Krell downgrade
dco...@my-deja.com
of a sceptic that one can hear differences between amplifiers, but I
reckoned that the chance to get the newer model second-hand doesn't
come up very often, at least not of this brand in the UK, and no doubt
it would be even better than its predecessor, as well as more reliable
and less heat dissipating.
I can hear the difference. It's very marked, to a degree that
surprises me with broadly comparable models of the same manufacturer.
But I don't like it. The bass is much firmer, definitely more
realistic; but all that serves is to annoy the neighbours. Meantime,
the mid and high end are grey and thin and lifeless compared with what
I've come to like.
I know that one gets used to a particular sound, and I should allow
time for re-habituation. But I must say I'm dismayed to have torn the
heart out of a much-loved system and am keen to find another KSA
quickly.
This is so out of line with reviews and general consensus. Is it me
that is wrong, or the rest of the world? Other equipment used is
Wilson System 5, and Meridian 502 and 508 preamp and CD player.
Sent via Deja.com
http://www.deja.com/
Stewart Pinkerton
You might try better speakers. The Wilson V is notorious for hard
sound (although with great dynamics for a small speaker), maybe you
are just now hearing them at full power? OTOH, I am *very* surprised
that you are hearing any *real* difference between the KAV250a and the
FPB250.
--
Stewart Pinkerton | Music is art, audio is engineering
CCSman
>that you are hearing any *real* difference between the KAV250a and the
>FPB250.
It's the KSA 250 that the original poster referred to, not a KAV 250a
Rick Stadelmaier
said some have been a backwards step.
I'm not sure of which models they were.
I have found them to be a little inconsistent, some have sounded
ordinary.
Others have sounded excellent.
Rick.
--
Rick Stadelmaier
Equinox Audio
http://www.equinoxaudio.com.au
equ...@pip.com.au
Sydney, Australia
gy
news:918qus$8l1$1...@bourbaki.localdomain...
It's all about the system -- an amp by itself just sits there and
doesn't make any sound at all (I hope).
Sounds like you formerly had a wonderfully matched system, yet now,
you've still got all excellent gear, but, the "system" is no longer
"matched" to present the harmonic, musical experience you once
enjoyed -- damn, I feel for you - that's happened to me. Here's what
I'd do -- contact your speaker manufacturer - Hopefully, Wilson's
people will not be too political and they'll ask you intelligent
questions about what you enjoyed most from your former system. If
they've done their homework, they'll likely have a list of great amps
(in different price ranges from different manufacturers with
different models numbers) that the can consult with you to recommend
for your particular needs.
Get this friend, many people deep in the audio business don't like to
admit it publicly, because it depletes sales in the big heavy duty
gear, yet often the "baby" amps are the most fun to listen to and
exhibit the most musical reproductions off the recordings -- I have a
dozen theories why, yet I'm not an amp designer, so I can really say
why. When you've got to use the big power guns to drive a very
difficult speaker load, then you've got to do that. However, when you
don't, put a gun to an experienced Levinson dealer, he'll admit the
"60 to 100 watt Baby" is the one they hook up for after hour parties.
An experienced Krell dealer will likely recommend the little stereo
charmer and -- should it properly handle the speaker load. I myself
regret saying goodbye to both a ancient 50 Stax amp (at the time it
simply didn't have enough power to drive what I needed) and I also
miss a Jeff Rowland Design Group Model 1 rated at 60 watts stereo --
not powerful amps, yet the most fun listening hi-fi amps I've yet to
hear. I realize your new system might be a heart breaker, yet don't
fret, it's possible that someone out there who wants Krell and
actually needs the power you have will trade you back.
If a system doesn't match, it doesn't matter what it's made of.
Good luck.
gy
Anton Meyer
dco...@my-deja.com wrote:
<snip>
> Meantime, the mid and high end are grey and thin and lifeless
> compared with what I've come to like.
<snip>
I auditioned these monoblocks a while back, albeit not with the
Watt/Puppy. The adjectives you use here are very similar to my own
thoughts at the time. I can't comment usefully on the KSA-250 as I
heard one in a different system and room many months previously, but
I can say I enjoyed listening to it. My observation is that many
believe the FPB series to be inferior to some of the older models.
Of course your mileage may vary, but as you are UK based I would
strongly suggest you take a look at Chord.
Anton Meyer
Stewart Pinkerton
In that case, I'm even more surprised. IMNVHO, the KSA 250 is one of
the best amps ever made, by anyone.
CCSman
>
>In that case, I'm even more surprised. IMNVHO, the KSA 250 is one of
>the best amps ever made, by anyone.
>
Agreed- the KSA250 is beyond reproach sonically; but it is hard to
live with in terms of size and heat. Krell, as much as any
manufacturer, has evolved in its sound, and I suspect that the
original poster prefered the roundeer sound that the KSA250 made-
Many say that when the 'S' series came out, Krell sound took a turn
for the worse. I'm note so sure it's the sustained bias plateau
operation, as if you look at idle current of, say a KSA 250, it's
clear that not withstanding the fact that Krell claims it's a pure
class A amp, it can not be, but rather is an A/B amp that is
unusually high biased into class A.
Didn't Einstein say make everything as simple as possible, but not
any simpler?
Jim Susky
(snip)
>Get this friend, many people deep in the audio business don't like to
>admit it publicly, because it depletes sales in the big heavy duty
>gear, yet often the "baby" amps are the most fun to listen to and
>exhibit the most musical reproductions off the recordings -- I have a
>dozen theories why, yet I'm not an amp designer, so I can really say
>why. When you've got to use the big power guns to drive a very
>difficult speaker load, then you've got to do that. However, when you
>don't, put a gun to an experienced Levinson dealer, he'll admit the
>"60 to 100 watt Baby" is the one they hook up for after hour parties.
>An experienced Krell dealer will likely recommend the little stereo
>charmer and -- should it properly handle the speaker load.
Pearson, in TAS used to ruminate about this. The small amps seemed to have
an "agility", a rightness, lacking in the bigger stuff (paraphrasing here
obviously, and too lazy to unpack the back issues).
Still the message was clear - bigger is not necessarily better.
And check out the high-sensitivity speaker/flea power SET crowd. Those guys
are groovin' on 3 watts per side.
I have a friend who has triamped horn system using push-pull quicksilvers,
pro audio drivers (and the horns from his dismembered Klipschhorn. TD 2001
tweet, Community model 40 (400?) mid, JBL woof. This is not flea power, but
it is high sensitivity, and it has exceptional clarity, dynamics, and ease.
This load is not at all difficult, and the amps are not costly by specialty
audio standards, and it works big time.
Stewart Pinkerton
>>>It's the KSA 250 that the original poster referred to, not a KAV 250a
>>
>>In that case, I'm even more surprised. IMNVHO, the KSA 250 is one of
>>the best amps ever made, by anyone.
>>
>Agreed- the KSA250 is beyond reproach sonically; but it is hard to
>live with in terms of size and heat. Krell, as much as any
>manufacturer, has evolved in its sound, and I suspect that the
>original poster prefered the roundeer sound that the KSA250 made-
>
>Many say that when the 'S' series came out, Krell sound took a turn
>for the worse.
Yup, the S series was not their finest hour.........
> I'm note so sure it's the sustained bias plateau
>operation, as if you look at idle current of, say a KSA 250, it's
>clear that not withstanding the fact that Krell claims it's a pure
>class A amp, it can not be, but rather is an A/B amp that is
>unusually high biased into class A.
It *is* a class A amp up to 250 watts into 8 ohms, which is its rated
output. At lower impedances, it is of course class AB, as is true for
any other class A power amp.
>Didn't Einstein say make everything as simple as possible, but not
>any simpler?
Indeed so, and a class A amp is conceptually as simple as it gets. The
implementation may be a bit trickier.............
BEARlabs
these two amps might as well be from different manufacturers, since
they were engineered by different people at different times. They use
somewhat different topologies, and operate differently.
I rather think that the KSA series was rather etched and "screechy"
on the top end, and had an odd effect in the bass - one that reacted
well with some speakers and horribly with others... (which is why
many folks opted for the very inductive SYMO/Krell speaker cables
with that series of amps)
The newer series seems to be fatter sounding, and warmer, but somehow
a bit subjectively "dead" sounding overall. An improvement IMHO, as I
really never liked the KSA series at all. (But, I wish I had Dan's
sales figures...)
All this notwithstanding the claims that distortion below something
like 0.1% from an amp is inaudible - I have found that it is fairly
easy to predict the subjective sound of an amp merely by looking at
the leading edge of its square wave response on a good scope, and it
works the other way as well.
IMHO, neither is a particularly clean, nor neutral amplifier. Neither
is technically superb, but both will dump huge amounts of voltage and
current into a load.
--
_-_- BEAR Labs
"Custom Handcrafted Audio Components & Cables"
Rick Stadelmaier
> >operation, as if you look at idle current of, say a KSA 250, it's
> >clear that not withstanding the fact that Krell claims it's a pure
> >class A amp, it can not be, but rather is an A/B amp that is
> >unusually high biased into class A.
>
> It *is* a class A amp up to 250 watts into 8 ohms, which is its rated
> output. At lower impedances, it is of course class AB, as is true for
> any other class A power amp.
It is most certainly *not* class A up to 250 watts.
If you do the math, you will find this to be impossible.
Rick
Equinox Audio
http://www.equinoxaudio.com.au
equ...@pip.com.au
Sent via Deja.com
http://www.deja.com/
Francois Yves Le Gal
wrote:
>It is most certainly *not* class A up to 250 watts.
I would concur here. This Krell model looks like a solid class A up
to 60 or 80 W on 8 Ohms, no more.
>If you do the math, you will find this to be impossible.
Well, it's possible, but not with the power supplies, transistors and
heatsinks used. A 250 W pure class A amp would need at least a 1 KW
power supply and yards and yards of heat sinks.
Stewart Pinkerton
>On 19 Dec 2000 22:15:00 GMT, Rick Stadelmaier <rick_e...@my-deja.com>
>wrote:
>
>>It is most certainly *not* class A up to 250 watts.
>
>I would concur here. This Krell model looks like a solid class A up
>to 60 or 80 W on 8 Ohms, no more.
This a totally incorrect statement. The KSA250 *is* pure class A up to
250 watts into 8 ohms, as a simple check on its power consumption at
idle (close to 1.5kW) will show.
>>If you do the math, you will find this to be impossible.
>
>Well, it's possible, but not with the power supplies, transistors and
>heatsinks used. A 250 W pure class A amp would need at least a 1 KW
>power supply and yards and yards of heat sinks.
This is sheer ignorance of the basic technical details of one of the
finest power amplifiers ever made. In point of *fact*, the KSA 250 has
a 5kW power supply (it's rated to output 2kW per channel *continuous*
into 1 ohm), while its huge heatsinks are rather more than a yard long
and very sharp-edged - this is not an amplifier to be handled easily!
It also weighs 65kg.
--
Stewart Pinkerton | Music is art, audio is engineering
-----= Posted via Newsfeeds.Com, Uncensored Usenet News =-----
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Rick Stadelmaier
>
> I would concur here. This Krell model looks like a solid class A up
> to 60 or 80 W on 8 Ohms, no more.
Somewhere around that, yes.
> >If you do the math, you will find this to be impossible.
>
> Well, it's possible, but not with the power supplies, transistors and
> heatsinks used. A 250 W pure class A amp would need at least a 1 KW
> power supply and yards and yards of heat sinks.
Yes, but more to do with standard wall outlets not supplying enough
power.
Rick.
Equinox Audio
http://www.equinoxaudio.com.au
equ...@pip.com.au
Stewart Pinkerton
>> > I'm note so sure it's the sustained bias plateau
>> >operation, as if you look at idle current of, say a KSA 250, it's
>> >clear that not withstanding the fact that Krell claims it's a pure
>> >class A amp, it can not be, but rather is an A/B amp that is
>> >unusually high biased into class A.
>>
>> It *is* a class A amp up to 250 watts into 8 ohms, which is its rated
>> output. At lower impedances, it is of course class AB, as is true for
>> any other class A power amp.
>
>It is most certainly *not* class A up to 250 watts.
>If you do the math, you will find this to be impossible.
Here come da math!
Power consumption of the KSA250 at idle is rated at 120 volts, 12
amps. This is 1,440 watts. A class-A push-pull amplifier has a
theoretical maximum efficiency of 50%, typically more like 35%. Now,
1440 x 0.35 = 504, which just happens to be twice 250 watts for this
stereo amplifier.
Care to explain why this is 'impossible'?
--
Stewart Pinkerton | Music is art, audio is engineering
Stewart Pinkerton
Regarding KSA and FPB series Krell amps:
>IMHO, neither is a particularly clean, nor neutral amplifier. Neither
>is technically superb, but both will dump huge amounts of voltage and
>current into a load.
OTOH Randy, what weight should one give to completely unsubstantiated
opinions from a competitor?
BEARlabs
full schematic of the KSA or Reference series of that era, but it
seems to me that there is a "trick" employed in the bias circuit.
Actually, having never had one *here* on my bench to test, I
can not be sure on that basis either - that would tell me if my
idea is correct or not.
I think this is why the KSA appears to play louder than an amp
of supposedly equal power - at least this has been my experience.
I someone has a full schematic handy we could see for sure.
Stewart Pinkerton wrote:
> Rick Stadelmaier <rick_e...@my-deja.com> writes:
>
> >> > I'm note so sure it's the sustained bias plateau
> >> >operation, as if you look at idle current of, say a KSA 250, it's
> >> >clear that not withstanding the fact that Krell claims it's a pure
> >> >class A amp, it can not be, but rather is an A/B amp that is
> >> >unusually high biased into class A.
> >>
> >> It *is* a class A amp up to 250 watts into 8 ohms, which is its rated
> >> output. At lower impedances, it is of course class AB, as is true for
> >> any other class A power amp.
> >
> >It is most certainly *not* class A up to 250 watts.
> >If you do the math, you will find this to be impossible.
>
>
> Here come da math!
>
> Power consumption of the KSA250 at idle is rated at 120 volts, 12
> amps. This is 1,440 watts. A class-A push-pull amplifier has a
> theoretical maximum efficiency of 50%, typically more like 35%. Now,
> 1440 x 0.35 = 504, which just happens to be twice 250 watts for this
> stereo amplifier.
>
> Care to explain why this is 'impossible'?
--
BEARlabs
Thanks so much for "raising" my little business to the level of being
in " competition" with Krell! :- )
You do not have to give any weight whatsoever to my opinions - others
can form their own opinions of what I have to say.
But, as I said, they are rather different topologies, and do not
sound the same at all - or do you think that they DO sound the same??
Would you share that with us??
Thanks in advance,
_-_-
Stewart Pinkerton wrote:
> BEARlabs <bear...@coollink.net> writes:
>
> Regarding KSA and FPB series Krell amps:
>
> >IMHO, neither is a particularly clean, nor neutral amplifier. Neither
> >is technically superb, but both will dump huge amounts of voltage and
> >current into a load.
>
> OTOH Randy, what weight should one give to completely unsubstantiated
> opinions from a competitor?
--
Francois Yves Le Gal
wrote:
>Yes, but more to do with standard wall outlets not supplying enough
>power.
That's true in the US of A, or others 100 to 117 V countries, where a
standard wall outlet is only dimensioned for 13 A, thus limiting
total power consumption to 1.5 KVA or so.
But not in Europe or Austrasia, whre mains is at 210 to 240 V. The
same 13 A wall outlet is able to deliver more than 3 KVA.
And that's why a number of North American audiophiles have elected to
go 230 V dual phase (is it dual or dual floating?) in order to get a
better mains power delivery.
BEARlabs
phase.
Industrial clients can get 440 THREE Phase, and the related 220v 3
phase.
There are also higher voltages available to industrial users.
FYI... :- )
_-_-
--
Stewart Pinkerton
>On 21 Dec 2000 10:31:19 -0600, Rick Stadelmaier <equ...@pip.com.au>
>wrote:
>
>>Yes, but more to do with standard wall outlets not supplying enough
>>power.
>
>That's true in the US of A, or others 100 to 117 V countries, where a
>standard wall outlet is only dimensioned for 13 A, thus limiting
>total power consumption to 1.5 KVA or so.
US & Canada standard is 20 amps, and no one has a 100 volt supply.
>But not in Europe or Austrasia, whre mains is at 210 to 240 V. The
>same 13 A wall outlet is able to deliver more than 3 KVA.
>
>And that's why a number of North American audiophiles have elected to
>go 230 V dual phase (is it dual or dual floating?) in order to get a
>better mains power delivery.
It's split phase about a common return, and is available in the
kitchens of most American homes, so rerouting to the listening room is
a straightforward exercise.
Rick Stadelmaier
> >
> >to 60 or 80 W on 8 Ohms, no more.
>
> 250 watts into 8 ohms, as a simple check on its power consumption at
> idle (close to 1.5kW) will show.
As I already stated, Stewart, do the math and you will find otherwise.
To help you out, you would need over 3KW from your wall outlet to do
this.
> >>If you do the math, you will find this to be impossible.
> >
> >Well, it's possible, but not with the power supplies, transistors and
> >heatsinks used. A 250 W pure class A amp would need at least a 1 KW
> >power supply and yards and yards of heat sinks.
>
> This is sheer ignorance of the basic technical details of one of the
> finest power amplifiers ever made. In point of *fact*, the KSA 250 has
> a 5kW power supply (it's rated to output 2kW per channel *continuous*
> into 1 ohm), while its huge heatsinks are rather more than a yard long
> and very sharp-edged - this is not an amplifier to be handled easily!
> It also weighs 65kg.
This is all nice and well, though you must realise that a standard wall
outlet will not supply this much power.
End of story.
Once again, please do the math.
Rick.
Rick Stadelmaier
Equinox Audio
http://www.equinoxaudio.com.au
equ...@pip.com.au
Sydney, Australia
Stewart Pinkerton
>Gee Stew,
>
>Thanks so much for "raising" my little business to the level of being
>in " competition" with Krell! :- )
You're welcome. OTOH, Yugo is in competition with Mercedes...... :-)
>You do not have to give any weight whatsoever to my opinions - others
>can form their own opinions of what I have to say.
Quite so, but can your opinions be regarded as impartial?
>But, as I said, they are rather different topologies, and do not
>sound the same at all - or do you think that they DO sound the same??
Above a fairly uncritical lower limit, and assuming a load
sufficiently benign as to avoid current limiting, yes amps is mostly
amps unless they is designed to sound 'different'. No one has yet
shown *proof* that this is not the case.
>Would you share that with us??
Merry Christmas!
Stewart Pinkerton
>I can't be 100% sure of this, since I have never seen an actual
>full schematic of the KSA or Reference series of that era, but it
>seems to me that there is a "trick" employed in the bias circuit.
No trick to the earlier KSA series, they are 'brute force' fixed bias
designs!
>Actually, having never had one *here* on my bench to test, I
>can not be sure on that basis either - that would tell me if my
>idea is correct or not.
The KSA 250 draws 12 amps at idle from a 120 volt line - I'm sure you
can do the math! :-)
>I think this is why the KSA appears to play louder than an amp
>of supposedly equal power - at least this has been my experience.
Oh sure, they'll drive a rusty nail without a shrug..........
Stewart Pinkerton
>> >It is most certainly *not* class A up to 250 watts.
>>
>> I would concur here. This Krell model looks like a solid class A up
>> to 60 or 80 W on 8 Ohms, no more.
>
>Somewhere around that, yes.
Lots more than that, a full 250 watts in *fact*. Where are you getting
figures that suggest otherwise?
>> >If you do the math, you will find this to be impossible.
>>
>> Well, it's possible, but not with the power supplies, transistors and
>> heatsinks used. A 250 W pure class A amp would need at least a 1 KW
>> power supply and yards and yards of heat sinks.
As noted elsewhere, Francois is totally incorrect here, as the KSA 250
has at least *5 kW* power supplies and the most massive heat sinks
I've ever seen, well over a yard long if you count both sides of the
22" long amplifier, and if you can lift its 65kg mass!
>Yes, but more to do with standard wall outlets not supplying enough
>power.
The KSA250 draws 12 amps from a 120 volt rail, that's easily within
the rating of a wall socket, which is conventionally 20 amps.
Stereophi...@compuserve.com
> >If you do the math, you will find this to be impossible.
>
> Here come da math!
>
> Power consumption of the KSA250 at idle is rated at 120 volts, 12
> amps. This is 1,440 watts. A class-A push-pull amplifier has a
> theoretical maximum efficiency of 50%, typically more like 35%. Now,
> 1440 x 0.35 = 504, which just happens to be twice 250 watts for this
> stereo amplifier.
>
> Care to explain why this is 'impossible'?
I suspect the specified power consumption is incorrect. I still have a
KSA-250, so next time I get it out of storage, I'll check its actual
consumption. Its output stage bias current, however, is below that of a
true 250W/8 ohm class-A design.
The Krell KSA-250's rated output of 250W per channel into 8 ohms implies
a standing bias current of 3.95A per channel---square root of 250W/(2 x
8 ohms)---if all this power is to be delivered into 8 ohms with the
output stage running in class-A. The amplifier has the emitters of its
output-stage transistors loaded with series resistors of nominal 1 ohm
value. However, when I measured the KSA-250 for the Stereophile review
in January 1991, I found the average voltage drop across these emitter
resistors was 110.5mV, implying a standing bias for each complementary
pair of 110.5mA. As there are 12 pairs of output transistors per
channel, the total bias current was 1.33A. This will give a maximum
power for true class-A operation into 8 ohms of 28.5W rather than 250W.
By contrast, if I remember correctly, the standing bias of the KSA-50 I
purchased in 1983 (still doing sterling service for my speaker
measurements) had an output stage bias current of 1.8A.
When I discussed this with Krell's Dan D'Agostino, he confirmed this
figure. He had found that a bias current of 3.95A was impractical and
that backing off the bias to the measured figure didn't change the sound
quality but did drastically lower the wasted heat!
--
John Atkinson
Editor, Stereophile
Sent via Deja.com
http://www.deja.com/
Stewart Pinkerton
>In article <3a423...@corp.newsfeeds.com>,
> pat...@popmail.dircon.co.uk wrote:
>> Rick Stadelmaier <rick_e...@my-deja.com> writes:
>> >It is most certainly *not* class A up to 250 watts.
>> >If you do the math, you will find this to be impossible.
>>
>> Here come da math!
>>
>> Power consumption of the KSA250 at idle is rated at 120 volts, 12
>> amps. This is 1,440 watts. A class-A push-pull amplifier has a
>> theoretical maximum efficiency of 50%, typically more like 35%. Now,
>> 1440 x 0.35 = 504, which just happens to be twice 250 watts for this
>> stereo amplifier.
>>
>> Care to explain why this is 'impossible'?
>
>I suspect the specified power consumption is incorrect. I still have a
>KSA-250, so next time I get it out of storage, I'll check its actual
>consumption. Its output stage bias current, however, is below that of a
>true 250W/8 ohm class-A design.
It would certainly be interesting to know if this amplifier was in
fact the start of the slippery slope into class AB (despite the
claimed current drain), since the immediately preceding KSA-80 was
certainly a true class A amplfier - and accordingly hot to touch!
>The Krell KSA-250's rated output of 250W per channel into 8 ohms implies
>a standing bias current of 3.95A per channel---square root of 250W/(2 x
>8 ohms)---if all this power is to be delivered into 8 ohms with the
>output stage running in class-A. The amplifier has the emitters of its
>output-stage transistors loaded with series resistors of nominal 1 ohm
>value. However, when I measured the KSA-250 for the Stereophile review
>in January 1991, I found the average voltage drop across these emitter
>resistors was 110.5mV, implying a standing bias for each complementary
>pair of 110.5mA. As there are 12 pairs of output transistors per
>channel, the total bias current was 1.33A. This will give a maximum
>power for true class-A operation into 8 ohms of 28.5W rather than 250W.
>
>By contrast, if I remember correctly, the standing bias of the KSA-50 I
>purchased in 1983 (still doing sterling service for my speaker
>measurements) had an output stage bias current of 1.8A.
Yes, that gels with my KSA-50 mkII figures and indicates true class A
operation up to rated power.
>When I discussed this with Krell's Dan D'Agostino, he confirmed this
>figure. He had found that a bias current of 3.95A was impractical and
>that backing off the bias to the measured figure didn't change the sound
>quality but did drastically lower the wasted heat!
Hmmmmmm. Interesting. If this is so, then Krell were quite simply
lying in their brochure, which clearly states that the amplifier is a
true class A device and draws 12 amps.
dco...@cix.compulink.co.uk
earlier KSA 250 amplifier.
I went today to a dealer to hear what a well set up system should sound
like, to establish a benchmark against which to calibrate what I am
hearing.
The system auditioned consisted of
- a Meridian 508 CD player like mine
- my own Meridian 502 preamp which I carried to the shop
- a Krell FPB 300: stereo rather than monoblocks, but should be similar
enough
- Wilson System 6: mine are the system 5s.
The connection between the CD and preamp was balanced, but that between
the preamp and the power amp was single ended (though it both units will
take balanced). This mimics my setup.
We played a disc of the Lindsay String Quartet playing Haydn, recorded
just a couple of hundred yards away in London's Wigmore Hall at a concert
I attended; I've sat through several cycles of various complete quartet
cycles by them in that hall and have a clear idea of what I think it
should sound like. Other records chosen were the Polish Jewish band
Kroke's live concert of earlier this year, and Vladimir Horowitz's last
Carnergie Hall concert.
At the outset the same lifelessness was evident. All the instruments in
the Haydn sounding of roughly equal weight; but anyone who knows the
Lindsays understands that the leader, Peter Cropper, has a musical
personality that is completely dominant, and an astringent tone that sets
him apart from the others. That didn't come through at all. It sounded
like a glorified PA system rather than a musical machine.
I explained this to the dealer, and my reaction led him to change the
cable from the CD to the preamp. That made a difference, but not enough.
A further cable change, to one by Nordost, called Red something, gave
pretty much the sound I was looking to hear. A further change, to a more
expensive cable, over did things and made everything sound thin.
Then we tried puttting a DCS Delius A/D converter between the CD and the
preamp. I could hear perhaps a slight difference but not one I would pay
£8500 for.
Finally we replaced all the Meridian gear with Krell's KPS 25i, which is a
CD, converter and preamp all in one box. The difference was staggering,
on a completely different plane. The sound had was creamy smooth and at
the same time detailed, and had a depth (in terms of a third dimension)
that was more convincing.
Playing the Meridian 508 through the Krell's preamp showed that the
differences were largely but not completely due to the 502 preamp.
This is all a long winded way of saying that those who have suggested that
the old system happened by chance to be well balanced, and that cables
might be the route to rebalancing it, look like being right. Next step is
to experiment at home.
The questions that are in my mind now have changed.
1 Can I get the equipment I now have to perform better with the new
amplifiers than with the old? Overall, with the exception of the Krell
front end which made it miles better, I feel that the cable changes got
the system to sound nearly as good as I had with the KSA250, but no
better. If that's all we can manage I might as well trade back down again
and release the cash invested in amplifier.
2 I wonder what was special about the KSA 250 that made it work so
well with what I have, and what about the FPB 250 makes it necessary to
change items well upstream of it in the system.
3 Isn't it striking that cables can make more difference than the
electronic parts? I'm actually very suspicious about this. I'd
understand if there was a clear pecking order, with more expensive cables
making a predictable improvement over cheaper ones. But having to mix and
match them in a non-scientific way that varies from machine to machine
(this cable works with this amplifier but you need something quite
different with that amplifer) means that they are in effect the tone
controls we chucked out in the 1970s.
4 Is there a way to get the extra performance of the KPS 25 without
paying the cost in terms of money and inconvenience? It's bulky, ugly,
and has no matching tuner. (The Meridian kit is the best I know of which
includes a tuner which can be controlled by a single neat remote. I wish
there was a cost no object preamp in its product line.)
Finally, since others in the market for an amplifier may come looking
through archives of these discussions, I'd better note that on the
evidence of the sound I heard today, I no longer believe that the FPB
series can't be made to sound good. I just hope I can get it to do so for
me.
BEARlabs
> BEARlabs <bear...@coollink.net> writes:
>
> >Gee Stew,
> >
> >Thanks so much for "raising" my little business to the level of being
> >in " competition" with Krell! :- )
>
> You're welcome. OTOH, Yugo is in competition with Mercedes...... :-)
>
<snip>
>
>
> >But, as I said, they are rather different topologies, and do not
> >sound the same at all - or do you think that they DO sound the same??
>
> Above a fairly uncritical lower limit, and assuming a load
> sufficiently benign as to avoid current limiting, yes amps is mostly
> amps unless they is designed to sound 'different'. No one has yet
> shown *proof* that this is not the case.
I disagree with this theory - and if anyone would like to collaborate
on doing such a blind test experiment within the NYC/Albany/Boston
triangle (read: time, effort, money) I would be pleased to oversee
the technical set up and design. I am confident that we could put
this silly idea that amps all sound the same to bed without dinner,
in short order. To me this is a no brainer.
On the other hand, it is possible to find amps that DO sound almost
indestinguishable - but there are fewer of those that are "good"
(leave that definition for another day) than the LARGE group that are
so colored or grainy as to be easy to hear when compared to the few
that are "good".
In other words, I am confident that it would be trivial for DBT
listeners to hear the diff between a "good" amp and a KSA250 (for
example), or a Bryston (for example)... trivial. Between a KSA 250
and a KSA100, I dunno.
Any white knights got game??
_-_-
>
>
> >Would you share that with us??
>
> Merry Christmas!
--
_-_- BEAR Labs
"Custom Handcrafted Audio Components & Cables"
Notice: "bear...@coollink.net" is extinct as of Jan 5,2001 -
temp email after JAN 5 will be bear...@Netzero.net
BEARlabs
> BEARlabs <bear...@coollink.net> writes:
>
> >I can't be 100% sure of this, since I have never seen an actual
> >full schematic of the KSA or Reference series of that era, but it
> >seems to me that there is a "trick" employed in the bias circuit.
>
> No trick to the earlier KSA series, they are 'brute force' fixed bias
> designs!
So you say - I have a segment of what is supposedly a similar design
by John Syder (Snyder??) who I believe was the main designer for the
KSA series, and it is not at all the usual VBE bias circuit at all.
I am not sure that it is fixed bias at all. I have a suspicion that
the bias drops with drive, increasing the effective swing... thus the
odd dynamic in the bass, and the extra peak output.
Anyone got a schematic to prove me wrong?? :- )
[quoted text deleted -- deb]
--
_-_- BEAR Labs
"Custom Handcrafted Audio Components & Cables"
Notice: "bear...@coollink.net" is extinct as of Jan 5,2001 -
Stereophi...@compuserve.com
pat...@popmail.dircon.co.uk wrote:
> Stereophi...@compuserve.com writes:
> >When I discussed this with Krell's Dan D'Agostino, he confirmed this
> >figure. He had found that a bias current of 3.95A was impractical and
> >that backing off the bias to the measured figure didn't change the
> >sound quality but did drastically lower the wasted heat!
>
> Hmmmmmm. Interesting. If this is so, then Krell were quite simply
> lying in their brochure, which clearly states that the amplifier is a
> true class A device and draws 12 amps.
In talking to Dan, I got the impression that the decision to drop the
standing bias current to a more sensible level was made at the last
minute, after the product literature had been printed. It doesn't
stop the '250 from being one of the best-sounding Krells, in my
opinion, particularly in the bass.
Stewart Pinkerton
>Stewart Pinkerton wrote:
>>
>> Francois Yves Le Gal <fle...@free.fr> writes:
>>
>> >On 19 Dec 2000 22:15:00 GMT, Rick Stadelmaier <rick_e...@my-deja.com>
>> >wrote:
>> >
>> >>It is most certainly *not* class A up to 250 watts.
>> >
>> >I would concur here. This Krell model looks like a solid class A up
>> >to 60 or 80 W on 8 Ohms, no more.
>>
>> This a totally incorrect statement. The KSA250 *is* pure class A up to
>> 250 watts into 8 ohms, as a simple check on its power consumption at
>> idle (close to 1.5kW) will show.
>
>As I already stated, Stewart, do the math and you will find otherwise.
>To help you out, you would need over 3KW from your wall outlet to do
>this.
I've already demonstrated the math, maybe you missed that post?
Certainly, your own quoted figure is out by 100%! To obtain class A
operation up to 250 watts into 8 ohms, you need typically 700 watts of
quiescent power consumption, since the theoretical maximum efficiency
is 50% but typical designs are more like 35%. Given the unusually high
power ratings of the Krell KSA 150/250, their efficiency would be
expected to be quite high, since the fixed power losses at low voltage
are a smaller percentage of maximum power. Hence, the 12 amps at 120
volts, which is the rated idle consumption of the KSA 250, is
perfectly adequate to ensure true class A operation up to 250 watts
per channel into 8 ohms. This isn't exactly rocket science!
Rumour has it that Krell may not actually have applied the required
bias to production units, but this changes neither their claims nor
the attendant numbers.
>> >>If you do the math, you will find this to be impossible.
>> >
>> >Well, it's possible, but not with the power supplies, transistors and
>> >heatsinks used. A 250 W pure class A amp would need at least a 1 KW
>> >power supply and yards and yards of heat sinks.
>>
>> This is sheer ignorance of the basic technical details of one of the
>> finest power amplifiers ever made. In point of *fact*, the KSA 250 has
>> a 5kW power supply (it's rated to output 2kW per channel *continuous*
>> into 1 ohm), while its huge heatsinks are rather more than a yard long
>> and very sharp-edged - this is not an amplifier to be handled easily!
>> It also weighs 65kg.
>
>This is all nice and well, though you must realise that a standard wall
>outlet will not supply this much power.
So? You think that someone prepared to buy an amp capable of
outputting 4kW is incapable of hiring an electrician to provide the
wiring for an adequate supply? Of course, it's not even an issue in
Europe with more efficient 230 volt line power, where even a standard
domestic ring main will deliver 30 amps with a suitable connector
fitted, and kitchen supplies are rated for 60 amps, or 13.8kW from a
single line.
>End of story.
Hardly....
>Once again, please do the math.
You might want to do this yourself, correctly this time......
Stewart Pinkerton
>More on Krell's FPB250 monoblocks which I reported liking less than the
>earlier KSA 250 amplifier.
>
>I went today to a dealer to hear what a well set up system should sound
>like, to establish a benchmark against which to calibrate what I am
>hearing.
>
>The system auditioned consisted of
>- a Meridian 508 CD player like mine
>- my own Meridian 502 preamp which I carried to the shop
>- a Krell FPB 300: stereo rather than monoblocks, but should be similar enough
>- Wilson System 6: mine are the system 5s.
Right, so we're in a different room with different speakers.
<snip lots of subjective impressions>
>Finally we replaced all the Meridian gear with Krell's KPS 25i, which is a
>CD, converter and preamp all in one box. The difference was staggering,
>on a completely different plane. The sound had was creamy smooth and at
>the same time detailed, and had a depth (in terms of a third dimension)
>that was more convincing.
Right, so we've moved to a single-box player with everything running
off one master clock, and no separate preamp.
>This is all a long winded way of saying that those who have suggested that
>the old system happened by chance to be well balanced, and that cables
>might be the route to rebalancing it, look like being right.
Hmmm. You think cables actually matter in this context?
>1 Can I get the equipment I now have to perform better with the new
>amplifiers than with the old? Overall, with the exception of the Krell
>front end which made it miles better, I feel that the cable changes got
>the system to sound nearly as good as I had with the KSA250, but no
>better. If that's all we can manage I might as well trade back down again
>and release the cash invested in amplifier.
Quite so. Use a top-quality one-box player and perhaps a passive
preamp.
>2 I wonder what was special about the KSA 250 that made it work so
>well with what I have, and what about the FPB 250 makes it necessary to
>change items well upstream of it in the system.
Nothing, I suggest that the amps are a very minor part of the
differences here.
>3 Isn't it striking that cables can make more difference than the
>electronic parts? I'm actually very suspicious about this.
Quite right too! Consider the massive changes you've made elsewhere in
the system......
>4 Is there a way to get the extra performance of the KPS 25 without
>paying the cost in terms of money and inconvenience?
Try an Arcam CD-23 with a good passive controller placed close to the
power amp.
> It's bulky, ugly,
>and has no matching tuner. (The Meridian kit is the best I know of which
>includes a tuner which can be controlled by a single neat remote. I wish
>there was a cost no object preamp in its product line.)
I believe it's called the 800 series, but is mostly intended to work
with Meridians own digital input fully active speakers.
Basically, with the amount of money that's swilling around here, I
think you should take the time to run some *controlled* listening
tests under double-blind conditions, so you have some idea of what you
can *really* hear, as opposed to what's just wishful thinking and
dealer bullshit.
Stewart Pinkerton
>In talking to Dan, I got the impression that the decision to drop the
>standing bias current to a more sensible level was made at the last
>minute, after the product literature had been printed. It doesn't
>stop the '250 from being one of the best-sounding Krells, in my
>opinion, particularly in the bass.
Fair enough. Regardless of technical minutiae, and the exact extent of
the true class A operational envelope, I do still regard the KSA 250
as one of the best amps ever made, by anyone.
Stewart Pinkerton
>Stewart Pinkerton wrote:
>
>> BEARlabs <bear...@coollink.net> writes:
>> >But, as I said, they are rather different topologies, and do not
>> >sound the same at all - or do you think that they DO sound the same??
>>
>> Above a fairly uncritical lower limit, and assuming a load
>> sufficiently benign as to avoid current limiting, yes amps is mostly
>> amps unless they is designed to sound 'different'. No one has yet
>> shown *proof* that this is not the case.
>
>I disagree with this theory
It's not a theory, it's a statement of observed fact at this time, as
noted above.
> - and if anyone would like to collaborate
>on doing such a blind test experiment within the NYC/Albany/Boston
>triangle (read: time, effort, money) I would be pleased to oversee
>the technical set up and design. I am confident that we could put
>this silly idea that amps all sound the same to bed without dinner,
>in short order. To me this is a no brainer.
Agreed it's a no brainer, but I suspect that we're approaching the
subject from different angles! :-)
BTW, no one has *ever* said that *all* amps sound the same, this is a
perennial strawman that you and others insist on raising to obscure
the issue. What *has* been said (and you even *quoted* it above!), is
that "above a fairly uncritical lower limit, and assuming a load
sufficiently benign as to avoid current limiting, yes amps is mostly
amps unless they is designed to sound 'different'. No one has yet
shown *proof* that this is not the case."
This statement stands.
>On the other hand, it is possible to find amps that DO sound almost
>indestinguishable - but there are fewer of those that are "good"
>(leave that definition for another day) than the LARGE group that are
>so colored or grainy as to be easy to hear when compared to the few
>that are "good".
>In other words, I am confident that it would be trivial for DBT
>listeners to hear the diff between a "good" amp and a KSA250 (for
>example), or a Bryston (for example)... trivial. Between a KSA 250
>and a KSA100, I dunno.
I'm certainly confident that if any amp sounds different from a KSA250
(or Bryston 4B ST) under controlled conditions, then that can only be
because it is decidedly *not* a good amp! Do your Bear Labs amps sound
'different', Randy? :-)
We have of course heard these expressions of confidence on many
previous occasions - but always *before* the DBTs, never afterwards
(until the revisionism starts, at least........). Let's hope this
exercise for the new Millennium will prove different.
Rick Stadelmaier
otherwise.
> >To help you out, you would need over 3KW from your wall outlet to do
> >this.
>
> I've already demonstrated the math, maybe you missed that post?
> Certainly, your own quoted figure is out by 100%! To obtain class A
> operation up to 250 watts into 8 ohms, you need typically 700 watts of
> quiescent power consumption, since the theoretical maximum efficiency
> is 50% but typical designs are more like 35%. Given the unusually high
> power ratings of the Krell KSA 150/250, their efficiency would be
> expected to be quite high, since the fixed power losses at low voltage
> are a smaller percentage of maximum power. Hence, the 12 amps at 120
> volts, which is the rated idle consumption of the KSA 250, is
> perfectly adequate to ensure true class A operation up to 250 watts
> per channel into 8 ohms. This isn't exactly rocket science!
Then why did you get it wrong?
If the amplifier produces 250 watts RMS into 8 ohms it will need (at
minimum) + and - 75V rail voltages. The maths then works out to be
7.91 x (75 + 75) = 1186.5 watts dissipation per channel, or near
enough to 2.4 KW for stereo.
That assumes 100% efficiency for every part of the amplifier,
rectifiers, transformers etc - in reality over 3KW would be consumed
> Rumour has it that Krell may not actually have applied the required
> bias to production units, but this changes neither their claims nor
> the attendant numbers.
I wonder why Stewart? Is this not what I said all along?
> >This is all nice and well, though you must realise that a standard wall
> >outlet will not supply this much power.
>
> So? You think that someone prepared to buy an amp capable of
> outputting 4kW is incapable of hiring an electrician to provide the
> wiring for an adequate supply? Of course, it's not even an issue in
> Europe with more efficient 230 volt line power, where even a standard
> domestic ring main will deliver 30 amps with a suitable connector
> fitted, and kitchen supplies are rated for 60 amps, or 13.8kW from a
> single line.
That may be true, though this would seem silly if the amp is produced
to run on a standard outlet, but to perhaps gain maximum performance,
needs a rewire.
BTW, you quoted 4KW this time and 5KW in a previous post, which is
it?
> >Once again, please do the math.
>
> You might want to do this yourself, correctly this time......
I did.
Regardless of all the quoted figures, the amp is quite good, _not_ as
good as you say, IMHO, but the fact remains it is _not_ 250w full
class A.
This is all I have to say.
Rick.
Equinox Audio
http://www.equinoxaudio.com.au
equ...@pip.com.au
Sent via Deja.com
http://www.deja.com/
Stewart Pinkerton
>> >As I already stated, Stewart, do the math and you will find otherwise.
>> >To help you out, you would need over 3KW from your wall outlet to do
>> >this.
>>
>> I've already demonstrated the math, maybe you missed that post?
>> Certainly, your own quoted figure is out by 100%! To obtain class A
>> operation up to 250 watts into 8 ohms, you need typically 700 watts of
>> quiescent power consumption, since the theoretical maximum efficiency
>> is 50% but typical designs are more like 35%. Given the unusually high
>> power ratings of the Krell KSA 150/250, their efficiency would be
>> expected to be quite high, since the fixed power losses at low voltage
>> are a smaller percentage of maximum power. Hence, the 12 amps at 120
>> volts, which is the rated idle consumption of the KSA 250, is
>> perfectly adequate to ensure true class A operation up to 250 watts
>> per channel into 8 ohms. This isn't exactly rocket science!
>
>Then why did you get it wrong?
>If the amplifier produces 250 watts RMS into 8 ohms it will need (at
>minimum) + and - 75V rail voltages. The maths then works out to be
>7.91 x (75 + 75) = 1186.5 watts dissipation per channel, or near
>enough to 2.4 KW for stereo.
>That assumes 100% efficiency for every part of the amplifier,
>rectifiers, transformers etc - in reality over 3KW would be consumed
Utter nonsense! 250 watts into 8 ohms requires 44.7 Vrms, or 63 V
peak, and class A operation requires a bias current of half the peak
value, which is 63/8/2 = 3.95 amps. Your basic mistake is in assuming
*twice* the actual bias current required. Please learn the basics
before accusing others of error.
BTW, the transformers and rectifiers are *much* more efficient than
you assume above, better than 95% in fact, while you should be able to
achieve 63 V peak with around 70 volt power rails in a bipolar amp
like the big Krell. Yes, it does in fact have higher rail voltages,
but then it actually puts out around 320 watts into 8 ohms in order to
provide its rated 2kW into 1 ohm.
>> Rumour has it that Krell may not actually have applied the required
>> bias to production units, but this changes neither their claims nor
>> the attendant numbers.
>
>I wonder why Stewart? Is this not what I said all along?
No, you kept claiming that it not only wasn't, but couldn't be class A
at 250 watts into 8 ohms. This is simply not true, as I have
demonstrated ad nauseam.
>> >This is all nice and well, though you must realise that a standard wall
>> >outlet will not supply this much power.
>>
>> So? You think that someone prepared to buy an amp capable of
>> outputting 4kW is incapable of hiring an electrician to provide the
>> wiring for an adequate supply? Of course, it's not even an issue in
>> Europe with more efficient 230 volt line power, where even a standard
>> domestic ring main will deliver 30 amps with a suitable connector
>> fitted, and kitchen supplies are rated for 60 amps, or 13.8kW from a
>> single line.
>
>That may be true, though this would seem silly if the amp is produced
>to run on a standard outlet, but to perhaps gain maximum performance,
>needs a rewire.
>
>BTW, you quoted 4KW this time and 5KW in a previous post, which is
>it?
Please *read* what is posted. The rated *output* of the amp is 4kW,
which requires 5kW *power supplies*.
>> >Once again, please do the math.
>>
>> You might want to do this yourself, correctly this time......
>
>I did.
As noted above, you were out by more than 100%.........
>Regardless of all the quoted figures, the amp is quite good, _not_ as
>good as you say, IMHO, but the fact remains it is _not_ 250w full
>class A.
Maybe, maybe not, but it is certainly rated as such by Krell, and has
adequate power supplies for this to be true. We could of course argue
endlessly as to the *value* of true class A operation, but that's a
whole different thread!