better hit the books lots more before you
> > seek entry to this club.
>
> They don't Andre, no matter how much you claim they do. Class A, is as
> simple as you first stated it:
>
> ***Class A operating conditions do not permit the output device to
> cease conducting.***
Precisely, that is why when the operating conditions of a class AB
amplifier are restricted by limiting the applied input voltage the
amplifier is able to put out class A power at a level that is lower than
the maximum available class AB power.
> It should get the addition that remote cut off behaviour is not
> included.
Most real world tubes display remote cut off behaviour as the plate
curves become distinctly compressed in the high voltage low current
quadrant. I guess that rules out the possibility of any tube amplifier
operating class A.
Peter Wieck
> In article <1193187178.244971.90...@k35g2000prh.googlegroups.com>,
>
> Multi-grid <pent...@netscape.com> wrote:
> > On Oct 24, 1:37 am, Andre Jute <fiul...@yahoo.com> wrote:
>
> > > As for Dougles Multi-grid's silly insistence that signal and
> > > dissipation have nothing to do with Class A operation, thanks for the
> > > giggle, sonny, but you'd better hit the books lots more before you
> > > seek entry to this club.
>
> > They don't Andre, no matter how much you claim they do. Class A, is as
> > simple as you first stated it:
>
> > ***Class A operating conditions do not permit the output device to
> > cease conducting.***
>
> Precisely, that is why when the operating conditions of a class AB
> amplifier are restricted by limiting the applied input voltage the
> amplifier is able to put out class A power at a level that is lower than
> the maximum available class AB power.
>
> > It should get the addition that remote cut off behaviour is not
> > included.
>
> Most real world tubes display remote cut off behaviour as the plate
> curves become distinctly compressed in the high voltage low current
> quadrant. I guess that rules out the possibility of any tube amplifier
> operating class A.
John, with respect:
Andre is out of his depth on this one. And his typical response to
being out of his depth is to repeat, attack, repeat, attack, and then
repeat again. But none of that makes what he states true or correct.
And as your life's work is somewhere between cleaning up after him,
powdering him and changing his diapers and seeking exceptions and
outliers, I am not surprised that you are joining this discussion as
per usual.
There have actually been some reasonable discussions on tube lore
lately - those from which Andre has stayed away. And, were he to
refrain from delivering (typically incorrect) absolutes he might even
be capable of intiating and even participating in such discussions.
But, it is very hard for a pretender to stick to what he knows and for
a poseur to pronounce with less than "papal" infallibility. Which
makes Andre little more than a charlatan and never-was with delusions
of adequacy. All-and-at-the-same-time, he is a big boy of some 60+
summers and well able to manage his own affairs and discussions... or
it would be so were he mature enough to understand. Infants usually
and eventually become potty-trained. And that is the essential
difference between Andre and an infant, and why your efforts at clean
up after him are futile. He will never change however heroic your
efforts.
If you want an analogy, GM, some time back had a V8 engine that
*could* fire on 4, 6, or 8 cylinders depending on load conditions. But
it was never "other than" a V8, nor could any amount of wishful
thinking or closely held beliefs make it "other than" a V8.
Peter Wieck
Wyncote, PA
Patrick Turner
Class A has everything to do with dissipation!!!!
But lets begin with class B.
In class B, there is ZERO anode dissipation because the tubes ( or SS
devices )
are biased at cut off. The amplifier only has device dissipation when
signal flows.
But distortion is notoriously high, and to avoid the worst of it, class
AB is used
where the tubes/devices are biased with idle dissipation well below the
maximum allowable fpr the tube or device.
This allows a small amount of pure class A working power until cut off
begins to occur in tubes/devices
on each alternate wave peak.
Hence a pair of KT88 might be set up with Ea = 600V, and Ia at idle of
30mA, for a Pda at idle
of 18 watts. Maximum allowable for a single KT88 is 42 watts.
The AB power avaliable with 600V is around 100Watts class AB but the
pure class A might be less than 10 watts
for the load where 100Watts AB is possible, which will be a load a lot
less than the load required for
pure class A operation up to clipping.
Its possible to have two KT88 dissipating a total of 36 watts, Ea =
600V, and have a load which ensures all the power
is class A. It is a high ohm load, but achievable if you connect a 16
ohm speaker to an AB amp with an outlet
for 4 ohms; the reflected anode load of say 5k becomes 20k.
And the beam terode class A efficiency will be up to about 45% and so
you'll get a maximum
of 16.2 watts of pure class A power from a pair of KT88 with a total of
36 watts Pda.
If the Pda is raised to 72 watts for the pair by doubling the Ia, then
max class A
also doubles if efficiency is constant, so 36 watts is possible.
The load can be a lot lower as well.
I suggest you learn much more about basic output tube behaviour before
you shoot your mouth off
by saying that " Class A has nothing to do with dissipation either. "
Just because some
> marketing group noticed that class A means something good, does not
> make it right either. Just because it seems to make sense is no reason
> to bastardize the definition. Find some other way to describe it.
> cheers,
> Douglas
You are looking like the one bastardizing something imho.
Please clarify your reasons for whatever your stance really is.
Patrick Turner.
Patrick Turner
It means slightly more than this because tubes don't cut off as sharply
as other devices.
So class A means where PP power tubes do not have Ia on either side of
the PP circuit ever
having Ia fall below 10% of the idle value.
Below about 10% of the idle value, the cut off behaviour becomes
substantially non linear, as opposed to substantially linear prior to
cut off.
Gradual cut off in triodes makes them particularly nice to use in AB
amps.
Minimal switching artifacts are generated. And the gm rises with Ia, so
the
load change reduction happening after cut off of one tube means the
triode compensates for the sudden drop in gain you see in pentodes and
beam tubes.
Its the internal triode NFB at work to give the low Ra.
And if the first 1/2 of output power maximum is class A by my
definition, then is its deemed A,
and the remaining 1/2 is B, and the total action is AB.
Most ppl will not hear any difference if the bias is increased to ensure
all power
up to clipping is pure class A.
The load experienced by one of the tubes in an AB PP pair is NOT a
straight line load
as one would draw across the anode curves of a given tube.
While in class A, each tube sees an almost straight line load, but
always of slightly
different ohm value because the gm of each tube isn't the same.
But the RL for each tube while in class A is approximately 1/2 of
RLa-a.1
Once cut off has begun in earnest during each wave cycle, the load each
tube sees
become its "class B load" = 1/4 RLa-a, and one has to draw a CURVED LOAD
LINE to describe the loading
of each PP output tube to describe what each is really doing.
The load of one tube is affected by the load on the other until cut off
happens,
and then each tube is on its own to deal with the load of 1/4 RLa-a.
Patrick Turner.
> Graham
Multi-grid
> >
>
Class A, is as simple as you first stated it:
>
> ***Class A operating conditions do not permit the output device to
>
> > cease conducting.***
>
> It should get the addition that remote cut off behaviour is not
> included.
>. Isn't one war named after you enough?
> - Show quoted text -
sorry about that, forgot one thing...That is *AT FULL POWER*, if one
gets cut off before that, it is AB, which is neither A nor B.
cheers,
Douglas
Multi-grid
>
> I suggest you learn much more about basic output tube behaviour before
> you shoot your mouth off
> by saying that " Class A has nothing to do with dissipation either. "
>
>
> - Show quoted text -
The dissipation is only related to the output power. A Class A amp
does not need a particular fraction of plate dissipation to be used in
order to classify as A. Examples are not needed, symbolic notation
will be fine.
The amp is defined by its behaviour. The bias that goes from 360-
degree conduction to something closer to 180 gets labled AB. Iff it
can maintain 360 degree conduction it gets the A.
Since it's usually quality over max power choices that run to class A
designs, the marketers decide to appropriate it for their own in AB
designs. You remember the advertisements general content( reference
Andre's comments on the Vellman ).
B is supposedly 180 degree, but given cut-off bunching, none are that
small. Why not have this discussion about the differences between AB
and B?
cheers,
Douglas
Eeyore
Patrick Turner wrote:
> Eeyore wrote:
> > Multi-grid wrote:
> > > maxhifi <n...@spam.com> wrote:
> > >
> > > > Stating that "the amplifier is Class A until XXX watts", really, is
> > > > telling you how hot the tubes are biased relative to the two extremes of
> > > > pure class A (full dissapation), and pure class (cut off).- Hide quoted text -
> > >
> > >
> > > Class A has nothing to do with dissipation either. Just because some
> > > marketing group noticed that class A means something good, does not
> > > make it right either. Just because it seems to make sense is no reason
> > > to bastardize the definition. Find some other way to describe it.
> >
> > The definition of Class A is very simple. It requires that the output device(s)
> > never cease conducting under any signal condition.
>
> It means slightly more than this because tubes don't cut off as sharply
> as other devices.
I see what you're saying but I do believe that the definition is unchanged. Obviously
avoiding any region of significant non-linearity is preferable but that in its own right
doesn't change the definition.
Graham
John Byrns
Peter Wieck <pf...@aol.com> wrote:
> On Oct 23, 8:51 pm, John Byrns <byr...@sbcglobal.net> wrote:
> > In article <1193187178.244971.90...@k35g2000prh.googlegroups.com>,
> >
> > Multi-grid <pent...@netscape.com> wrote:
> >
> > > ***Class A operating conditions do not permit the output device to
> > > cease conducting.***
> >
> > Precisely, that is why when the operating conditions of a class AB
> > amplifier are restricted by limiting the applied input voltage the
> > amplifier is able to put out class A power at a level that is lower than
> > the maximum available class AB power.
>
> John, with respect:
>
> Andre is out of his depth on this one.
Peter, I know you are obsessed with Andre, but this is not about Andre,
it is about Multi-grid's silly statement that a class AB amplifier can't
put out a limited amount of "class A power". Multi-grid is confusing
the definition of a PP amplifier's class with it's ability to deliver
some amount of power, less than rated output, without either output tube
cutting off. It has been common usage for as long as I can remember to
call this "class A power" because at this power level both output tubes
are conducting over the full 360 degree cycle, as in a class A
amplifier. An amplifiers class is determined by the operation of the
tubes at the rated power output, however in the case of a class AB
amplifier, a lesser amount of "class A power" is available.
To illustrate how silly Multigrid's claim is, consider a class AB
amplifier with a rated output of 50 Watts in class AB. Further suppose
this amplifier is capable of putting out 15 Watts without either output
tube cutting off, 15 Watts of what Andre, and many other famous
amplifier designers, call "class A power". Now we all agree that this
is a class AB amplifier, but suppose we connect a suitable network of
Zener and ordinary diodes across the primary of the output transformer
which clamp the maximum output voltage at the level necessary to produce
an output of 15 Watts. Has this amplifier now become a class A
amplifier simply because we have placed this clamp circuit across the
primary of the output transformer? If we test it with our sine wave
generator and oscilloscope we are going to conclude that it is a class A
amplifier because both tubes are still conducting over the full 360
degree cycle at the point of clipping. I leave the implications of this
experiment for the student to consider.
Andre Jute
> On Wed, 24 Oct 2007 13:44:13 +0100, Eeyore
> the definition of the 'amplifier' class while others are speaking of
> it's behavior under a restricted set of operating conditions; and it
> is useful to observe that under an appropriately restricted set of
> conditions the output tubes conduct 360 degrees as in 'Class A'
> operation.
"Useful", indeed, Flipper. Thanks. But I would go further and say that
the signal and dissipation restriction is part of the definition, as
you go on to imply:
> For example, if maximum power, or efficiency, were the primary concern
> then one might bias more to the 'B' side of the equation while if
> fidelity were the primary concern one might bias more to the 'A'.
Precisely. Both Class A operation and Class B operation are inherent
in the nomenclature and definition and their relative importance is
clearly intended to be in the designer's discretion.
Historically, the original purpose of Class AB was to annihilate the
second harmonic which before made up such a very large part of the
THD, while still allowing beam tubes and pentodes to give much larger
power than available before. The "invention" of Class AB as a hi-
fidelity amp is what spurred part of a Olsen's work on perception;
before it wasn't known that odd harmonics are proportionately much
more disturbing than even harmonics. It seems to me that AB amps with
largish parts of their output in Class A is a relatively modern trend,
possibly related to ever less-sensitive speakers.
> One might also observe that's likely why it's called Class AB and not
> Class <insert unique letter>.
There is in fact a class between Class A and Class AB with a unique
description: "Limiting Class A1", which is set up so that the
crossover happens when one valve just reaches current cutoff and the
other simultaneously reaches zero bias. It makes for an amazingly
smooth sound but it is a bitch to set up and keep tuned if you want to
keep your circuits simple. I was therefore rather interested in what
Patrick said elsewhere in this thread (in more general sense rather
than specifically about LImitiing Class A1) about within 10 per cent
of conduction angle being imperceptible...
Andre Jute
Visit Jute on Amps at http://members.lycos.co.uk/fiultra/
Andre Jute
wrote:
Let's look at your definition again:
Poopie Stevenson wrote:
> > The definition of Class A is very simple. It requires that the output device(s)
> > never cease conducting under any signal condition.
Why don't you explain to us how a Class A amp can operate within the
class "under any signal condition", which presumably includes *much*
larger signals than the negative bias?
Your definition ipso facto makes Class A an impossible operating
condition because an increasing level of signal, permitted "under any
signal condition", will sooner or later drive the amp into cutoff. Of
course, long before then it will cease to be a high fidelity
amplifier, though, on the evidence of your posts, we don't expect that
to matter to you.
I repeat, a Class A amp, including that part of a Class AB amp
operating in Class A, are always and under any circumstances subject
to the designer's input signal limit or, if instead stated,
dissipation limit. To demand that a Class A amplifier work "under any
signal condition" is stupid for even a newbie, never mind someone like
you, Graham Stevenson, who claims to design electronic gear for sound
professional to use.
Peter Wieck
> Technically correct stuff snipped.
John:
I agree with what you say inasmuch as it is *absolutely* technically
correct. But the amplifier you posit is still a Class AB unit and/or a
unit that has been modified to make only Class A - and therefore NOT a
Class AB unit anymore - and as a 'modified' A not really all that hot-
sh*t an A either?
Point being that the GM V8 remains a V8 even though it is *capable* of
operating in 4 or 6 cylinder modes - albeit at much a much reduced PtW
ratio. And it could also be modified with a suitable network of
controls to remain in either 4 or 6 cylinder mode at all times - and
therefore *technically* be described as a 4 or a 6. It is certainly
not anyone's idea of a V8 anymore - nor what should be a good idea of
a 6 or 4.
Which, of course, would be a 100% marketing ploy, wouldn't it? To call
it a 4 or a 6 by virtue of the modifications?
As a purpose-built 4 or 6 would be a much better solution, wouldn't
it?
And that same purpose-built 4 or 6 could be made with the same
displacement, potential output HP and torque as a V8, couldn't it?
And that would, of course, cost a pretty penny - more than a similar
displacement & output V8? Large output Class A (tube) amps tend to be
costly, right?
So, an amplifier *may* operate in Class A mode for some range based on
its design. But it cannot, must not, nor should it be classified as a
Class A amp if it does not operate in Class A at all ranges.
Otherwise, what we have is a marketing ploy because as previously
stated: Class A = Good Class AB = Not So Good
All classes of amplifiers are equal, some are more equal than others.
Unless similar Orwellian terms apply, then the principle of the
excluded middle applies. Can't have it both ways.
I am not trying to be simplistic, just clear on what is meant and what
is implied. As things look from the discussion here, only Patrick is
discussing this with Douglas on equal terms. And I have a sense that
they agree more than they disagree. Andre has a bug up his butt - as
always - and therefore cannot discuss much of anything on any
reasonable terms. He really should step out of it and enjoy the
discussion as it is being pursued by his betters - I am certainly
watching it with interest. And the side issue of all this is that
between George, Bret and Andre, the atmosphere in this NG has been
pretty toxic of late. Maybe all three of them should take a rest and
let the air clear... although I do have my doubts as to George being a
discrete individual and not a sock-puppet.
Peter Wieck
Wyncote, PA
John Byrns
Andre Jute <fiu...@yahoo.com> wrote:
> Historically, the original purpose of Class AB was to annihilate the
> second harmonic which before made up such a very large part of the
> THD, while still allowing beam tubes and pentodes to give much larger
> power than available before.
Andre, why was Class AB necessary to annihilate the second harmonic,
didn't Push Pull operation already annihilate the second harmonic
irrespective of the class of operation?
> The "invention" of Class AB as a hi-
> fidelity amp is what spurred part of a Olsen's work on perception;
> before it wasn't known that odd harmonics are proportionately much
> more disturbing than even harmonics. It seems to me that AB amps with
> largish parts of their output in Class A is a relatively modern trend,
> possibly related to ever less-sensitive speakers.
I'm not sure I would agree with that, class AB amps were common even in
the days of efficient speakers, I don't see it as "a relatively modern
trend", if anything is a modern trend, I would think it is the return to
"pure" class A amplifiers on the part of many audiophiles.
John Byrns
Peter Wieck <pf...@aol.com> wrote:
> On Oct 24, 10:48 am, John Byrns <byr...@sbcglobal.net> wrote:
>
> > Technically correct stuff snipped.
>
> John:
>
> I agree with what you say inasmuch as it is *absolutely* technically
> correct. But the amplifier you posit is still a Class AB unit and/or a
> unit that has been modified to make only Class A - and therefore NOT a
> Class AB unit anymore - and as a 'modified' A not really all that hot-
> sh*t an A either?
>
> Point being that the GM V8 remains a V8 even though it is *capable* of
> operating in 4 or 6 cylinder modes - albeit at much a much reduced PtW
> ratio.
The GM 4-6-8 is not a good analogy because it has 8 cylinders even when
only 4 are operating. The class A vs. class AB amplifier is a different
situation because the only fundamental difference between the two is the
setting of the bias pot. If you ask nicely I might go in to some of the
non essential differences between the two.
> I am not trying to be simplistic, just clear on what is meant and what
> is implied. As things look from the discussion here, only Patrick is
> discussing this with Douglas on equal terms.
I wouldn't put Douglas, a.k.a. Multi-grid, on equal terms with Patrick.
> And the side issue of all this is that
> between George, Bret and Andre, the atmosphere in this NG has been
> pretty toxic of late. Maybe all three of them should take a rest and
> let the air clear... although I do have my doubts as to George being a
> discrete individual and not a sock-puppet.
Who is "George", I haven't noticed anyone, "discrete individual" or
"sock-puppet", by that name participating in this discussion?
Andre Jute
> In article <1193187178.244971.90...@k35g2000prh.googlegroups.com>,
>
> > On Oct 24, 1:37 am, Andre Jute <fiul...@yahoo.com> wrote:
>
> > > As for Dougles Multi-grid's silly insistence that signal and
> > > dissipation have nothing to do with Class A operation, thanks for the
> > > giggle, sonny, but you'd better hit the books lots more before you
> > > seek entry to this club.
>
> > They don't Andre, no matter how much you claim they do. Class A, is as
> > simple as you first stated it:
>
> > ***Class A operating conditions do not permit the output device to
> > cease conducting.***
>
> Precisely, that is why when the operating conditions of a class AB
> amplifier are restricted by limiting the applied input voltage the
> amplifier is able to put out class A power at a level that is lower than
> the maximum available class AB power.
>
> > It should get the addition that remote cut off behaviour is not
> > included.
>
> Most real world tubes display remote cut off behaviour as the plate
> curves become distinctly compressed in the high voltage low current
> quadrant. I guess that rules out the possibility of any tube amplifier
> operating class A.
In the halflight dreamworld inhabited by Dougles Zero-sound, Poopie
Stevenson and Worthless Wiecky, SE amps would be impossible, Class A1
amps would be impossible, and all other classes would produce zero
music -- in fact all other classes would produce 100 per cent pure
noise by being operated at all sonic peaks at either max current and
zero voltage or zero current and voltage plate overvoltage. All of
that follows logically from Poopie's absurd redefinition of Class A as
a Class in which "the output device(s)never cease conducting *under
any signal condition*," (emphasis added). It's ludicrous. Any amp can
be driven out of class by excessive signal voltage. That clown Poopie
Stevenson has overreached himself again; Dougles Multi-grid is an
ignorant (and impertinent) troll of a kind well known on RAT; poor
Witless Wiecky is just another know-nothing garage trader who wantst
to move up to repair hack status.
This whole affair is nuts. We're wasting our time arguing with people
who will say anything to put someone down, regardless of the known
facts of physics. I've always known that Poopie and Worthless are
ineducable on any timescale less than glacial. Dougles Zero-sound is
clearly another veeeeery sloooow learner. The stubborn lack of
sophistication in his ignorance makes me nostalgic for Pasternack, who
at least sometimes said something interesting as he twisted this way
and that in the web of his lies; at the very least Plod never would
have been dumb enough to attempt lying about something as simple as
operating classes.
> Regards,
>
> John Byrns
>
> --
> Surf my web pages at, http://fmamradios.com/
One has to laugh. The alternative is unthinkable...
Peter Wieck
Please note the interpolations:
On Oct 24, 1:53 pm, John Byrns <byr...@sbcglobal.net> wrote:
> The GM 4-6-8 is not a good analogy because it has 8 cylinders even when
> only 4 are operating. The class A vs. class AB amplifier is a different
> situation because the only fundamental difference between the two is the
> setting of the bias pot. If you ask nicely I might go in to some of the
> non essential differences between the two.
Mpffff... of course. But you postulated the series of zeners and so
forth so as to make an as-designed AB into a pure Class A amp. From
that, all else follows. Many things can be done - the question is
whether they should be done to that amp and if done would the results
be better/worse/as-good as if purpose-designed from the ground up.
Otherwise, one is forcing the proverbial square peg into the legendary
round hole.
> I wouldn't put Douglas, a.k.a. Multi-grid, on equal terms with Patrick.
Discussing on equal terms - not necessarily on equal terms overall.
> Who is "George", I haven't noticed anyone, "discrete individual" or
> "sock-puppet", by that name participating in this discussion?
Middius, and not necessarily in this discussion, but certainly part of
the general miasma.
Fly poop on the right, pepper on the left.
Peter Wieck
Wyncote, PA
Eeyore
John Byrns wrote:
> Andre Jute <fiu...@yahoo.com> wrote:
>
> > Historically, the original purpose of Class AB was to annihilate the
> > second harmonic which before made up such a very large part of the
> > THD, while still allowing beam tubes and pentodes to give much larger
> > power than available before.
>
> Andre, why was Class AB necessary to annihilate the second harmonic,
> didn't Push Pull operation already annihilate the second harmonic
> irrespective of the class of operation?
Yes, you are right. It does.
The SOLE purpose of AB is to produce larger power outputs using the same tubes.
The dissipation in the output tubes is very considerably lower than that in
Class A.
Graham
Eeyore
Andre Jute wrote:
> In the halflight dreamworld inhabited by Dougles Zero-sound, Poopie
> Stevenson and Worthless Wiecky, SE amps would be impossible, Class A1
> amps would be impossible, and all other classes would produce zero
> music -- in fact all other classes would produce 100 per cent pure
> noise by being operated at all sonic peaks at either max current and
> zero voltage or zero current and voltage plate overvoltage. All of
> that follows logically from Poopie's absurd redefinition of Class A as
> a Class in which "the output device(s)never cease conducting *under
> any signal condition*," (emphasis added). It's ludicrous.
It's actually the only accurate definition.
> Any amp can be driven out of class by excessive signal voltage.
Overdriving to cut-off is merely gross abuse and a complete red herring /
irrelevance.
You really should constrain yourself to talkind about stuff you understand.
Which would seem not to be very much going by your posting history.
Graham
Eeyore
flipper wrote:
> Eeyore <rabbitsfriend...@hotmail.com> wrote:
> >Andre Jute wrote:
> >
> >> In the halflight dreamworld inhabited by Dougles Zero-sound, Poopie
> >> Stevenson and Worthless Wiecky, SE amps would be impossible, Class A1
> >> amps would be impossible, and all other classes would produce zero
> >> music -- in fact all other classes would produce 100 per cent pure
> >> noise by being operated at all sonic peaks at either max current and
> >> zero voltage or zero current and voltage plate overvoltage. All of
> >> that follows logically from Poopie's absurd redefinition of Class A as
> >> a Class in which "the output device(s)never cease conducting *under
> >> any signal condition*," (emphasis added). It's ludicrous.
> >
> >It's actually the only accurate definition.
> >
> >> Any amp can be driven out of class by excessive signal voltage.
> >
> >Overdriving to cut-off is merely gross abuse and a complete red herring /
> >irrelevance.
>
> It's not a 'red herring' when you clearly stated "under any signal
> condition."
Do you normally operate amplifiers into gross distortion ? I was trying to avoid
the '360 degree' terminology which kind of implies for its part, sinewave only
use.
Do please, if you desire, change it to 'any valid signal condition for which the
amplifer is rated'.
Graham
Multi-grid
>
> Historically, the original purpose of Class AB was to annihilate the
> second harmonic which before made up such a very large part of the
> THD, while still allowing beam tubes and pentodes to give much larger
> power than available before. .
>
> >
>
>
>
> - Show quoted text -
Well Andre, you've stepped in it this time...:) AB operation cannot
effectively cancell *ANYTHING*.
Odd sums anyway.
Not second HD( or the even of any order ) because each phase is biased
where the characteristics are changing too rapidly with plate current.
This is the rest of the Class A definition that is implied, the finals
are biased so that the change in characteristic for the opposing
phases approximately cancells( and thus the even HD ). It is why the
AB amp can't be labled A while both phases of the finals are
conducting( or that that single definition is not enough to describe
Class A ).
The x power in A, and XXX power in AB is just serving notice that
marketing had its way with the ad copy.
AB was an obvious means of minimizing cross-over distortion and
maximizing power. It works just as well for directly heated triodes
with no NFB as it does for pentodes like the KT88 running a lot of
it...:)
cheers,
Douglas
Peter Wieck
On Oct 24, 3:42 pm, flipper <flip...@fish.net> wrote:
> This is what I meant. People seem to be losing track of who said and
> meant what.
I am not so sure that losing track is the correct description of what
is going on. It more-or-less started with a statement that a Certain
Amp was a Model for various reasons amongst which was an apparent
broad Class A operational range before it went to AB.
> >So, an amplifier *may* operate in Class A mode for some range based on
> >its design.
>
> I may have missed something but as far as I can tell *that* is the
> 'argument'.
I don't think anyone would disagree even for a hummingbird heartbeat
that some AB amps have some range of A operation before they go AB. It
is how one would describe and represent the amp overall that is at
issue.
> > But it cannot, must not, nor should it be classified as a
> >Class A amp if it does not operate in Class A at all ranges.
>
> I haven't seen anyone claim that a Class AB amp is 'actually' a Class
> A amp, or should be 'classified' as an 'A' something, or any variation
> of the theme.
>
> >Otherwise, what we have is a marketing ploy because as previously
> >stated: Class A = Good Class AB = Not So Good
>
> I think you're worrying about something that no one in here is guilty
> of and, near as I can tell, the 'argument' revolves around the claim
> by Multi-grid:
>
> "That both tubes are conducting does not mean it is
> A. Have some respect...:) AB amps don't have any A power, that is why
> there is a separate classification."
> It would seem to me that with your comment above saying "an amplifier
> *may* operate in Class A mode for some range" that you are disagreeing
> with Multi-grid.
I do not necessarily agree with Douglas. I just find the rebuttals to
his statements mostly either technically inept (as from Andre) or
technically elegant (as from John) but beside the point.
> Btw, just as a matter of discussion, I see where you're trying to go
> with the V8 analogy but I don't think it holds, as given, because 2,
> 4, 6, and 8 cylinder operation is not a 'natural' consequence of the
> 'engine class V8' while 'A' and 'B' (loosely defined) are for 'Class
> AB'.
Actually, it was John that postulated a series of controls on an AB
amp that would force it (hold it in) to A class only. So, the analogy
of an 8 held to 4 or 6 cylinders only holds under that description.
> I think a closer, albeit still 'stretched' quite a bit, analogy would
> be if we defined 'engine classes' 4, 8 and "4-8," and then pondered if
> a 'Class 4-8' engine was operating 'Class 4' during the times when
> only 4 of the cylinders were firing. If the definition for 'Class 4'
> was "4 cylinders firing" then one might say it was, despite some
> differences, since 4 cylinders are firing under those conditions; Akin
> to 'Class A' being the tubes conducting 360 degrees, a situation that
> occurs in Class AB amps under certain conditions.
Oh, the entire engine analogy is stretched more than taffy on a hot
day in Atlantic City. But for all that, it is as valid as any other
points made along the line in this particular thread - again excepting
the direct contributions from Patrick which are right into the nitty-
gritty of the situation.
> And one might wish to talk about under what conditions the 'Class 4-8'
> engine makes the transition from 'Class 4' to 'Class 8' operation
> because if it did so at the slightest hint of needing more power it
> might make for 'zippy' performance at the expense of fuel efficiency
> while a 'Class 4-8' engine reluctant to do so might be more efficient
> at the expense of 'zippy' throttle response. But, IMO, saying "it's
> Class 4-8, period, there is no Class 4 power" simply serves to obscure
> it's operation for no useful purpose.
Well, it ain't nohow a "4-only" and it ain't nohow an "8-only", so it
must be something else. The only accurate label would be a "4-8". That
it operates in either mode is a function of its design. But it belongs
to neither unique class.
> It might also be useful to point out, as you did, that 'Class 4'
> operation of a 'Class 4-8' engine is not '100% equivalent' to 'Class
> 4' operation in a true 'Class 4' engine (depending on how well
> designed each is) because you're dragging along dead cylinders, a
> necessary consequence of it being a 'Class 4-8' engine, and, by the
> same token, 'Class A' operation in a Class AB amp is not '100%
> equivalent' to a true Class A amplifier (depending on how well
> designed each is) for the same reason: the 'Class A' region of a Class
> AB amp is compromised by the necessities of it being a Class AB amp.
Yep. And that is contributory to the point but not critical to it.
> However, there's nothing in the 'Class' definitions that speaks to
> 'optimal', 'well designed', or 'equivalencies'.
Amen to that! There is quite a bit of ineffable crap out there. Some
of it is very expensive and uses very expensive boutique-type tubes
for no other reason than that they are expensive boutique tubes -
certainly not for the quality of the signal coming out of them. Why,
even their makers and defenders will wax poetic about how these amps
"add coloration" to the signal that makes them an "instrument in their
own right" and such twaddle. It is those sorts who will wax poetic
about that little bit of "Class A" operation in an AB-designed amp as
some great virtue. In point of fact, this would necessarily require
that the AB operation of the same amp is somehow faulty. Otherwise a
properly designed amp would be A only and t'h*ll with the headroom.
Once again, unless we are dealing in an Orwellian world, it just isn't
necessarily so.
Peter Wieck
Wyncote, PA
John Byrns
Peter Wieck <pf...@aol.com> wrote:
> It is those sorts who will wax poetic
> about that little bit of "Class A" operation in an AB-designed amp as
> some great virtue. In point of fact, this would necessarily require
> that the AB operation of the same amp is somehow faulty. Otherwise a
> properly designed amp would be A only and t'h*ll with the headroom.
I don't see how the one follows from the other, could you please explain
the logic you used in arriving at this conclusion?
John Byrns
Peter Wieck <pf...@aol.com> wrote:
> Point being that the GM V8 remains a V8 even though it is *capable* of
> operating in 4 or 6 cylinder modes - albeit at much a much reduced PtW
> ratio. And it could also be modified with a suitable network of
> controls to remain in either 4 or 6 cylinder mode at all times - and
> therefore *technically* be described as a 4 or a 6. It is certainly
> not anyone's idea of a V8 anymore - nor what should be a good idea of
> a 6 or 4.
>
> Which, of course, would be a 100% marketing ploy, wouldn't it? To call
> it a 4 or a 6 by virtue of the modifications?
I'm not sure it was a pure marketing ploy, especially given that I have
seen ads for a current model car that uses this same idea today,
unfortunately I forget what car it is, it might even be a Cadillac,
although I would think they would be too gun shy to try it again. At
any rate the reason I started this sub thread was to ask if anyone more
knowledgeable about engines than you or I knows the theory of the 8-6-4
engine and how it was supposed to improve gasoline mileage, which as I
remember it was what the hype said it was supposed to do? The only
potential efficiency gain that I can see is that it would presumably
reduce throttling losses a bit, but there must be more to it than just
that, does anyone know? I guess I should ask Google.
> As a purpose-built 4 or 6 would be a much better solution, wouldn't
> it?
Better solution for what problem?
> And that same purpose-built 4 or 6 could be made with the same
> displacement, potential output HP and torque as a V8, couldn't it?
Yes, but a 4 cylinder engine with the power of a V8 might be a little
rough for many Cadillac buyers.
> And that would, of course, cost a pretty penny - more than a similar
> displacement & output V8?
I would expect that a V8 would cost more than a 4 of similar
displacement, simply based on the parts count, but what do I know. The
4 would probably require some more expensive drive train parts than the
V8, at least in manual transmission applications.
John Byrns
Multi-grid <pen...@netscape.com> wrote:
> Well Andre, you've stepped in it this time...:) AB operation cannot
> effectively cancell *ANYTHING*.
>
> Odd sums anyway.
Thanks for that clarification.
> Not second HD( or the even of any order ) because each phase is biased
> where the characteristics are changing too rapidly with plate current.
> This is the rest of the Class A definition that is implied, the finals
> are biased so that the change in characteristic for the opposing
> phases approximately cancells( and thus the even HD ).
That's a bunch of nonsense and drivel, if the cancellation were simply
the result of "the finals are biased so that the change in
characteristic for the opposing phases approximately cancels", then the
amount of odd order distortion could also be changed by PP connection.
The fact is that the even order cancellation is not dependent on the
biasing of the tubes, beyond the requirement that the two tubes are
identical and are both biased the same.
Check your High School Trigonometry book to understand why the even
harmonics cancel while the odd ones don't, it's a simple bit of math
that doesn't depend on bias, only that the two sides of the PP circuit
are identical. IIRC even PP class C amplifiers cancel even order
distortion, this was made use of in early FM broadcast transmitters to
minimize interference with high band VHF Television stations, without
the need for a harmonic filter in the output of the FM transmitter.
> It is why the
> AB amp can't be labled A while both phases of the finals are
> conducting( or that that single definition is not enough to describe
> Class A ).
It isn't obvious by what logic you arrived at that conclusion?
> The x power in A, and XXX power in AB is just serving notice that
> marketing had its way with the ad copy.
You aren't by any chance one of Peter Wieck's sock-puppets are you?
> AB was an obvious means of minimizing cross-over distortion
Class AB simply moves the crossover notch up to a higher amplitude point
on the signal waveform, if you really want to minimize the crossover
notch you should have Patrick design and wind you an OPT designed
specifically to minimize the crossover notch, or go with a McIntosh
design.
> and maximizing power.
Class B operation would be even better for maximizing power.
> It works just as well for directly heated triodes
> with no NFB as it does for pentodes like the KT88 running a lot of
> it...:)
Yep, it sure is great stuff!
Andre Jute
> In article <1193239797.164883.169...@k35g2000prh.googlegroups.com>,
> Andre Jute <fiul...@yahoo.com> wrote:
>
> > Historically, the original purpose of Class AB was to annihilate the
> > second harmonic which before made up such a very large part of the
> > THD, while still allowing beam tubes and pentodes to give much larger
> > power than available before.
>
> Andre, why was Class AB necessary to annihilate the second harmonic,
> didn't Push Pull operation already annihilate the second harmonic
> irrespective of the class of operation?
Well, yes, but who would want a strictly Class B tube amp? It'll be
harsh and nasty and the THD will be grim. On the other hand, there was
an urgent demand (possibly only from the marketing department,
possibly from speaker manufacturers -- these things are very rarely
consumer-led) for more output than available from SE or even Class A
triodes. Class AB, a natural for the new multi-grid tubes, was for the
time a perfect compromise between the "waste" of Class A and the (at
the time) incredible power available from push-pull operation of beam
tubes and pentodes, *and* Class AB had a lower NFB requirement than
Class B, all others things being equal of course, and thus better
stability margins. All of this happened at the same time ever-lower
THD numbers became the chief marketing tool; it followed in turn that
the THD should be attacked where it was most vulnerable and where it
would give the biggest fix in the least time for the lowest cost, and
that was at the second harmonic. So, you don't want Class B because it
is crude, you can't have Class A because it is too expensive for the
power you want, you must have a lot of stable power with low THD,
bingo, Class AB saves your butt. You have to look at the entire
package of elements that drove the general swing towards Class AB.
Having looked, from a closer vantage point than ours, at the package
of elements, Langford-Smith himself tells us in the RDH4 (Newnes
1997) on p 545 that:
"Class AB operation indicates overbiased conditions, and is used only
in push-pull to balance out the even harmonics."
In Langford-Smith's eyes, therefore, it seems that what drove the
choice of Class AB was the ability to retain most of the power
available in Class B while reducing THD a very big chunk, without the
instability that would follow on the heels of the amount of NFB to
achieve the same task in Class B.
> > The "invention" of Class AB as a hi-
> > fidelity amp is what spurred part of a Olsen's work on perception;
> > before it wasn't known that odd harmonics are proportionately much
> > more disturbing than even harmonics. It seems to me that AB amps with
> > largish parts of their output in Class A is a relatively modern trend,
> > possibly related to ever less-sensitive speakers.
>
> I'm not sure I would agree with that, class AB amps were common even in
> the days of efficient speakers, I don't see it as "a relatively modern
> trend", if anything is a modern trend, I would think it is the return to
> "pure" class A amplifiers on the part of many audiophiles.
Sure, Class A1 amplifiers, as in SE 300B amps, are big since say the
mid-80s. But I think if you go into the history of how much of the
total power of typical Class AB amps at every period was available in
Class A, I think you will find that in the days of sensitive speakers,
when the first watt truly was everything that mattered, the Class A
benefice was quite low, a handful of watts perhaps. It is only in fact
since the 1950s that it was known to specialists that third and higher
odd harmonics are disproportionately more disturbing than the even
harmonics; you can still see the willful resistance, arising from
ignorance, to my practice of designing amps to shape the residual
harmonic artifacts so that the odd residuals are miles below the
fractional remaining second harmonic. Again, those tubes like 807s
when operated in triode were naturals for Class AB, with a naturally
beneficial harmonic spectrum; these things fell out naturally without
the obsessive thought we put into the tiniest detail these days,
bedevilling retrospective analysis.
> Regards,
>
> John Byrns
>
> --
> Surf my web pages at, http://fmamradios.com/
Of course I could be wrong. I wasn't there, I don't have twenty-twenty
hindsight, and the few amps whose histories I know about are not
exactly in the mainstream. One has to read very carefully between the
lines to understand what someone like Langford-Smith tell you when he
speaks of motives driving commercial choices rather mere engineering
facts: his milieu and assumptions were very far from ours.
Andre Jute
> Andre Jute wrote:
>
> > In the halflight dreamworld inhabited by Dougles Zero-sound, Poopie
> > Stevenson and Worthless Wiecky, SE amps would be impossible, Class A1
> > amps would be impossible, and all other classes would produce zero
> > music -- in fact all other classes would produce 100 per cent pure
> > noise by being operated at all sonic peaks at either max current and
> > zero voltage or zero current and voltage plate overvoltage. All of
> > that follows logically from Poopie's absurd redefinition of Class A as
> > a Class in which "the output device(s)never cease conducting *under
> > any signal condition*," (emphasis added). It's ludicrous.
>
> It's actually the only accurate definition.
I've already demonstrated several times that your words "under
any signal condition" make your definition grossly inaccurate. I have
already told you, Poopie Stevenson, three times that your definition
is grossly inaccurate and why. Worse, you, Poopie Stevenson, have
already admitted that your definition should be rewritten as I told
you to rewrite it, three times in all:
******
Poopie wrote:
>Do please, if you desire, change it to 'any valid signal
>condition for which the amplifer is rated'.
******
Nah, Poopie, we don't only desire it, we demand it, because this kind
of ignorance that you display so stubbornly reflects badly on all of
us.
> > Any amp can be driven out of class by excessive signal voltage.
>
> Overdriving to cut-off is merely gross abuse and a complete red herring /
> irrelevance.
Precisely. That is what I explained to you, three times in all, plus
once more from Flipper, before you finally understood and stopped
following along behind Dougles Zero-sound like a fat little lost lamb.
You are a very slow learner, Poopie.
> You really should constrain yourself to talkind about stuff you understand.
> Which would seem not to be very much going by your posting history.
Me? Come on, Poopie, I'm not the one who claimed for several days that
a Class A stage is one in which "the output device(s)never cease
conducting *under any signal condition*." You're the one who committed
that stupidity, and so many others. *You* really should constrain
yourself to talking about stuff you understand -- which would seem not
to be very much going by your posting history.
> Graham
Andre Jute
Andre Jute
wrote:
> John Byrns wrote:
> > Andre Jute <fiu...@yahoo.com> wrote:
> >
> > > Historically, the original purpose of Class AB was to annihilate the
> > > second harmonic which before made up such a very large part of the
> > > THD, while still allowing beam tubes and pentodes to give much larger
> > > power than available before.
> >
> > Andre, why was Class AB necessary to annihilate the second harmonic,
> > didn't Push Pull operation already annihilate the second harmonic
> > irrespective of the class of operation?
>
> Yes, you are right. It does.
>
> The SOLE purpose of AB is to produce larger power outputs using the same tubes.
Now this poor dumb slow learner Poopie Stevenson, an embarrassment to
everyone who comes into contact with him, claims to know more than the
RDH4! Yo, Poopie, in the RDH4 (Newnes 1997) on p 545 we find this
nugget of authoritative information by F. Langford-Smith B.Sc. B.E.
himself:
"Class AB operation indicates overbiased conditions, and is used only
in push-pull to balance out the even harmonics."
You're a fool, Poopie. You should have taken a tip from John Byrns and
asked a question rather than made a statement you cannot back up.
> The dissipation in the output tubes is very considerably lower than that in
> Class A.
You're blowing smoke out of your arse, Poopie. I'm clearly talking
about output power but you try to muddy the water with "dissipation in
the output tubes". You're not only a clown, you're a transparent
clown.
Or are you perhaps, in line with the ignorance generally displayed in
your posting history, trying to claim that more output power is
available from Class A than from Class AB? That would be a new nadir
of stupidity even for a man who just claimed that Class A devices
should conduct 360 degrees "under any signal condition".
> Graham
Andre Jute
The trouble with Poopie Stevenson is not what he doesn't know, but
what he knows for certain that isn't true. --- with apologies to Mark
Twain
Multi-grid
>
> That's a bunch of nonsense and drivel, if the cancellation were simply
> the result of "the finals are biased so that the change in
> characteristic for the opposing phases approximately cancels", then the
> amount of odd order distortion could also be changed by PP connection.
> The fact is that the even order cancellation is not dependent on the
> biasing of the tubes, beyond the requirement that the two tubes are
> identical and are both biased the same.
So then John, when one is cut off, what is cancelling?
and on this: "The fact is that the even order cancellation is not
dependent on the biasing of the tubes, beyond the requirement that
the two tubes are identical and are both biased the same.
And how are two tubes 'the same' when one is in the traditional AB
bias piont? Further, as one starts cutting off( not far from its idle
point ), how is this remotely like what is going on in the other
phase?
I'll give you a hint.....nah, you'll get it eventually.
Do try and keep your answer out of the Nonsense&Drivel category.
cheers,
Douglas
>
> Check your High School Trigonometry book to understand why the even
> harmonics cancel while the odd ones don't, it's a simple bit of math
> that doesn't depend on bias, only that the two sides of the PP circuit
> are identical.
No kidding. Where would one get these magical identical tubes?
Getting a class A amp to cancel its 2nd HD is not a trivial exercise.
I suggest you try it on your AB amps, just for kicks.
cheers,
Douglas
Multi-grid
> any rate the reason I started this sub thread was to ask if anyone more
> knowledgeable about engines than you or I knows the theory of the 8-6-4
> engine and how it was supposed to improve gasoline mileage, which as I
> remember it was what the hype said it was supposed to do?
Internal combustion efficiency is determined by the compression ratio.
High-vacuum conditions reduce the effective compression ratio. Going
to smaller displacement( through de-activating cylinders) meant
operation at higher manifold pressure, and thus higher
compression( from a given cam timing and combustion chamber geometry).
Unfortunately, you were dragging along other cylinders. There were a
few means of reducing the pumping losses, some worked better than
others. Also, the inactive cylinders were rotated in order to maintain
operating temperatures.
There's more to it, but those are the broad strokes.
cheers,
Douglas
John Byrns
Multi-grid <pen...@netscape.com> wrote:
> > That's a bunch of nonsense and drivel, if the cancellation were simply
> > the result of "the finals are biased so that the change in
> > characteristic for the opposing phases approximately cancels", then the
> > amount of odd order distortion could also be changed by PP connection.
> > The fact is that the even order cancellation is not dependent on the
> > biasing of the tubes, beyond the requirement that the two tubes are
> > identical and are both biased the same.
>
> So then John, when one is cut off, what is cancelling?
The even order spectral components of the distortion products produced
in each of the two tubes, including cutoff effects.
> and on this: "The fact is that the even order cancellation is not
> dependent on the biasing of the tubes, beyond the requirement that
> the two tubes are identical and are both biased the same.
>
> And how are two tubes 'the same' when one is in the traditional AB
> bias piont?
Both tubes must be at the same bias point, be it "traditional AB" or
whatever other bias point floats your boat.
> Further, as one starts cutting off( not far from its idle
> point ), how is this remotely like what is going on in the other
> phase?
Because both tubes are doing exactly the same thing over a complete
cycle, except out of phase.
> I'll give you a hint.....nah, you'll get it eventually.
No, I don't think I will ever get "it" unless you give me a hint.
> Do try and keep your answer out of the Nonsense&Drivel category.
Done.
> > Check your High School Trigonometry book to understand why the even
> > harmonics cancel while the odd ones don't, it's a simple bit of math
> > that doesn't depend on bias, only that the two sides of the PP circuit
> > are identical.
>
> No kidding. Where would one get these magical identical tubes?
To the extent that you can't get magical identical tubes you will have
to settle for less than complete even order distortion cancellation.
> Getting a class A amp to cancel its 2nd HD is not a trivial exercise.
It's easy enough, trivial even, to adjust the differential bias so a
single even order harmonic is canceled, even with non-identical tubes.
> I suggest you try it on your AB amps, just for kicks.
My amp operates class A.
Are you saying that getting a class A amp to cancel its 2nd HD is more
difficult than getting a class AB amp to cancel its 2nd HD, or vice
versa, or neither?
Eeyore
Andre Jute wrote:
> Eeyore <rabbitsfriend...@hotmail.com> wrote:
>
> > Andre Jute wrote:
> >
> > > In the halflight dreamworld inhabited by Dougles Zero-sound, Poopie
> > > Stevenson and Worthless Wiecky, SE amps would be impossible, Class A1
> > > amps would be impossible, and all other classes would produce zero
> > > music -- in fact all other classes would produce 100 per cent pure
> > > noise by being operated at all sonic peaks at either max current and
> > > zero voltage or zero current and voltage plate overvoltage. All of
> > > that follows logically from Poopie's absurd redefinition of Class A as
> > > a Class in which "the output device(s)never cease conducting *under
> > > any signal condition*," (emphasis added). It's ludicrous.
> >
> > It's actually the only accurate definition.
>
> I've already demonstrated several times that your words "under
> any signal condition" make your definition grossly inaccurate.
But you're an ignorant cunt and what you say is a load of bollocks.
"In a Class A circuit, the amplifying element is biased so the device is always
conducting to some extent"
http://en.wikipedia.org/wiki/Electronic_amplifier#Class_A
You're confusing cause and effect but your brain is too addled to understand the
difference.
Graham
Eeyore
Andre Jute wrote:
> Eeyore <rabbitsfriend...@hotmail.com> wrote:
>
> > You really should constrain yourself to talkind about stuff you understand.
> > Which would seem not to be very much going by your posting history.
>
> Me? Come on, Poopie, I'm not the one who claimed for several days that
> a Class A stage is one in which "the output device(s)never cease
> conducting *under any signal condition*." You're the one who committed
> that stupidity, and so many others.
And * so many others* too eh ? Ever consided we might actually be right ?
You're a FUCKING CRETIN Joot. Go back to the miserable hole you crawled out of.
Graham
Eeyore
Andre Jute wrote:
> Poopie Stevenson aka Eeyore <rabbitsfriend...@hotmail.com>
> wrote:
> > John Byrns wrote:
> > > Andre Jute <fiu...@yahoo.com> wrote:
> > >
> > > > Historically, the original purpose of Class AB was to annihilate the
> > > > second harmonic which before made up such a very large part of the
> > > > THD, while still allowing beam tubes and pentodes to give much larger
> > > > power than available before.
> > >
> > > Andre, why was Class AB necessary to annihilate the second harmonic,
> > > didn't Push Pull operation already annihilate the second harmonic
> > > irrespective of the class of operation?
> >
> > Yes, you are right. It does.
> >
> > The SOLE purpose of AB is to produce larger power outputs using the same tubes.
>
> Now this poor dumb slow learner Poopie Stevenson, an embarrassment to
> everyone who comes into contact with him, claims to know more than the
> RDH4! Yo, Poopie, in the RDH4 (Newnes 1997) on p 545 we find this
> nugget of authoritative information by F. Langford-Smith B.Sc. B.E.
> himself:
>
> "Class AB operation indicates overbiased conditions, and is used only
> in push-pull to balance out the even harmonics."
It's the push-pull that cancels those harmonics YOU UTTER CRETIN ! A Class **A**
push-pull output stage will do that too.
AB operation has NOTHING to do with distortion cancellation.
Your problem is that you don't understand what you'r reading so you quote out of
context as a result of your utter IGNORANCE.
Graham
Don Pearce
Graham, please just killfile the idiot like most of us have. His
dribbling meanderings are just as irritating at second hand as they
are when they have dropped fresh from his rear end.
d
--
Pearce Consulting
http://www.pearce.uk.com
Arny Krueger
"John Byrns" <byr...@sbcglobal.net> wrote in message
news:byrnsj-5AC26A....@newsclstr03.news.prodigy.net...
>> Which, of course, would be a 100% marketing ploy, wouldn't it? To call
>> it a 4 or a 6 by virtue of the modifications?
If not a rhetorical question, then this is a straw man argument, as the
relevant products are still called V-8s by the marketing people.
> I'm not sure it was a pure marketing ploy, especially given that I have
> seen ads for a current model car that uses this same idea today,
> unfortunately I forget what car it is, it might even be a Cadillac,
> although I would think they would be too gun shy to try it again.
AFAIK, the technology is being used in current production GM and Chrysler
cars. I have friends who drive them.
> At
> any rate the reason I started this sub thread was to ask if anyone more
> knowledgeable about engines than you or I knows the theory of the 8-6-4
> engine and how it was supposed to improve gasoline mileage, which as I
> remember it was what the hype said it was supposed to do?
A cylinder in a gas engine uses more energy if it is only partially in use
than if it is turned off. Some losses stay about the same, but other losses
are vastly reduced if you partially turn the cylinder off by means of
significantly altering the valve timing. AFAIK, the spark plug still fires
but no fuel is injected, and the amount of air that the cylinder pumps is
vastly reduced.
>> As a purpose-built 4 or 6 would be a much better solution, wouldn't
>> it?
> Better solution for what problem?
Better than operating with a very tightly closed throttle. The engines that
receive this treatment are relatively large and powerful. They are
agressively throttled back most of the time.
>> And that same purpose-built 4 or 6 could be made with the same
>> displacement, potential output HP and torque as a V8, couldn't it?
Approximately yes. Engines are built with as many cylinders as possible to
smooth the noise and vibration. They are built with as few cylinders as
possible to reduce production costs. But, varying the number of cylinders
has secondary effects, such as the torque curve, etc.
> Yes, but a 4 cylinder engine with the power of a V8 might be a little
> rough for many Cadillac buyers.
Cars with very large 4 cylinder engines have been built. One was built on
half of a V8. It was rough and noisy, not to mention being on the heavy
side. These days most larger in-line 4 cylinder engines have a balance
shaft to cancel out some of the secondary shaking motions.
>> And that would, of course, cost a pretty penny - more than a similar
>> displacement & output V8?
A really big 4 would be cheaper to build, all other things being equal.
> I would expect that a V8 would cost more than a 4 of similar
> displacement, simply based on the parts count, but what do I know.
You would be right.
> The 4 would probably require some more expensive drive train parts than
> the
> V8, at least in manual transmission applications.
I don't know about that. For one thing, we haven't said which configuration
4 this is. IME flat 4s put out a lot of low end torque for their
displacment, and require beefed-up drive trains that can handle it. In-line
4s and V6s and V8s seem to be lower on low end torque for a given
displacement and stroke/bore, and can probably get by with less beef in the
clutch, tranny, differential, and CV joints.
Arny Krueger
"Eeyore" <rabbitsfriend...@hotmail.com> wrote in message
news:471FA13A...@hotmail.com...
>
>
> Andre Jute wrote:
>
>> In the halflight dreamworld inhabited by Dougles Zero-sound, Poopie
>> Stevenson and Worthless Wiecky, SE amps would be impossible, Class A1
>> amps would be impossible, and all other classes would produce zero
>> music -- in fact all other classes would produce 100 per cent pure
>> noise by being operated at all sonic peaks at either max current and
>> zero voltage or zero current and voltage plate overvoltage. All of
>> that follows logically from Poopie's absurd redefinition of Class A as
>> a Class in which "the output device(s)never cease conducting *under
>> any signal condition*," (emphasis added). It's ludicrous.
>
> It's actually the only accurate definition.
Agreed.
>> Any amp can be driven out of class by excessive signal voltage.
> Overdriving to cut-off is merely gross abuse and a complete red herring /
> irrelevance.
Agreed. Jute seems to be addicted to excluded-middle arguments. Kick out
those and the straw men, and he's hardly have anything to say. ;-)
> You really should constrain yourself to talkind about stuff you
> understand.
It would save a lot of bandwidth.
> Which would seem not to be very much going by your posting history.
Jute is mostly about hyperbole. In real life he makes Walter Mitty look
like a world-class adventurer. ;-)
Don Pearce
wrote:
>A cylinder in a gas engine uses more energy if it is only partially in use
>than if it is turned off. Some losses stay about the same, but other losses
>are vastly reduced if you partially turn the cylinder off by means of
>significantly altering the valve timing. AFAIK, the spark plug still fires
>but no fuel is injected, and the amount of air that the cylinder pumps is
>vastly reduced.
In the huge diesels that routinely turn off multiple cylinders, the
valve gear is uncoupled so the valves remain closed. That way no air
is pumped and the losses drop to negligible levels. You really don't
want to be shifting air, even if there is no combustion, if economy is
your objective.
Don Pearce
wrote:
>
>"Eeyore" <rabbitsfriend...@hotmail.com> wrote in message
>news:471FA13A...@hotmail.com...
>>
>>
>> Andre Jute wrote:
>>
>>> In the halflight dreamworld inhabited by Dougles Zero-sound, Poopie
>>> Stevenson and Worthless Wiecky, SE amps would be impossible, Class A1
>>> amps would be impossible, and all other classes would produce zero
>>> music -- in fact all other classes would produce 100 per cent pure
>>> noise by being operated at all sonic peaks at either max current and
>>> zero voltage or zero current and voltage plate overvoltage. All of
>>> that follows logically from Poopie's absurd redefinition of Class A as
>>> a Class in which "the output device(s)never cease conducting *under
>>> any signal condition*," (emphasis added). It's ludicrous.
>>
>> It's actually the only accurate definition.
>
>Agreed.
>
>>> Any amp can be driven out of class by excessive signal voltage.
>
>> Overdriving to cut-off is merely gross abuse and a complete red herring /
>> irrelevance.
>
>Agreed. Jute seems to be addicted to excluded-middle arguments. Kick out
>those and the straw men, and he's hardly have anything to say. ;-)
>
Can you overdrive a class A amp to cutoff? In my experience what
happens when you overdrive a class A amp is that one device saturates,
and the other sticks with its normal bias condition. There is no
circumstance in which I have ever managed to put a class A amplifier
output device into cutoff.
Arny Krueger
"Don Pearce" <nos...@nospam.com> wrote in message
news:47236219....@news.plus.net...
> On Thu, 25 Oct 2007 10:26:32 +0100, Eeyore
> <rabbitsfriend...@hotmail.com> wrote:
>
>>
>>
>>Andre Jute wrote:
>>
>>> Poopie Stevenson aka Eeyore <rabbitsfriend...@hotmail.com>
>>> wrote:
>>> > John Byrns wrote:
>>> > > Andre Jute <fiu...@yahoo.com> wrote:
>>> > >
>>> > > > Historically, the original purpose of Class AB was to annihilate
>>> > > > the
>>> > > > second harmonic which before made up such a very large part of the
>>> > > > THD, while still allowing beam tubes and pentodes to give much
>>> > > > larger
>>> > > > power than available before.
>>> > >
>>> > > Andre, why was Class AB necessary to annihilate the second harmonic,
>>> > > didn't Push Pull operation already annihilate the second harmonic
>>> > > irrespective of the class of operation?
>>> >
>>> > Yes, you are right. It does.
>>> >
>>> > The SOLE purpose of AB is to produce larger power outputs using the
>>> > same tubes.
Or bits of silicon, or whatever amplification device is being used.
>>> Now this poor dumb slow learner Poopie Stevenson, an embarrassment to
>>> everyone who comes into contact with him, claims to know more than the
>>> RDH4! Yo, Poopie, in the RDH4 (Newnes 1997) on p 545 we find this
>>> nugget of authoritative information by F. Langford-Smith B.Sc. B.E.
>>> himself:
>>> "Class AB operation indicates overbiased conditions, and is used only
>>> in push-pull to balance out the even harmonics."
No such thing in the RDH4 at hand.
>>It's the push-pull that cancels those harmonics YOU UTTER CRETIN ! A Class
>>**A**
>>push-pull output stage will do that too.
Agreed.
>>AB operation has NOTHING to do with distortion cancellation.
Agreed.
>>Your problem is that you don't understand what you'r reading so you quote
>>out of
>>context as a result of your utter IGNORANCE.
Seems like Jute has his own private translation of the RDH4 that adds errors
to what the original authors wrote.
> Graham, please just killfile the idiot like most of us have. His
> dribbling meanderings are just as irritating at second hand as they
> are when they have dropped fresh from his rear end.
The guy who manipulates the Jute sockpuppet is an attention-hound, pure and
simple.
Arny Krueger
> On Thu, 25 Oct 2007 05:56:37 -0400, "Arny Krueger" <ar...@hotpop.com>
> wrote:
>
>>A cylinder in a gas engine uses more energy if it is only partially in use
>>than if it is turned off. Some losses stay about the same, but other
>>losses
>>are vastly reduced if you partially turn the cylinder off by means of
>>significantly altering the valve timing. AFAIK, the spark plug still fires
>>but no fuel is injected, and the amount of air that the cylinder pumps is
>>vastly reduced.
>
> In the huge diesels that routinely turn off multiple cylinders, the
> valve gear is uncoupled so the valves remain closed.
Thats about the same as what they do in the cars I mentioned.
>That way no air
> is pumped and the losses drop to negligible levels.
Agreed.
> You really don't
> want to be shifting air, even if there is no combustion, if economy is
> your objective.
That seems to be how the technology works. I am informed by my friends who
have cars that implement this strategy, that there are consistent and
significant real-world fuel economy gains, as measured by modern car
computers that display dynamic fuel economy measures.
Patrick Turner
Andre Jute wrote:
>
> On Oct 24, 6:57 am, flipper <flip...@fish.net> wrote:
> > On Wed, 24 Oct 2007 13:44:13 +0100, Eeyore
> >
> >
> >
> > <rabbitsfriendsandrelati...@hotmail.com> wrote:
> >
> > >Patrick Turner wrote:
> >
> > >> Eeyore wrote:
> > >> > Multi-grid wrote:
> > >> > > maxhifi <n...@spam.com> wrote:
> >
> > >> > > > Stating that "the amplifier is Class A until XXX watts", really, is
> > >> > > > telling you how hot the tubes are biased relative to the two extremes of
> > >> > > > pure class A (full dissapation), and pure class (cut off).- Hide quoted text -
> >
> > >> > > Class A has nothing to do with dissipation either. Just because some
> > >> > > marketing group noticed that class A means something good, does not
> > >> > > make it right either. Just because it seems to make sense is no reason
> > >> > > to bastardize the definition. Find some other way to describe it.
> >
> > >> > The definition of Class A is very simple. It requires that the output device(s)
> > >> > never cease conducting under any signal condition.
> >
> > >> It means slightly more than this because tubes don't cut off as sharply
> > >> as other devices.
> >
> > >I see what you're saying but I do believe that the definition is unchanged. Obviously
> > >avoiding any region of significant non-linearity is preferable but that in its own right
> > >doesn't change the definition.
> >
> > People are talking semantically past each other with some speaking of
> > the definition of the 'amplifier' class while others are speaking of
> > it's behavior under a restricted set of operating conditions; and it
> > is useful to observe that under an appropriately restricted set of
> > conditions the output tubes conduct 360 degrees as in 'Class A'
> > operation.
>
> "Useful", indeed, Flipper. Thanks. But I would go further and say that
> the signal and dissipation restriction is part of the definition, as
> you go on to imply:
>
> > For example, if maximum power, or efficiency, were the primary concern
> > then one might bias more to the 'B' side of the equation while if
> > fidelity were the primary concern one might bias more to the 'A'.
>
> Precisely. Both Class A operation and Class B operation are inherent
> in the nomenclature and definition and their relative importance is
> clearly intended to be in the designer's discretion.
>
> Historically, the original purpose of Class AB was to annihilate the
> second harmonic which before made up such a very large part of the
> THD, while still allowing beam tubes and pentodes to give much larger
> power than available before. The "invention" of Class AB as a hi-
> fidelity amp is what spurred part of a Olsen's work on perception;
> before it wasn't known that odd harmonics are proportionately much
> more disturbing than even harmonics. It seems to me that AB amps with
> largish parts of their output in Class A is a relatively modern trend,
> possibly related to ever less-sensitive speakers.
He he, No, The largish % of class A power in an "AB" amp is a very very
rare trend these days.
I cannot think of a single PP amp which has a large % of class A power.
ARC and CJ and most others are locked into a stupid desperate war of
watts, where they
try to extract a maxima of class AB watts and to hell with class A, and
reliability.
Who is going to buy a class AB amp with 2 x 6550 per channel that puts
out a "parsimonious 50 watts"
when the guy down the road is making a similar amp which puts out 75
watts?
Hell, may as well try for 100 watts.
The Chinese meanwhile are dumping absolute crap onto the market which
falls apart or burns out sooner rather than later
and distracts buyers from spending on ARC and CJ who of course have
prices which are 15dB higher than the Chinese amps.
To try to snare sales though, the big US brands try to extract more
power, its like they
can't bare to be seen to make 40 watt amps with a pair of 6550 and then
be seen to charge the 15dB more.
What the big makers do, ARC, CJ and many others around the globe is just
raise the B+, and lower idle current,
and then lower the RLa-a and presto, you have a raw PA amp around which
you run about
12dB max of GNFB, and call it hi-fi, but your lucky if there is 5 watts
of class A before the amp lurches into
class AB for the majority of the power ability of 75 watts which BTW
will NEVER get used.
Amp manufacture has, like 1,001 other products become a marketting
exercize,
not any thing else. Certianly not an exercize in providing maximal
fidelity
with a minimum of NFB.
>
> > One might also observe that's likely why it's called Class AB and not
> > Class <insert unique letter>.
>
> There is in fact a class between Class A and Class AB with a unique
> description: "Limiting Class A1", which is set up so that the
> crossover happens when one valve just reaches current cutoff and the
> other simultaneously reaches zero bias. It makes for an amazingly
> smooth sound but it is a bitch to set up and keep tuned if you want to
> keep your circuits simple. I was therefore rather interested in what
> Patrick said elsewhere in this thread (in more general sense rather
> than specifically about LImitiing Class A1) about within 10 per cent
> of conduction angle being imperceptible...
Limited class A is the correct term, not limiting, which can mean
something else.
All PP class AB amps are capable of producing class A power only and
never moving into class AB.
And I meant what I said about defining the class A. Class A in a PP amp
is where the anode current is *always* at leasst above 10% of the idle
current.
So where you have 50mA of idle current in each of the PP tubes, and an
Ia swing of +/- 45mA,
each tube is working in PURE class A, and thus the pair are ALSO said to
be working in pure class A.
Suppose you have a pair of tubes, fixed bias, B+ = +500V, and a swing of
+/- 350Vpk
on each tube. There is 700Vpk a-a, = 500Vrms.
Let us say the Ia change at each anode = + or - 45mApk, then the RL seen
at each anode
while working in pure class A = 350V / 0.045A = 7.78k.
Effectively, the OPT places these loads in series, and you have a load
RL a-a = 2 x 7.78k, or 15.6k.
With 500vrms across 15.6k, you get 16 watts of pure class A.
The idle pda for each tube = 500V x 0.05A = 25 watts, so for 2 tubes its
50 watts.
Efficiency maximum = 16 / 50 = 32%.
We would be describing approximately the outcome with a pair of pure
class A KT88 in triode.
So what happens when we use a 5k load on the same amp?
The same idle current flows, and the same range of Ia variation 0f +/-
45mA will define the
class A **current** swing, ( where the **current** wave THD < 5% and
mainly all 2H ).
So the class A load on each tube = 1/2 x 5k = 2.5k, so the maximum class
A V swing at each anode
= 2,500ohms x 0.045A pk = 112.5Vpk = 225pk from anode to anode, or
159vrms across 5k,
giving 5 watts of class A.
But the load value allows for a much larger increase in Ia than the 50mA
of maximum decrease in Ia.
This also means that once the Ia travels below 10% of the idle value,
the gm of the tube cutting off
has diminished to such a low value the other tube turning on harder is
providing virtually all the Ichange x Vchange
across the available load, and is the only device coupled through only
1/2 the OPT primary
to the load, so the RL seen by this tube turning on hard has reduced to
1/2 its class A load,
or 1/4 of the nominal RL a-a, and in this case its 1.25k.
The load is the same as that for a class B amp.
Load lines will describe it all far better at my website. But you would
find that triodes
in AB with Ea = 500V, and load of 5ka-a can make a peak Emin = 220V, so
swing = 500-220 = 280V,
and at this point peak Ia = 220mA approx on each output tube, and this
operation is at the limit
of operation without being hindered by grid current.
So pk a-a sw = 560V pk = 396vrms, and this means you get 31 watts of
class AB power into 5k.
5 watts of pure class A is possible, then the operation ***gradually***
changes from
impure class A to AB, where one tube cuts off gradually, and the other
tube turning on reaches
a peak current several times the idle value.
if the current waves in each tube are examined, with a 5k load the waves
are seen to have about 5%
mainly 2H when making 5 watts into 5k, but at 31 watts, the current THD
becomes
over 20% with lots of harmonics.
Most don't reach our ears because of the complementary action of the two
tubes.
Pentodes and beam tetrode amps have less gradual change than triodes
when passing from class A to class AB,
and in fact generate far more dirty sounding "switching" harmonics
higher than 2&3H in what is called the "switching zone"
or "crossover region".
McIntosh became renowned for producing 50 watts from a pair of 6L6
running
them in low bias current class AB, and applying a total huge amount of
local and global
NFB to get the Rout and THD/IMD low.
ARC use 16 x 6550 in their reference 600 amps to make 600 watts.
This means there is 75 watts coming from each pair of PP output 6550.
Not much class A power though.
I have just completely re-engineered and re-wired an ARC VT100, made in
1996.
It has 4 x 6550 per channel.
I found that when there was 8 ohms connected to the 0-8 outlet,
you'd get about 125watts of AB power, but very little class A because
the tubes were being pushed hard into class AB1.
8 ohms was the load where maximum PO is available.
I found that using an 8 ohm load connected to the 0-4ohm outlet
gave less maximum PO, about 75 watts but a much higher % of class A po
before class AB PO begins.
The speakers I have to test this amp for any remaining bugs have 8 ohm
woofers for 20Hz to 250Hz,
and a pair of 6 ohm SEAS midranges in series for 250Hz to 3.2kHz and a
dome 6 ohm SEAS tweeter
for above 3.2kHz.
The speaker Z is thus well above 8 ohms in the main power band for
music,
and when cranked loud, the amp's new green-red LEDs which indicate Idc
at the cathodes do not
change from the correct pale green to red.
There is plenty of class A power AND GREAT NATURAL FIDELITY available.
Some folks would insist in using "4" ohm speakers with dips in the main
power band to 2 ohms,
and connect to the 0-4 ohm outlet **which really should be labelled
0-8**.
The 0-8 outlet should be re-laelled 0-16 ohms.
The use of speakers with Z = average 3 ohms instead of 10 ohms like I
have means
that the THD/IMD will be approximately 3 times as high for the same PO
as with 10ohms, class A power is reduced to near nothing,
and the damping factor is hopeless.
Class AB PP amps have a varying Rout which is lowest while
the amp works in class A, but which doubles when in class AB at extremes
of wave points. This unfixed Rout translates to compression,
massive 3H, and lots more IMD than while working in class A.
Anyway, the quad of 6550 while working in class A with a 10ohm load
connected
across the mis-labelled 0-4 ohm outlet do sound VERY well.
Those wanting a schematic of what have done may ask as I have a .gif
available.
Its much simpler than the original, and I won't beak ARC rules by
handing out free copies of their
abominable concoctious junk.
The reformed ARC VT100 can make 23Vrms into 8 ohms at its 0-4 ohm
outlet, = 66 watts,
or about 24Vrms into 10 ohms = 57 watts, which is completely plenty!
The 0-8 ohm outlet should ***never be used*** unless you have genuine
16+ ohm speakers,
or perhaps ESL where the Z is high below 1kHhz down to 100Hz, and you
simply need a large voltage drive.
One may always have a high Z midrange ESL across the 0-8 ohm outlet, and
a lowZ woofer
across the 0-4 ohm outlet.
The other config available is the 4-8 connection.
This amount of never-spoken-about-section-of-winding
is equal to 0.293 x the whole secondary winding turns, which is a
theoretical match for 16 ohms, but should have been for 32 ohms.
The 4-8 connection gives a match to 1.37 ohms, if we considered the two
labelled
4 and 8 as right.
In fact, the VT100 would give superlative fidelity into 2.7 ohms
if a speaker of 2.7+ ohms was connected between the 8 and 4 output
posts.
I have set up the VT100 so it has separate bias adjust pots for each
tube,
and Ia+Ig2 at idle = 39mA measured at the cathode. VT100 is a UL amp
with OPT with ct speaker secondary which is optimistically a match for
16 ohms,
and each end applies some local CFB to the output tubes.
I have Ea at +430V, so Pd at idle for each 6550 = 17 watts only.
One can only barely keep a hand on the mesh cover over the tubes even
with such a low Pd at idle.
I sure don't need to run the 6550 any hotter than they are now.
The amp may be played very loud, and music does not unbias the amp
badly.
The total Pd = 67 watts, and if UL class A efficiency max = 45%,
then maximum possible class A from this amp = 30 watts, AND THIS IS
PLENTY!!!
I have also fixed an ARC Reference One preamp to use with the VT100.
One of its EI-6922 had gone noisy.
Its complicated circuit has been left alone except for lifting the OV
rail from the case
and re-connecting via 22 ohms.
The VT100 had a true horror for a PSU and after fitting a CLC B+ filter
and re-locating
earth paths, I finally got hum&noises to be less than 1mV with preamp
gain at max with
open cd input. The ARC Reference one preamp is a fully balanced design
except that the balanced output
isn't from a floating secondary of a transformer. It should be, but
ain't.
Gain max is 12dB, and because there are 8 x 1/2 6922 triodes used in
each channel, with an easily possible open loop
gain of 1,000 at least, I would suppose that the level of global NFB
used around
the totally balanced LTP type stages amounts to about
40dB at least.
Its bandwidth = 1Hz to 680kHz, and noise is low, and it is a superbly
measuring preamp.
But I would get similar sound using 2 triodes instead of 8 in a line
stage, and have no need for balanced at all.
The ARC preamp does seem to be sonically neutral as one would expect
from a totally pure class A amp with a shirtload and bootful of NFB.
I am amused at those who would say that changeing from say Sovtek
6DJ8/6922
will change the sound from say Siemans NOS 6DJ8. I would always suggest
that the high amount of NFB
must blind the listener to sonic variations, since any artifact or sonic
signature is cancelled away by the NFB action.
For a lot more about class A and AB in power amps, go to the
educational/diy pages at my website.
http://www.turneraudio.com.au
Patrick Turner.
Patrick Turner
John Byrns wrote:
>
> In article <1193239797.1...@k35g2000prh.googlegroups.com>,
> Andre Jute <fiu...@yahoo.com> wrote:
>
> > Historically, the original purpose of Class AB was to annihilate the
> > second harmonic which before made up such a very large part of the
> > THD, while still allowing beam tubes and pentodes to give much larger
> > power than available before.
>
> Andre, why was Class AB necessary to annihilate the second harmonic,
> didn't Push Pull operation already annihilate the second harmonic
> irrespective of the class of operation?
Class AB was found to be more efficient and cheaper per watt to produce,
and give better sonic performance than the SE amps of 1935.
Once anyone needed more than 3 watts, PP was considered,
and the bonus was to banish high THD/IMD of the SE amps of the day.
The SE radio amps using a lone 6V6 in beam tetrode mode with no NFB were
often used,
and had mainly 2H, but many OTHER H, and sounded lousy over a whisperish
level.
HOWEVER, in the misplaced zeal to banish 2H and settle for the clean PP
sound, especially
when you had a pair of output 2A3, designers would labour away to force
an input triode to feed and IST to
drive the PP outputs with a two phase secondary.
SUN amps are a classic example.
Typical primary voltage needed at the 1:2 IST = 50Vrms.
So the bloomin input driver tube was making lots of 2H and there was NO
net betterment in the sonics except
that because the power ceiling was slightly higher.
More thoughtful PP amps were designed in the late 40s by leak, Quad,
Radford etc, where
ALL distortion was considered bad, and where the driver stages were
designed to produce far less THD/IMD
than the output stage.
The Williamson is a classic example.
It can be used with 300B in the output, and NFB needn't be used, and
THD/IMD will remain low enough,
and the 28 watts AB1 will be enough for most folks even now with
insensitive speakers.
With sensitive speakers of the 50s, the 28 watts of AB triode power
was the equivalent of having 112 watts today on average.
But very very fine SE amps can be built, and the 2H is low,
along with other H, and not much NFB need be used.
Patrick Turner.
>
> > The "invention" of Class AB as a hi-
> > fidelity amp is what spurred part of a Olsen's work on perception;
> > before it wasn't known that odd harmonics are proportionately much
> > more disturbing than even harmonics. It seems to me that AB amps with
> > largish parts of their output in Class A is a relatively modern trend,
> > possibly related to ever less-sensitive speakers.
>
> I'm not sure I would agree with that, class AB amps were common even in
> the days of efficient speakers, I don't see it as "a relatively modern
> trend", if anything is a modern trend, I would think it is the return to
> "pure" class A amplifiers on the part of many audiophiles.
>
Patrick Turner
Multi-grid wrote:
>
> On Oct 24, 6:29 pm, Andre Jute <fiul...@yahoo.com> wrote:
>
> >
> > Historically, the original purpose of Class AB was to annihilate the
> > second harmonic which before made up such a very large part of the
> > THD, while still allowing beam tubes and pentodes to give much larger
> > power than available before. .
> >
> > >
>
> >
> >
> >
> > - Show quoted text -
>
> Well Andre, you've stepped in it this time...:) AB operation cannot
> effectively cancell *ANYTHING*.
Cancelation of even order harmonics occurs in amps working in class AB
during that part of the wave forms which are in class A, ie, the bits
either side
of the zero crossing.
But once each tube moves into cut off, nothing is cancelled.
The two non linear current waves in the tubes of the AB pair
are summed, and the VOLTAGE total is substantially linear, with a small
fraction of the
THD of each tube's current wave.
Its magic, but it works for most ppl.
>
> Odd sums anyway.
Depends on the phase of the harmonics relative to fundemental.
Its possble to have the 3H of the driver stage acting like compression,
and the 3H of the low bias current output stage with 3H acting like
expansion,
and then there is the transformer 3H etc.....
Nothing is general, generic, or simply explained for all occasions, he,
he.
> Not second HD( or the even of any order ) because each phase is biased
> where the characteristics are changing too rapidly with plate current.
> This is the rest of the Class A definition that is implied, the finals
> are biased so that the change in characteristic for the opposing
> phases approximately cancells( and thus the even HD ). It is why the
> AB amp can't be labled A while both phases of the finals are
> conducting( or that that single definition is not enough to describe
> Class A ).
Ah, but all AB amps start off with at least a bit of pure class A before
beginning to work in AB.
Even transistor amps with miniscule bias currents, and acting very close
to pure class B amps.
There is always some little bit of class A power where the I swing +/-
is less than the idle current.
That's class A.
Its not the most wonderful class A, but its still class A.
>
> The x power in A, and XXX power in AB is just serving notice that
> marketing had its way with the ad copy.
>
> AB was an obvious means of minimizing cross-over distortion and
> maximizing power.
Indeed it was, and still is.
It works just as well for directly heated triodes
> with no NFB as it does for pentodes like the KT88 running a lot of
> it...:)
> cheers,
> Douglas
Purists don't like impurity like the Pope don't read Penthouse.
Class AB triodes are NOT much used because the 3H is considerable,
and for a given % of 3H, its 9/4 times worse than the same % of 2H.
Some say its 27/8 times worse.
But its never the THD itself that bothers, because music is mainly all
harmonic which are related
except for some notes which ain't related and the transients; drum beats
etcs.
Its the resulting IMD that really grates, and the sum and difference
frequencies produced
when a zillion F are in the amp at the same time dynamically adds up to
unwanted grunge
as background noise better abandoned if possible, except abandoning 2H,
3H etc
is not so easy as dropping off an unwanted child at the orphanage.
You gotta cancel it out, not so easy, or feedback it, or prevent it
happening in the first place by using all class A to cover the whole
dynamic range.
So many purists will go for an SE triode operating right in the middle
of its most linear
curve, then use only a small part of the curve, which is nearly
straight,
so the music sounds fine. Horns and SET were made for each other.
I would say that the IMD products produced by an amp with low 2H is
probably
nowhere near as objectionable than the same amount of IMD products
made by a PP amp.
A PP amp which is into AB transition during average levels isn't any
better sounding than the SET...
Patrick Turner.
Patrick Turner
Multi-grid wrote:
>
> >
> > That's a bunch of nonsense and drivel, if the cancellation were simply
> > the result of "the finals are biased so that the change in
> > characteristic for the opposing phases approximately cancels", then the
> > amount of odd order distortion could also be changed by PP connection.
> > The fact is that the even order cancellation is not dependent on the
> > biasing of the tubes, beyond the requirement that the two tubes are
> > identical and are both biased the same.
>
> So then John, when one is cut off, what is cancelling?
Look at the current wave in each tube. In AB or B the current wave has
SEVERE distortion spectra.
But the voltage across the WHOLE PP OPT primary is largely free of the
horrendous THD in each tubes current wave.
So its THD reduction by complementary action.
Its like two men sawing a log with a long bush saw, with one man at each
end either pulling or pushing the saw
all the way on each stroke. This is class A, and the differences in
applied forces by each man tend to cancel
and a linear saw action results.
In class AB, each man pulls the saw about 1/2 way across the stroke then
lets go,
and the other guy grabs his saw handle and pulls the saw back the other
way.
Each man only mainly pulls the saw in turn, and applied force is jerky,
and frankly,
a difficult way to work; the Union will be down soon to have a go at the
boss who told
the men to saw the log that way.
But in electronics, we can switch things on and off with absolute ease,
and there is no
Triode Union to make a boss's life a misery.
>
> and on this: "The fact is that the even order cancellation is not
> dependent on the biasing of the tubes, beyond the requirement that
> the two tubes are identical and are both biased the same.
>
> And how are two tubes 'the same' when one is in the traditional AB
> bias piont? Further, as one starts cutting off( not far from its idle
> point ), how is this remotely like what is going on in the other
> phase?
>
> I'll give you a hint.....nah, you'll get it eventually.
>
> Do try and keep your answer out of the Nonsense&Drivel category.
> cheers,
> Douglas
We all get it in the end....
> > Check your High School Trigonometry book to understand why the even
> > harmonics cancel while the odd ones don't, it's a simple bit of math
> > that doesn't depend on bias, only that the two sides of the PP circuit
> > are identical.
>
> No kidding. Where would one get these magical identical tubes?
>
> Getting a class A amp to cancel its 2nd HD is not a trivial exercise.
It mainly IS a trivial exercize and was invented about 2 days after the
first triode was made.
Any two tubes are never identical, but are often within 90% equal to
each other.
Therfore the 2H cancelation in pure class A PP is so substantial that
90%
of the 2H of either tube is cancelled away leaving far far less than if
the two tubes were
used in SE & parallel for the same class A power.
> I suggest you try it on your AB amps, just for kicks.
> cheers,
> Douglas
Trying to make the driver stage make distortions that will cancel the
output stage's PP distortions
is extremely difficult to achieve, and nobody sets out to do it. I tried
it, I failed.
Trouble is that PP output tube distortions change in amplitude and
perhaps phase and spectra
with the dynamic changes in loads connected. Speakers are not lile a
simple one value resistance.
One can manage to more easily exploit 2H cancelling phenomena in SE amps
between SE driver and SE output tube.
PP amp makers all sensibly try to make the driver linear, and output
stage linear,
and then not have to apply too much NFB to cancel the little amount of
mainly 3H distortion..
Some think this is BS, and build a class B thing with lots of THD/IMD
without any NFB.
Then they apply lots more NFB than the fella using mainly all class A in
his output stage.
The unruly class B amp with a shirtload of NFB in the output stage
McIntosh, emitter follower etc,
and a bootfull of global NFB has become the natural choice of
profit hungry amp makers. If you hunger for best music, you must spend
more
for the inefficiency costs of class A.
The staus quo among all amps is 95% AB with rough working AB / near B
devices switching with lots of NFB.
5% are either mainly class A, or AB tube amps, or the new PWM amps with
whatever correction facilities thay can muster.
In 20 years time, all the SS AB amps will have become extinct like
dinosaurs.
The PWM amps can sound as good as generic low bias SS amps and be far
more efficient and far cheaper and lighter/smaller.
Tubes will remain if the Greenhouse Police are not too zealous, and they
will hold sway amoung a
small minority of listeners actually willing to put their money on the
sound,
rather like there will always be someone who likes sailing yachts around
the bay,
rather than drive around the bay in a stink boat.
Patrick Turner.
Patrick Turner
But it does. There is partial cancelation of 2H currents up until cut
off in one device,
and in each wave of signal voltage.
However, despite the very non linear **currents** in each PP device when
in AB,
the net voltage & current when summed in the load is substantially
linear.
The equivalent circuit of a PP pair is that of two non linear current
generators in series with each end of the
RLa-a. The summed current in Rla-a is linear.
But you can also have PP action and class B where the devices are in
parallel and working on a common load.
There us more than one way to set up devices in PP...
Patrick Turner.
Eeyore
Patrick Turner wrote:
> Eeyore wrote:
> > Andre Jute wrote:
> > > Poopie Stevenson aka Eeyore wrote:
> > > > John Byrns wrote:
> > > > > Andre Jute <fiu...@yahoo.com> wrote:
> > > > >
> > > > > > Historically, the original purpose of Class AB was to annihilate the
> > > > > > second harmonic which before made up such a very large part of the
> > > > > > THD, while still allowing beam tubes and pentodes to give much larger
> > > > > > power than available before.
> > > > >
> > > > > Andre, why was Class AB necessary to annihilate the second harmonic,
> > > > > didn't Push Pull operation already annihilate the second harmonic
> > > > > irrespective of the class of operation?
> > > >
> > > > Yes, you are right. It does.
> > > >
> > > > The SOLE purpose of AB is to produce larger power outputs using the same tubes.
> > >
> > > Now this poor dumb slow learner Poopie Stevenson, an embarrassment to
> > > everyone who comes into contact with him, claims to know more than the
> > > RDH4! Yo, Poopie, in the RDH4 (Newnes 1997) on p 545 we find this
> > > nugget of authoritative information by F. Langford-Smith B.Sc. B.E.
> > > himself:
> > >
> > > "Class AB operation indicates overbiased conditions, and is used only
> > > in push-pull to balance out the even harmonics."
> >
> > It's the push-pull that cancels those harmonics YOU UTTER CRETIN ! A Class **A**
> > push-pull output stage will do that too.
> >
> > AB operation has NOTHING to do with distortion cancellation.
>
> But it does.
ONLY because AB working is by design push-pull. The same thing happens in long-tailed
pairs. the distortion cancellation is NOTHING whatever to do with AB operation.
Graham
John Byrns
nos...@nospam.com (Don Pearce) wrote:
> Can you overdrive a class A amp to cutoff?
Yes, it is painfully easy.
> In my experience what
> happens when you overdrive a class A amp is that one device saturates,
> and the other sticks with its normal bias condition.
No, the coupling capacitor charges up as a result of grid current
shifting the bias point so that cutoff becomes even easier.
> There is no
> circumstance in which I have ever managed to put a class A amplifier
> output device into cutoff.
You haven't tried very hard then.
John Byrns
Patrick Turner <in...@turneraudio.com.au> wrote:
> Cancelation of even order harmonics occurs in amps working in class AB
> during that part of the wave forms which are in class A, ie, the bits
> either side
> of the zero crossing.
>
> But once each tube moves into cut off, nothing is cancelled.
Patrick, I'm surprised to hear you say this. What are you trying to
tell us, that the even order harmonics are only cancelled during those
parts of the cycle when both tubes are conducting, but that the even
order distortion components reappear during those parts of the cycle
when only one tube is conducting? If you actually believe that you
should go back to the books and study the theory of harmonic distortion
more carefully. I hope you didn't get this notion from the RDH4, I
haven't read the RDH4's harmonic distortion explanation, but if this is
what it says I have just lost any respect I had for the book. In a
perfectly balanced PP amplifier the even order harmonic distortion is
completely cancelled even when the tubes are cut off for parts of the
cycle. It sounds like you have become one of Multi-grid's sock-puppets.
> The two non linear current waves in the tubes of the AB pair
> are summed, and the VOLTAGE total is substantially linear, with a small
> fraction of the
> THD of each tube's current wave.
And that small fraction is very small indeed, approaching zero to be
precise, for the even harmonics.
> Its magic, but it works for most ppl.
It's not magic, it's just math.
Eeyore
John Byrns wrote:
> Patrick Turner <in...@turneraudio.com.au> wrote:
>
> > Cancelation of even order harmonics occurs in amps working in class AB
> > during that part of the wave forms which are in class A, ie, the bits
> > either side of the zero crossing.
> >
> > But once each tube moves into cut off, nothing is cancelled.
>
> Patrick, I'm surprised to hear you say this. What are you trying to
> tell us, that the even order harmonics are only cancelled during those
> parts of the cycle when both tubes are conducting, but that the even
> order distortion components reappear during those parts of the cycle
> when only one tube is conducting? If you actually believe that you
> should go back to the books and study the theory of harmonic distortion
> more carefully. I hope you didn't get this notion from the RDH4, I
> haven't read the RDH4's harmonic distortion explanation, but if this is
> what it says I have just lost any respect I had for the book. In a
> perfectly balanced PP amplifier the even order harmonic distortion is
> completely cancelled even when the tubes are cut off for parts of the
> cycle.
I'd love to know how that happens. There's no cancellation of ANYTHING once one
side has ceased conducting !
Graham
Don Pearce
Because if you add an even harmonic to a signal, you have to make it
asymmetrical. You always get a peak coinciding with a trough on one
half cycle, followed by a peak coinciding with a peak on the next. If
you modify the signal to remove any asymmetry, you must by definition
remove the even harmonics.
Arny Krueger
"Patrick Turner" <in...@turneraudio.com.au> wrote in message
news:4720942B...@turneraudio.com.au...
> In class AB, each man pulls the saw about 1/2 way across the stroke then
> lets go,
> and the other guy grabs his saw handle and pulls the saw back the other
> way.
> Each man only mainly pulls the saw in turn, and applied force is jerky,
> and frankly,
> a difficult way to work; the Union will be down soon to have a go at the
> boss who told
> the men to saw the log that way.
So speaks someone who obviously has no experience cutting wood with a
cross-cut saw. You can pull on a saw, but pushing on it can easily cause it
to bend and bind. When 2 men use a cross-cut saw, each man pulls far more
than he pushes.
Class AB verging on pure class B is the preferred mode of operation for a
cross-cut saw.
Arny Krueger
Actually, there is cancellation regardless of whether one side has ceased
conducting or not, because the cancellation comes from the fact that the
transfer functions of the two sides are identical but opposite.
During the portion of the wave where both sides conduct, there may be
cancellation of odd order distortion.
In school I was taught the law of half-wave symmetry. Any wave, no matter
how distorted, that has matching halves has no even-order distortion.
A wave that is composed of one half of any kind and the other half is zero,
has only even-order distortion.
Arny Krueger
Don Pearce
wrote:
>In article <47256a39....@news.plus.net>,
> nos...@nospam.com (Don Pearce) wrote:
>
>> Can you overdrive a class A amp to cutoff?
>
>Yes, it is painfully easy.
>
>> In my experience what
>> happens when you overdrive a class A amp is that one device saturates,
>> and the other sticks with its normal bias condition.
>
>No, the coupling capacitor charges up as a result of grid current
>shifting the bias point so that cutoff becomes even easier.
>
>> There is no
>> circumstance in which I have ever managed to put a class A amplifier
>> output device into cutoff.
>
>You haven't tried very hard then.
>
The designs I have used must have been better matched in drive level
between the driver and output stages. They tended to limit almost
simultaneously so that the drive level to the output stage did not go
on rising as the input signal increased, just squared off. As I say, I
never saw an output valve go into cutoff.
John Byrns
nos...@nospam.com (Don Pearce) wrote:
Finally a man who understands the theory!
John Byrns
"Arny Krueger" <ar...@hotpop.com> wrote:
Are you sure about this? I guess I will have to do some homework.
> In school I was taught the law of half-wave symmetry. Any wave, no matter
> how distorted, that has matching halves has no even-order distortion.
Aren't there two symmetry laws, I can never remember the second one, or
is it the first?
> A wave that is composed of one half of any kind and the other half is zero,
> has only even-order distortion.
Could you say that again please?
John Byrns
"Arny Krueger" <ar...@hotpop.com> wrote:
I was going to call him on that, maybe they don't have many trees in OZ.
John Byrns
nos...@nospam.com (Don Pearce) wrote:
> On Thu, 25 Oct 2007 13:43:56 GMT, John Byrns <byr...@sbcglobal.net>
> wrote:
>
> >In article <47256a39....@news.plus.net>,
> > nos...@nospam.com (Don Pearce) wrote:
> >
> >> Can you overdrive a class A amp to cutoff?
> >
> >Yes, it is painfully easy.
> >
> >> In my experience what
> >> happens when you overdrive a class A amp is that one device saturates,
> >> and the other sticks with its normal bias condition.
> >
> >No, the coupling capacitor charges up as a result of grid current
> >shifting the bias point so that cutoff becomes even easier.
> >
> >> There is no
> >> circumstance in which I have ever managed to put a class A amplifier
> >> output device into cutoff.
> >
> >You haven't tried very hard then.
> >
>
> The designs I have used must have been better matched in drive level
> between the driver and output stages. They tended to limit almost
> simultaneously so that the drive level to the output stage did not go
> on rising as the input signal increased, just squared off. As I say, I
> never saw an output valve go into cutoff.
That sounds like a dangerous way to go, I would think that running the
drivers that close to "limiting" would create a lot of distortion in the
driver stage before the output stage starts clipping. I think Patrick
just posted, expressing his dislike for this sort of wimpy driver.
Andre Jute
wrote:
> John Byrns wrote:
Holy shit! Did I say yet that Poopie is ignorant and incompetent?
Nah, nobody can be that stupid and uninformed about tube basics.
Poopie must be cracking a joke. For the first time in his life.
Good on yer, cobber! If you can't be smart and informed, at least you
can try to be a clown, give people a giggle.
Andre Jute
Entertainer
Andre Jute
the calculations if I ever sink so low as to build a Class AB amp...
Andre Jute
Class A1 rules the waves!
John Byrns
Andre Jute <fiu...@yahoo.com> wrote:
There are a lot of "stupid and uninformed" people around, there are at
least three people involved in this discussion that have expressed this
same belief as Eeyore, they are Multi-grid, Patrick Turner, and Eeyore.
Andre Jute
> "Don Pearce" <nos...@nospam.com> wrote in message
> >>> Now this poor dumb slow learner Poopie Stevenson, an embarrassment to
> >>> everyone who comes into contact with him, claims to know more than the
> >>> RDH4! Yo, Poopie, in the RDH4 (Newnes 1997) on p 545 we find this
> >>> nugget of authoritative information by F. Langford-Smith B.Sc. B.E.
> >>> himself:
> >>> "Class AB operation indicates overbiased conditions, and is used only
> >>> in push-pull to balance out the even harmonics."
>
> No such thing in the RDH4 at hand.
Do you just lie from habit, Krueger, or are you incapable of using the
contents list or the index of a reference book?
The reference is from RDH4, Chapter 13, Section 1 (ii) Classes of
Operation.
Unsigned out of contempt
Arny Krueger
"John Byrns" <byr...@sbcglobal.net> wrote in message
news:byrnsj-AEE59D....@newsclstr03.news.prodigy.net...
> In article <vpSdnYDnwb8QW73a...@comcast.com>,
> "Arny Krueger" <ar...@hotpop.com> wrote:
>> Actually, there is cancellation regardless of whether one side has ceased
>> conducting or not, because the cancellation comes from the fact that the
>> transfer functions of the two sides are identical but opposite.
>> During the portion of the wave where both sides conduct, there may be
>> cancellation of odd order distortion.
> Are you sure about this? yes.
This looks about right:
http://dave.uta.edu/dillon/ee5301/lecture11.htm
>> In school I was taught the law of half-wave symmetry. Any wave, no matter
>> how distorted, that has matching halves has no even-order distortion.
> Aren't there two symmetry laws, I can never remember the second one, or
> is it the first?
Thanks for the memory jog. Please see the reference. There are lots of
symmertry laws!
>> A wave that is composed of one half of any kind and the other half is
>> zero,
>> has only even-order distortion.
> Could you say that again please?
A wave that is composed of one non-zero half wave of any kind, and the other
half is nothing (zero),
has only even-order distortion.
Andre Jute
wrote:
> Andre Jute wrote:
> > Eeyore <rabbitsfriendsandrelati...@hotmail.com> wrote:
>
> > > Andre Jute wrote:
>
> > > > All of
> > > > that follows logically from Poopie's absurd redefinition of Class A as
> > > > a Class in which "the output device(s)never cease conducting *under
> > > > any signal condition*," (emphasis added). It's ludicrous.
>
> > > It's actually the only accurate definition.
>
> > I've already demonstrated several times that your words "under
> > any signal condition" make your definition grossly inaccurate.
>
> But you're an ignorant cunt and what you say is a load of bollocks.
Even when I'm right? Tsch, tsch, Poopie. That's not even an original
thought. Ron Bales had it first.
> "In a Class A circuit, the amplifying element is biased so the device is always
> conducting to some extent"http://en.wikipedia.org/wiki/Electronic_amplifier#Class_A
You're blowing smoke through your fat arse, Poopie. That reference
doesn't say anything about "under any signal condition." Even
Wikipedia isn't as misinformed as you are. That must be a new record
for you.
> You're confusing cause and effect but your brain is too addled to understand the
> difference.
It still wasn't me who said "under any signal condition". It is still
you who sstupidly said "under any signal condition", thereby voiding
the rest of the definition of Class A operation.
>
> Graham
You're a clown, Poopie. Wiki in, Poopie out. Same as GIGO.
Unsigned out of contempt