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Old 26th December 2011, 06:05 AM   #151
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Quote:
Originally Posted by wahab View Post
It use likely the generic schematic of the AVR-XXX serie , as such ,
the most classical LIN you can imagine , differential + bootstrapped VAS + fast Darlingtons from SANKEN......
I've found schematic. It is actually 2-stage LTP with current mirror, no bootstrap, fast Sanken Darlingtons, smart HF compensation, Zeners in current limiting. Smart minimalist design.
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Old 26th December 2011, 06:44 AM   #152
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Originally Posted by john curl View Post
Let's get real, engineers! The ONLY way to get really low distortion is to use a lot of paralleled parts and most probably the most feedback that you can put in the circuit.
I have made amps that have very low distortion for test equipment, but I don't think they are optimum for audio, because of the extra complication of nested loops, and potential instability with difficult loads. Now that is MY opinion, and others here might have another opinion, and that is OK with me.
It is well known that vacuum tubes are the most linear (standing alone) than any other active device. Also, as Wavebourn stated, output transformers are usually necessary with tube power amplifiers, and they are always a compromise. Also, it is almost impossible to apply a great deal of negative feedback with both transformers and capacitor coupling, and so, tube amps are usually limited to 20-30dB in feedback, rather than 60-100dB that is possible with solid state.
Now, two tube amp designs with rather different specifications have been put up here. So what? One amp is obviously designed with more parts, and more expensive parts to get its specifications.
It is interesting that solid state amps rarely measure very well either, unless a good deal of negative feedback is used. Just look at the Ayre power amps in Sterephile. AND they are made to the highest standard that is practical and possible. Take it from me, I wish I could do some of the approaches that Charles Hansen uses.
I'm with you John, now all amps are built with some degee of NFB, so to say one measures better only because it takes more geritol than the other says what ? What are we looking for ?

My point was in response to tubes being able to bench press the same as SS amps, they don't, not on mere specs and since tubes have great linearity, why not more hybrid amps, it would make sense for tubes with output mosfets...

No transformers..! less NFB......sounds like a winner to me !!!
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Old 26th December 2011, 06:47 AM   #153
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Quote:
Originally Posted by a.wayne View Post
I'm not anti-tube, just trying to find where you are getting your numbers from ..
Tube preamp THD 0.2% within band 5Hz - 500KHz (3dB)
amp THD 1% within band 7Hz - 350KHz (3dB)
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IMHO major drawback of a solid-state amp it sounds either too warm or too cold too thin or too juicy too relax or too harsh ( I was owning gear from Carver, Nakamichi, Accuphase, Krell FPB ) when good tube stuff just do it right. Not sure if a bunch of feedbacks or higher input capacitance or thermal nonlinearity is the reason.

Anyway best sound is hieff speakers and pure class A amplification. For a class A design tubes are the best.
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Old 26th December 2011, 06:52 AM   #154
a.wayne is offline a.wayne  United States
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The Graff struggles a bit here too Boss....

Graaf GM 200 OTL power amplifier Measurements | Stereophile.com

Best sound is your sound ... always !!! IMHO SS amps suffer from thermal distortion, control this and there is no cold /thin/ sound ..

Last edited by a.wayne; 26th December 2011 at 06:56 AM.
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Old 26th December 2011, 07:07 AM   #155
a.wayne is offline a.wayne  United States
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Mr Hansen ...

Ayre MX-R monoblock power amplifier Measurements | Stereophile.com
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Old 26th December 2011, 07:21 AM   #156
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What must be understood, is that my JC-1 will run rings around the Ayre, measurement wise, because I use global negative feedback. Not because it makes the amp sound better, but because it makes the amp MEASURE better. Charles has beat me out in some listening tests with his amp, because his amp does NOT use global negative feedback, even though my amp is bigger and lower distortion.
Look at the JC-1 measurements and compare. This is WHY Charles and I tend to frown on negative feedback, IF we can get away from it.
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Old 26th December 2011, 07:45 AM   #157
a.wayne is offline a.wayne  United States
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For reference ....

Parasound Halo JC 1 monoblock power amplifier Measurements | Stereophile.com


I would suggest that listening test be done over, with better speakers ...
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Old 26th December 2011, 07:56 AM   #158
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Hi,

Quote:
Originally Posted by a.wayne View Post
My point was in response to tubes being able to bench press the same as SS amps, they don't, not on mere specs
I posted two examples of Tube Amplifiers with measured specifications that equal many high quality transistor amplifier, namely the Krohn Hite Laboratory Amplifier and the Wollcott Presence Range. The HK Citation II for all it's agae as well as many McIntosh Amplifiers also have specifications well comparable to many transistor amplifier.

The point however is that many Tube amplifiers are not designed and build to compete with transistor amplifiers on specifications, hence you do not find many tube amplifiers that have specifications comparable to Solid State Amplifiers THD and Damping factor.

Rather they are designed to outperform solid state amplifiers in subjective terms, with the artificial and meaningless specs of THD and Damping Factor assigned their proper importance.

In fact, one of the reasons why we see damping factor and THD elevated so much in importance is strictly down to advertising, not to actual, reliably demonstrable superiority of amplifiers with lower THD and high Damping factor.

The advertising race was given an early starting shot by Harold Leak who used to advertise his products as offering "point one" percent THD, mostly an advertising gimmick as his products did not really measure different from other generic amplifiers using Mullard Application note schematics, what was different was simply the level at which he measured this "point one" THD.

When in the 60's and 70's Transistor amplifiers dramatically failed to outperform even mediocre tube amplifiers on subjective sonic terms, the race started in earnest as it was not hard to create transistor amplifiers with more and more feedback and lower and lower THD and greater and greater damping factor. It did not make them any better in terms of sounding good, but it gave the marketing departments a great opportunity to paint tube amplifiers performing poorly.

Non of this gives any proof that lowering the amplifiers THD much below that of the speaker provides any audibly reduced distortion or any audible benefit. In fact any such claims can only be regarded as urban myth that require not even most casual scientific testing to be shown to be utterly absurd.

Equally, there is no proof that improving an amplifiers damping factor beyond a point where modifications of the attached speakers frequency response are kept below audibility provides any audible benefit and indeed, any such claims must be equally regarded as complete and utter bunkum.

I would give my honest opinion here of those who continue to perpetuate such bunk, such urban myth and baseless beliefs, however the moderators would likely take exception to such honestly, hence I shall leave things at this...

Ciao T
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Old 26th December 2011, 08:18 AM   #159
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Quote:
Originally Posted by a.wayne View Post
Best sound is your sound ... always !!!
No it is not quite right. I've heard audio better than mine but it's always a tradeoff between gear and habitability (WAF ). However I understand what experienced audiophile means by saying “once I had got this particular piece of equipment I’ve stop looking further”. Unfortunately I never met such solid state amp or preamp that I was completely satisfied with.

However I am seriously impressed by ultrasound ICs (OPA637, LM4702). I truly believe that solid state amps now are getting on a par with tube gear sonically, however ICs based only.

Anyway my original point that I mentioned earlier in the topic was about anechoic chamber that sound related measures are no good without. "Simulation load" measures are fake basically IMHO.

But real measures in anechoic chamber are expensive so only very few primarely HiEnd manufactures like McIntosh can afford them.
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Old 26th December 2011, 10:37 AM   #160
SY is offline SY  United States
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Quote:
Originally Posted by tvrgeek View Post
Er, yea. It is not linear either. Enter where the discussion splits to ccs vs cvs vs a resistor on the cathode.
That has zero to do with being a compressor.
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