PL509??? EL519?? EL509??
Tube747
What are the difference between PL509, EL509 and EL519? If an amplifier using
PL509 as the output tube, which one is the direct substitute to improve the
performance? EL509 or EL519? Any modification require with those tubes it
replacing the PL509?
Thanks!
Chris Morriss
<tub...@aol.com> writes
PL519 is an updated version of the PL509. The EL519 is the same part
but with a conventional 6.3v heater.
European designations are E for 6.3v heater, P for 0.3A heater, and U
for 0.1A heater. (P and U parts were originally intended for series
heater chains).
Chris Morriss
Also at chris....@lakecommunications.com
Mikkel C. Simonsen
>
> Hello RATs!
> What are the difference between PL509, EL509 and EL519?
Heaters. EL types use 6.3V heaters and the PL5x9 types use 40V heaters.
> If an amplifier using PL509 as the output tube, which one is
> the direct substitute to improve the performance? EL509 or
> EL519?
PL519 would be a direct substitute. The PL519 is probably better than
the PL509 in a TV - it may not be better at all when used in an amp.
Substituting an EL5x9 would/could require a major re-design of the
powersupply - but why? The EL tubes are no better or worse than the PL
tubes as they are identical - except for the heater, which doesn't
influence the performance of the tube.
> Any modification require with those tubes it replacing the PL509?
If you want to use EL5x9 tubes you would have to check how the heater
supply in the amp works, to make sure the powersupply would work without
the PL5x9 heaters connected. You would also have to install a new
transformer to supply the EL5x9 heaters.
Best regards,
Mikkel C. Simonsen
> Thanks!
Patrick Turner
"Mikkel C. Simonsen" wrote:
Perhaps what Denis might say about the PL509, or EL509
might change the ideas people have about this tube as being a bit non
linear,
and better off in a TV.
I haven't used them but I have serviced an EAR509 mono amp
which manages 100 watts at 0.2% thd from two tubes, AB1,
but it does have a total of 44 dB od NFB to achieve the outcome.
Lord knows what the 509 does when "normally" plate loaded and with no NFB,
methinks they would be no more linear than any other tetrode.
Bear in mind that 2 x 6550 in tetrode are supposed to have 0.6% thd
when Ea = 440v, Eg2 = 300v, and about 4.4 k RL, and I guess a fair amount of
class A.
In the EAR 509, there is no possibility of using alternative tubes, such as
6550,
since the heaters are 40 volts, and also because the anode loads are too low
for 6550. The 509 does have an enormous peak current ability,
which is why Tim DeParavicini was inclined to use them.
The 509 has those horrible sockets with 9 pins.
PL509 has 40 v heaters.
Don't ask me why they would use an oddball socket,
instead of an octal, but all that was driven by accountants
telling makers that the 9 pin arrangement was cheaper, like a giant EF86,
and the series heater strings meant the 6.3 volt heater winding wasn't
required.
The 509 series tubes now made should all have octal pinouts, and 6.3v
heaters,
and no anode top cap, with the arrangement of pins like the 6FW5.
While they are at it, the makers should increase the Pd rating to 55 watts.
Patrick Turner.
Pär
> 6550,
> since the heaters are 40 volts, and also because the anode loads are too low
>
> for 6550. The 509 does have an enormous peak current ability,
> which is why Tim DeParavicini was inclined to use them.
> The 509 has those horrible sockets with 9 pins.
> PL509 has 40 v heaters.
> Don't ask me why they would use an oddball socket,
> instead of an octal, but all that was driven by accountants
> telling makers that the 9 pin arrangement was cheaper, like a giant EF86,
> and the series heater strings meant the 6.3 volt heater winding wasn't
> required.
>
> The 509 series tubes now made should all have octal pinouts, and 6.3v
> heaters,
> and no anode top cap, with the arrangement of pins like the 6FW5.
> While they are at it, the makers should increase the Pd rating to 55 watts.
>
> Patrick Turner.
Aren't KT90 (type "something") based upon EL509/519?
And KT90 are supposed to be exchangable with KT88/6550 (with some bias
adjustment)?
Well... I would have guessed PL519 would sub for 6550 (except for
heater voltage, and socken, and anode cap, and size, and...), but that
kind of logic obviously didn't hold :-)
If it would hold it would mean the famous and higly regarded highend
6PRAT1 would have been based upon a lousy PL509 sweep tube which is
good for nothing (no, I didn't say that)...
mvh /Pär
p.s
Tele lists EL500 (EL/PL-500/504 is a smaller forerunner of
EL/PL-509/519) as 30W/5% "klirr" at 300V (A/g2) pentode -55V class B
output with Raa 3.5k.
Not bad for a lousy PL504 defection tube...
p.p.s.
There is a PL505 as well which is a weaker (Pa) PL509/519
d.s.
Patrick Turner
Pär wrote:
> --- snippetysnipp ---
> > In the EAR 509, there is no possibility of using alternative tubes, such as
> > 6550,
> > since the heaters are 40 volts, and also because the anode loads are too low
> >
> > for 6550. The 509 does have an enormous peak current ability,
> > which is why Tim DeParavicini was inclined to use them.
> > The 509 has those horrible sockets with 9 pins.
> > PL509 has 40 v heaters.
> > Don't ask me why they would use an oddball socket,
> > instead of an octal, but all that was driven by accountants
> > telling makers that the 9 pin arrangement was cheaper, like a giant EF86,
> > and the series heater strings meant the 6.3 volt heater winding wasn't
> > required.
> >
> > The 509 series tubes now made should all have octal pinouts, and 6.3v
> > heaters,
> > and no anode top cap, with the arrangement of pins like the 6FW5.
> > While they are at it, the makers should increase the Pd rating to 55 watts.
> >
> > Patrick Turner.
> Hi,
>
> Aren't KT90 (type "something") based upon EL509/519?
Gee the guts of the KT90 look very different.
>
> And KT90 are supposed to be exchangable with KT88/6550 (with some bias
> adjustment)?
Yes, and KT90 can produce a lot more power into lower loads,
since their current ability is higher.
>
> Well... I would have guessed PL519 would sub for 6550 (except for
> heater voltage, and socken, and anode cap, and size, and...), but that
> kind of logic obviously didn't hold :-)
Sure, maybe the 509 could be cajoled into working with 6550 type
load values, but not the other way around if the load values are a lot lower.
The 509 has good current ability, splendid current ability, in fact,
so lower load values are tolerated.
> If it would hold it would mean the famous and higly regarded highend
> 6PRAT1 would have been based upon a lousy PL509 sweep tube which is
> good for nothing (no, I didn't say that)...
6RAT1, not 6PRAT, please, a "prat" in the UK, or Oz is about equal to
a Richard Cranium, or a Jerk.
Patrick Turner.
Simon van de Laak
http://www.builditmall.com/tubebuilder/cgi-bin/shopclerk.exe?Page=scstore/de
tail&ID=EL509MK2-RU&Session=02452603012216
Regards,
Simon
"Patrick Turner" <in...@turneraudio.com.au> schreef in bericht
news:3DE02AF4...@turneraudio.com.au...
Simon van de Laak
http://www.builditmall.com/tubebuilder/cgi-bin/shopclerk.exe?Page=scstore/de
tail&ID=EL509MK2-RU&Session=02452603012216
Regards,
Simon
"Simon van de Laak" <van.d...@hccnet.nl> schreef in bericht
news:arrc7s$3ro$1...@news.hccnet.nl...
Pär
> > > Patrick Turner.
> > Hi,
Hi,
> >
> > Aren't KT90 (type "something") based upon EL509/519?
>
> Gee the guts of the KT90 look very different.
Just what I've heard. But aren't Type 1, 2 and 3 kind of different?
Another hearsay though. Have no KT90 of any version around here, but
loads of those PL.
>
> >
> > And KT90 are supposed to be exchangable with KT88/6550 (with some bias
> > adjustment)?
>
> Yes, and KT90 can produce a lot more power into lower loads,
> since their current ability is higher.
>
> >
> > Well... I would have guessed PL519 would sub for 6550 (except for
> > heater voltage, and socken, and anode cap, and size, and...), but that
> > kind of logic obviously didn't hold :-)
>
> Sure, maybe the 509 could be cajoled into working with 6550 type
> load values, but not the other way around if the load values are a lot lower.
> The 509 has good current ability, splendid current ability, in fact,
> so lower load values are tolerated.
Yepp, 200-250mA is a lot lesser than 0,5A (same for PL505 btw. but
that one is rare).
>
> > If it would hold it would mean the famous and higly regarded highend
> > 6PRAT1 would have been based upon a lousy PL509 sweep tube which is
> > good for nothing (no, I didn't say that)...
>
> 6RAT1, not 6PRAT, please, a "prat" in the UK, or Oz is about equal to
> a Richard Cranium, or a Jerk.
I'm sorry about that. Meant it in the PRaT:ty way which have another
Naim than Richard C.
>
> Patrick Turner.
mvh /Pär
Mikkel C. Simonsen
>
> 6RAT1, not 6PRAT, please, a "prat" in the UK, or Oz is about equal to
> a Richard Cranium, or a Jerk.
So you think "rat" has a more positive sound than "prat"?
I think most people prefer prats to rats - at least if the rats are
genuine rodents... ;-)
Pär
Don't say so, I used to have rats as pets. Besides: They have good
taste in tubes as well. They seems to prefere to put their teeths into
an old Telefunken box with the plastic wrapping before any old
miniwatt/siemens box...
mvh /Pär
Patrick Turner
"Mikkel C. Simonsen" wrote:
> Patrick Turner wrote:
> >
> > 6RAT1, not 6PRAT, please, a "prat" in the UK, or Oz is about equal to
> > a Richard Cranium, or a Jerk.
>
> So you think "rat" has a more positive sound than "prat"?
Most prats in the world don't survive real well,
being awkward, and have trouble finding a wife.
But the average rat has now co-existed with humanity, and huwomanity,
since we started living in caves where they already were living.
The rat is a bright creature. When we started building framed houses
by the dozen, the rat followed us out of the cave, and into the ideal
heated home environment just the other side of the sheetrock
in the walls and ceiling. They get fat on our garbage.
OK, it plagued us, and it robs 10% of the third
world's food, and it is a damnable pest, but it is a great survivor.
>
> I think most people prefer prats to rats - at least if the rats are
> genuine rodents... ;-)
Dozen madder much, does it?
I think the 6RAT is a long way off.
Patrick Turner.
Tube747
Tube747
>supply in the amp works, to make sure the powersupply would work without
>the PL5x9 heaters connected. You would also have to install a new
>transformer to supply the EL5x9 heaters.
Can I use a low voltage regulator to drop the voltage from 40V to 6.3V from the
filament windings of power transformer secondary?
Tube747
>I haven't used them but I have serviced an EAR509 mono amp
>which manages 100 watts at 0.2% thd from two tubes, AB1,
>but it does have a total of 44 dB od NFB to achieve the outcome.
I heard that Tim De Paravicin latest amplifier using a new method called
"Enhanced Triode" for the output tubes on his new amplifier which also use the
sweep tubes (such as EL519 or EL509) . Can the EAR 509 also wire in "Enhanced
Triode mode"?
>In the EAR 509, there is no possibility of using alternative tubes, such as
>6550,
>since the heaters are 40 volts, and also because the anode loads are too low
Again, is this possible to use a low voltage regulator to drop the voltage to
6.3V
A funny question I would like to ask you. Do you think an EAR 509 better off
using a different power transformer (higher current for class A and proper
lower voltage secondary filament winding for EL5x9 type tube) to run the
amplifier in pure class A, also wire in enhanced triode mode as Paravicini does
to his latest design.
What will going to be happen?
Thank you!
Fred Nachbaur
You can, but it would be horribly inefficient. Let's say you want to use
an EL509, it has a filament current of 2.0 amperes. You have to drop
40-6.3 = 33.7 volts. Multiply by current (2.0) and you have 67.4 watts
that you have to burn off with the regulator. In other words, you have
to burn up 5.4 times as much power in the regulator as is used by the
valve's filament!
What's more, there's no way that a 40 volt transformer designed to run a
PL509 (0.3 amperes) will be capable of delivering six times as much
current. You'll end up with a very hot regulator and a very hot
transformer. But only for a short while.
Cheers,
Fred
--
+--------------------------------------------+
| Music: http://www3.telus.net/dogstarmusic/ |
| Projects, Vacuum Tubes & other stuff: |
| http://www.dogstar.dantimax.dk |
+--------------------------------------------+
Patrick Turner
Tube747 wrote:
Probably no, because the 40v heater winding for a pair of 509
will have a 0.6 amp rating, but the 6.3 volts for two x KT88/6550
will need 3.6 amps.
Even if the '88 heaters are seriesed, you need 1.8 amps.
To use '88, a 40v to 12.6v / 6.3v could be used, or a mains to
6.3v.
Patrick Turner.
Patrick Turner
Tube747 wrote:
> Hi Patrick Turner!
> >I haven't used them but I have serviced an EAR509 mono amp
> >which manages 100 watts at 0.2% thd from two tubes, AB1,
> >but it does have a total of 44 dB od NFB to achieve the outcome.
>
> I heard that Tim De Paravicin latest amplifier using a new method called
> "Enhanced Triode" for the output tubes on his new amplifier which also use the
> sweep tubes (such as EL519 or EL509) . Can the EAR 509 also wire in "Enhanced
> Triode mode"?
His idea of "Enhanced Triodes" is a way of driving tubes outa their cotton
pickin minds, ie, well into class AB2, with little class A% in the total power
output.
He done this with one design using 20 x 12AX7 per channel.
There would be nothing to gain by re-jigging the EAR509 as a triode amp,
except a loss in power of 50% in class A1, and some loss if driven into class
AB2, and I doubt the plate loaded 6AQ8 LTP bootstrapped driver would cope
with the grid current of the output stage, certainly not as well as a McIntosh.,
which uses a topology very similar to the EAR509.
>
> >In the EAR 509, there is no possibility of using alternative tubes, such as
> >6550,
> >since the heaters are 40 volts, and also because the anode loads are too low
>
> Again, is this possible to use a low voltage regulator to drop the voltage to
> 6.3V
Nope, see my other post.
>
>
> A funny question I would like to ask you. Do you think an EAR 509 better off
> using a different power transformer (higher current for class A and proper
> lower voltage secondary filament winding for EL5x9 type tube) to run the
> amplifier in pure class A, also wire in enhanced triode mode as Paravicini does
> to his latest design.
The EAR509 has a very well sized power tranny, and is quite adequate
for class AB pentode operation, giving enough class A
power for most listeners. The vast amount of NFB cleans up whatever
open loop thd.
>
>
> What will going to be happen?
I have not seen any schematic for the "enhanced triode operation"
of EL509, but I assume the "enhanced" part comes from combining
AB2 operation with a "unity coupled" output stage, like a McIntosh,
where the anode and cathode windings have equal turns.
The unity coupling does at least two things, first to provide heaps
of local series voltage feedback in the output stage, and second to raise
the input impedance, even with gridcurrent being drawn.
The driver tubes then don't experience the low impedance that
high amounts of gridcurrent normally cause, so their voltage swing ability is not
impaired
by the low load of the output stage.
McIntosh use a 1/2 12AX7 CF to drive the output tubes.
In fact, McIntosh were doing what TDeP does 25 years before the 1970s
EAR509 came out.
This AB2 mode can be done by any DIY person with 6L6 in triode,
with a CF driver stage added to an existing amp.
Thus it is possible to get 30 watts AB2 from 2 x 6L6 in triode, not just the lousy
16 watts AB1.
A pair of 807 can give 80 watts in AB2 pentode.
thd is up around 14%, but NFB can straighten it all out to make it measure pretty.
Not really my scene all this, I prefer to have a mild amount of
CFB in an output stage, and then also have global NFB,
and to equal the measurements of Tde P I need only 20 dB of total NFB,
instead of 44 dB.
And one stage less in the tube line up
Patrick Turner.
>
>
> Thank you!
Tim Williams
news:3DE3722D...@turneraudio.com.au...
> His idea of "Enhanced Triodes" is a way of driving tubes outa their cotton
> pickin minds, ie, well into class AB2, with little class A% in the total
power
> output.
Ohh Pat, how easily you forget!
Isn't Enhanced Triode mode driving a pentode via screen?
A small cathode follower, perhaps 12AU7 or 5687 would work just fine
for CF-driving most sweeps, however the signal source has to be large
due to the low g2-p Gm. Perhaps a 500V supply for all; this would
allow high power output and large linearity in the driver stages.
Tim
--
"Hey, back in high school I was voted most likely to be a Hillbilly,
mental patient or Chimpanzee!"
- Homer Simpson
Patrick Turner
Tim Williams wrote:
> "Patrick Turner" <in...@turneraudio.com.au> wrote in message
> news:3DE3722D...@turneraudio.com.au...
> > His idea of "Enhanced Triodes" is a way of driving tubes outa their cotton
> > pickin minds, ie, well into class AB2, with little class A% in the total
> power
> > output.
>
> Ohh Pat, how easily you forget!
> Isn't Enhanced Triode mode driving a pentode via screen?
Oh, you mean screen driven triodes, why, that's been done for years.....
RF amps used this idea.....
But I thought TdeP had "Enhanced triodes" in his 12AX7 based amps.
There is no screen in a 12AX7.
I could be wrong.
Now I know what happened, it was the truly horrible toothache
I had yesterday.
(The new dentist I went to had to redo the
previous dentist's work, and even more agony prevailed last night.
Things are a lot better today.
And dentist No2 is an old fart who knows more, has had more experience,
and who has tried to save the tooth rather than extract.
No1 dentist wanted to extract it because I wouldn't
agree to $3,200 crown installation. He is keen on extracting money from the
pocket.
But his attempt at filling had left me in pain for months.
The new dentist is a lot cheaper,
and regards extractions as a last resort, and
offered me options which would keep the tooth, me, and him, reasonably happy.)
>
>
> A small cathode follower, perhaps 12AU7 or 5687 would work just fine
> for CF-driving most sweeps, however the signal source has to be large
> due to the low g2-p Gm. Perhaps a 500V supply for all; this would
> allow high power output and large linearity in the driver stages.
Probably the 509 will work very nicely with G2 as the control grid,
and yes, the voltage drive is as high as it is in the EAR509,
which is a McIntosh style of circuit.
So like the EAR509, which has three cascaded LTPs, with the last of them
bootstrapped
off the OPT to get the high drive voltage, a similar thing could be done
with the G2 drive, except that a CF has to be added to cope
with the screen current.
T de P makes weird and wacky designs and he has been the darling of the
hi-fi press for years and gets away with it, but I maintain that any dedicated
DIY
person can do just as well for sound quality without addopting the queer
circuits he uses.
Enhanced Triode, if it means screen drive, is used in every UL amp to apply
NFB from the anode back to the screens.
Just like Ultralinear isn't exactly completely ultra anything,
I am not so sure Enhanced triode means the triode is in any way
enhanced. Its just a catchy market ploy, but a name has to be given....
Audiophiles are more likely to be impressed by "enhanced triode"
than say "paravicini concoction"
Anyway, one does need a fair old screen signal, maybe a gain of 2 or 3 is
possible from
most power tetrodes using ET topology.
To get that high drive signal means the THD will be high in the drive stage
like it is in a McIntosh, or EAR509.
Thus lots more NFB is needed to reduce it to the low levels in amps
which are simpler.
I have one amp where the driver stage voltage supply is 600v,
so that high value R loads feed the DC to the 6CG7 LTP.
thd is very minimal at 50 vrms form each anode.
Thus the contribution to overall thd by the drive amp is minimal.
About 150 vrms is available, and thd is still only 1% or 2 %,
and it could be used in an ET circuit, or in a McI circuit,
but if the output stage also makes 1%, then its easy to have 3%
and 20 dB is needed to reduce it all down to 0.3%.
But a well made Williamson has 0.1%, and its because the
amp with no global FB makes 1%, and the same 20 dB of
NFB reduces it to 0.1%.
I feel its better to allow the drive voltage to
higher than usual but only if the linearity of the driver signal can be
maintained.
A 300B amp needs every bit of driver linearity it can get.
and so do amps using CFB on the OPT, or unity coupling.
Bootstrapping from the OPT does allow a high drive voltage,
but the thd is still going to creep up from
0.1% at 20 vrms drive voltage to 1% to 3% at 120 vrms.
Patrick Turner.
Tim Williams
> But I thought TdeP had "Enhanced triodes" in his 12AX7 based amps.
> There is no screen in a 12AX7.
Hmmm...
> I could be wrong.
Well it can't be too weird. Oddest I can think of is something
Steve Bench would come up with. ;-) And even then, that works
best for low-mu tubes.
Worst might be class A(B)2, but that's not unusual at all.
It's just that 12AX7 isn't made for that.
<Snip dental ouchage>
> T de P makes weird and wacky designs and he has been the darling of the
> hi-fi press for years and gets away with it..
Yep, that's the impression I get.
I like that theory. Exloration = fun, right?
But alas, tried and true wins out in any case. Sigh.
> Enhanced Triode, if it means screen drive, is used in every UL amp to
apply
> NFB from the anode back to the screens.
Yep, in a way. But it's not triode, it's a pentode with feedback.
ET is completely different dare I say; you can draw a load line on
the G1=0V graph instead of the G2=+250V (or whatever it may be) graph.
I think it makes sense to call it enhanced - the 'zero-bias' point
occurs at a knee, and thus a very low voltage, allowing very much
higher power outputs than a triode-wired pentode.
If you only need 200V of screen drive, that's not too bad. But
4 or 500V would be sadistic (though still attainable).
One interesting tidbit is, you could design a class AB amp, going
right up to the edge of plate dissipation at full power, just by
limiting the screen voltage used. Plate current can always go
higher with a higher screen voltage.
A tube rated for high voltage, strung between +500 and -500V (using
a FWB rectifier, which could still use a tube rectifier for the\
positive supply if you must) ought to provide some linearity.
Alternately, you could wind a Big Honking choke, and run it from
a bit less voltage, and get better linearity too. Unfortunately,
the high voltage means high fields, making for a hard part to build.
Patrick Turner
Tim Williams wrote:
> "Patrick Turner" <in...@turneraudio.com.au> wrote in message
> news:3DE4363E...@turneraudio.com.au...
> > But I thought TdeP had "Enhanced triodes" in his 12AX7 based amps.
> > There is no screen in a 12AX7.
>
> Hmmm...
>
> > I could be wrong.
>
> Well it can't be too weird. Oddest I can think of is something
> Steve Bench would come up with. ;-) And even then, that works
> best for low-mu tubes.
> Worst might be class A(B)2, but that's not unusual at all.
> It's just that 12AX7 isn't made for that.
I don't mind folks using tubes in ways they were not "meant for"
I see no problem with "technical license" just like I might use poetic
license
to describe the "bullshitesque ramblimations of bastarditious entities"
now going on between old adversaries elsewhere in this group.
>
>
> <Snip dental ouchage>
Less ouchage today, no need to attack myself in desperation with a cold
chisel,
hammer, and longnose pliers.
>
>
> > T de P makes weird and wacky designs and he has been the darling of the
> > hi-fi press for years and gets away with it..
>
> Yep, that's the impression I get.
> I like that theory. Exloration = fun, right?
Precisely, exploration could be fun.
But much exploring is just another race.
Straight up one side of the mountain, and ass over head down the other
side, taking the skin off the shins.
It is better to ascend the moutain gracefully, taking in the vistas of
wonder,
using a route which takes us around the mountain, to be able to experience
the
mountain to the fullest, since we a foolish to conquer it.
>
> But alas, tried and true wins out in any case. Sigh.
There are always designs for the easily bored.
>
>
> > Enhanced Triode, if it means screen drive, is used in every UL amp to
> apply
> > NFB from the anode back to the screens.
>
> Yep, in a way. But it's not triode, it's a pentode with feedback.
But if there was no forward signal in the amp, from the input to output,
and we apply a signal to the output, the signal is reflected to the output
tubes
via the transformer, and signal also applied to the screens, which tend to
oppose the signal we apply to the output.
If there was no global NFB, indeed the UL screen FB is a case of enhanced
triode operation.
All harmonic distortion voltages apply themselves backwards into
the amp, where they get amplified in reverse, so they get repressed.
>
> ET is completely different dare I say; you can draw a load line on
> the G1=0V graph instead of the G2=+250V (or whatever it may be) graph.
> I think it makes sense to call it enhanced - the 'zero-bias' point
> occurs at a knee, and thus a very low voltage, allowing very much
> higher power outputs than a triode-wired pentode.
I have seen a few ET curves for pentode/tetrode tubes,
I guess a wider V swing is possible.
But with 6L6/807 in normal class AB2, you can attain a similar much
wider load swing if you make the drive amp capable of powering into the
grid current of the output tubes.
>
> If you only need 200V of screen drive, that's not too bad. But
> 4 or 500V would be sadistic (though still attainable).
Well, its possible to get a swing of 2 x 100 vrms easily by using
a couple of 6V6/EL84 or 6SN7 in triode, followed by a CF to
power a screen grid, or G1 in AB2, all without bootstrapping from the output
stage.
>
> One interesting tidbit is, you could design a class AB amp, going
> right up to the edge of plate dissipation at full power, just by
> limiting the screen voltage used. Plate current can always go
> higher with a higher screen voltage.
> A tube rated for high voltage, strung between +500 and -500V (using
> a FWB rectifier, which could still use a tube rectifier for the\
> positive supply if you must) ought to provide some linearity.
> Alternately, you could wind a Big Honking choke, and run it from
> a bit less voltage, and get better linearity too. Unfortunately,
> the high voltage means high fields, making for a hard part to build.
Keep on thinking........
The entrancing thing about tubes is the many ways they can be hooked up.
Patrick Turner.