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......
Hi,
IT would appear that you prefer to repeat hearsay and mis-perceptions, compared to real information. There are too many to address all in one post, but I will try.
First, the current standard recommendations (including the US FTC) specify 1% THD as power limit. In the German DIN 45500 a distortion limit of 0.5% is set, however regardless of the FTC rules and DIN45500 we also often find maximum power stated at 10% THD.
In non of the standards and recommended practices is there a different limit for tube and solid state amplifiers.
Secondly, Tube Amplifiers generally use few stages with low gain and low or no feedback. This means they show relatively high measured THD at higher power and relatively high output impedances. This is not a direct result of using tubes but of circuit topology.
If use two gain stages composed of Pentodes and the normal output stage we can achieve open loop gain levels comparable to those in Solid state amplifiers and it is easily possible to achieve equally low measured THD and Low Output impedance. This is rarely done for a variety of reasons, but it has been done and can be done.
Thirdly, as feedback levels are low, available input voltage ranges in the input device (tube) and open loop bandwidth are generally (if feedback is used at all) Tube Amplifiers are not normally slew rate limited in the way soliud state amplifiers and the mechanisms through which TIM is produced even if the amplifier is significantly below slewing are absent. Also absent in tubes are several classes of distortion unique to solid state devices.
Low Damping is just as the apparent higher distortion a result of the specific circuits employed and a not a result of using tubes as such, again, increasing feedback levels can reduce output impedance dramatically.
Fourth, limited bandwidth in the bass is again purely a result of specific design choices made in a specific amplifier. Using a large enough core for the output transformer (expensive) and enough feedback can create performance comparable to transistor amplifiers.
Fifth, another fundamental question is why high Damping Factor and low THD are considered important qualities as such, given the behaviour of real speakers (where electrical damping is limited by the voice coil DCR and distortion at rated power often reaches double figures)... This is a major topic in itself, however it is sufficient here to note that there is no credible research that supports lowering amplifiers HD and Output Impedance past levels that are easily attained by most tube and transistor amplifiers.
I cannot speak for others, but personally I am well familiar both with techniques needed to measure audio equipment and with the gear needed to do so. But I also understand how these measurements relate to the system a given device is employed in and how they relate to what people actually hear.
The persistent insistence on the important of measurements that have been illustrated as not being capable of giving meaningful information of the actual audible qualities (e.g. lower measured THD does not reliably correlate with lower audible distortion) and more, the representation that such insistence represents anything "scientific"; I find comical in a way that parallels how I find the behaviour of the peasants in the "She's a Witch" Skit in Monty Python's "Holy Grail" comical, even though it's more a tragedy than a comedy.
Ciao T
IT would appear that you prefer to repeat hearsay and mis-perceptions, compared to real information. There are too many to address all in one post, but I will try.
First, the current standard recommendations (including the US FTC) specify 1% THD as power limit. In the German DIN 45500 a distortion limit of 0.5% is set, however regardless of the FTC rules and DIN45500 we also often find maximum power stated at 10% THD.
In non of the standards and recommended practices is there a different limit for tube and solid state amplifiers.
Secondly, Tube Amplifiers generally use few stages with low gain and low or no feedback. This means they show relatively high measured THD at higher power and relatively high output impedances. This is not a direct result of using tubes but of circuit topology.
If use two gain stages composed of Pentodes and the normal output stage we can achieve open loop gain levels comparable to those in Solid state amplifiers and it is easily possible to achieve equally low measured THD and Low Output impedance. This is rarely done for a variety of reasons, but it has been done and can be done.
Thirdly, as feedback levels are low, available input voltage ranges in the input device (tube) and open loop bandwidth are generally (if feedback is used at all) Tube Amplifiers are not normally slew rate limited in the way soliud state amplifiers and the mechanisms through which TIM is produced even if the amplifier is significantly below slewing are absent. Also absent in tubes are several classes of distortion unique to solid state devices.
Low Damping is just as the apparent higher distortion a result of the specific circuits employed and a not a result of using tubes as such, again, increasing feedback levels can reduce output impedance dramatically.
Fourth, limited bandwidth in the bass is again purely a result of specific design choices made in a specific amplifier. Using a large enough core for the output transformer (expensive) and enough feedback can create performance comparable to transistor amplifiers.
Fifth, another fundamental question is why high Damping Factor and low THD are considered important qualities as such, given the behaviour of real speakers (where electrical damping is limited by the voice coil DCR and distortion at rated power often reaches double figures)... This is a major topic in itself, however it is sufficient here to note that there is no credible research that supports lowering amplifiers HD and Output Impedance past levels that are easily attained by most tube and transistor amplifiers.
I cannot speak for others, but personally I am well familiar both with techniques needed to measure audio equipment and with the gear needed to do so. But I also understand how these measurements relate to the system a given device is employed in and how they relate to what people actually hear.
The persistent insistence on the important of measurements that have been illustrated as not being capable of giving meaningful information of the actual audible qualities (e.g. lower measured THD does not reliably correlate with lower audible distortion) and more, the representation that such insistence represents anything "scientific"; I find comical in a way that parallels how I find the behaviour of the peasants in the "She's a Witch" Skit in Monty Python's "Holy Grail" comical, even though it's more a tragedy than a comedy.
Ciao T
Hi,
Just shows what is known, doesn't it? At least by you, that is. Known to me is this:
http://www.wolcottaudio.com/WA_Pres_specs.htm
To quote:
FREQUENCY RESPONSE @ 1 Watt 0 - .2 db 20 - 20 kHz
+/-0.5 db 3 Hz to >20 kHz; -3 db @ 65 kHz.
POWER OUTPUT
2 ohm load- 240 watts, 12 Hz to 20 kHz.
4 ohm - 280 watts, 16Hz to 30 kHz.
8 ohm load- 180 watts, 20 Hz to 30 kHz.
6 - 8 ohms, 350 - 400 Watts, 20 Hz - 30 kHz.
THD FULL POWER
Typical @ Rated Load Less than 0.01% midband
0.025% @ 20 Hz
0.1% - 0.2% Max @ 20kHz
IM: 60/7000 Hz, less than 0.02%.
TIM: Unmeasurable
SIGNAL TO NOISE RATIO: 95 - 100 db
DAMPING FACTOR: >500, 30-5000Hz
Then there was the Krohn Hite Amplifier designed by Dick Burwen...
Ciao T
Just shows what is known, doesn't it? At least by you, that is. Known to me is this:
http://www.wolcottaudio.com/WA_Pres_specs.htm
To quote:
FREQUENCY RESPONSE @ 1 Watt 0 - .2 db 20 - 20 kHz
+/-0.5 db 3 Hz to >20 kHz; -3 db @ 65 kHz.
POWER OUTPUT
2 ohm load- 240 watts, 12 Hz to 20 kHz.
4 ohm - 280 watts, 16Hz to 30 kHz.
8 ohm load- 180 watts, 20 Hz to 30 kHz.
6 - 8 ohms, 350 - 400 Watts, 20 Hz - 30 kHz.
THD FULL POWER
Typical @ Rated Load Less than 0.01% midband
0.025% @ 20 Hz
0.1% - 0.2% Max @ 20kHz
IM: 60/7000 Hz, less than 0.02%.
TIM: Unmeasurable
SIGNAL TO NOISE RATIO: 95 - 100 db
DAMPING FACTOR: >500, 30-5000Hz
Then there was the Krohn Hite Amplifier designed by Dick Burwen...
Ciao T
Hi,
Tubes alone make very poor compressors. You need certain pentodes and adjust the screengrid voltage to get a good compressor (Variable Mu). Even BJT's actually compress much better.
Speakers on the other hand make very good compressors all on their own, almost as good as magnetic tape saturation...
Ciao T
Tubes alone make very poor compressors. You need certain pentodes and adjust the screengrid voltage to get a good compressor (Variable Mu). Even BJT's actually compress much better.
Speakers on the other hand make very good compressors all on their own, almost as good as magnetic tape saturation...
Ciao T
Is this Hearsay...or mis-perceptions..?
Music Reference RM-200 Mk.II power amplifier Measurements | Stereophile.com
As did the original version of the Music Reference RM-200 amplifier, the Mk.II edition offers superb measured performance for a tubed design, particularly in terms of midband distortion and the ability to drive low impedances. And I remain impressed by the quality of its output transformers.—John Atkinson
Another : http://www.stereophile.com/content/conrad-johnson-lp125m-monoblock-power-amplifier-measurements
Conrad-Johnson's LP125M measures well for a traditional tube amplifier.—John Atkinson
Notice a theme ...? and please spare me the innuendo's , I'm not anti-tube, just trying to find where you are getting your numbers from ..
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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 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.
All I know, John Atkinson has pre-suppositions about amplifiers and their parameters. I would say similarly, John Atkinson shows superb knowledge for an author of a popular magazine. No offense, just completely equal analogy in expressions.
If low THD and high DF are not typical for best sounding amps, the proper conclusions would be, they are less significant than other parameters.
If low THD and high DF are not typical for best sounding amps, the proper conclusions would be, they are less significant than other parameters.
There are historically some good examples of this such as the Quad 405 that measures exceptional, but sounds average. If we were to believe the measurements alone and gone on our merry way- then the 405 should have sounded better.. but it did not And Pioneer technicians with their Legato Link appeared to temporarily abandon measurement in favor of listening. Were Pioneer naughty or had they stumbled upon something. Technology: LEGATO LINK CONVERSION PRO - KURO Projector
The benefit of measurement is quantifiable and repeatable result, The benefit of listening is to enjoy. Translating listening back to measurements where the two provide quantifiable result is the challenge. The ESL57 as a loudspeaker seemed to provide both good measurement - despite its awkward impedance and excellent listening. So it is possible. If we were to view the 57's impedance as poor, and try to find a better impedance curve - would we necessarily have a better sounding speaker ? Of course amplifier matching to the speaker answers some of this. But I think No, the 57 provided magnificent listening but its impedance measured all over the place... I am glad Peter Walker continued production and didn't stop production due to poor impedance, the 57 has proven as a huge success to everyone who has heard them .
Recent forum contributions in Solid State powering Op amps has touched on this as well where I have asserted that transistors for each polarity NPN arranged with collector as Vin, a resistor of 2K4 from collector to base and emitter feeding V+, and PNP arranged the same feeding V- of an op amp, offers much better spatial stereo information. Its an unconventional method of connecting transistors - but it sounds great.
Cheers / Chris
The benefit of measurement is quantifiable and repeatable result, The benefit of listening is to enjoy. Translating listening back to measurements where the two provide quantifiable result is the challenge. The ESL57 as a loudspeaker seemed to provide both good measurement - despite its awkward impedance and excellent listening. So it is possible. If we were to view the 57's impedance as poor, and try to find a better impedance curve - would we necessarily have a better sounding speaker ? Of course amplifier matching to the speaker answers some of this. But I think No, the 57 provided magnificent listening but its impedance measured all over the place... I am glad Peter Walker continued production and didn't stop production due to poor impedance, the 57 has proven as a huge success to everyone who has heard them .
Recent forum contributions in Solid State powering Op amps has touched on this as well where I have asserted that transistors for each polarity NPN arranged with collector as Vin, a resistor of 2K4 from collector to base and emitter feeding V+, and PNP arranged the same feeding V- of an op amp, offers much better spatial stereo information. Its an unconventional method of connecting transistors - but it sounds great.
Cheers / Chris
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Hi,
It is.
Really, I couldn't tell, TBH.
I measure, how else?
How do you get yours?
BTW, to repeat, i do not consider very low THD or very high damping factors relevant or beneficial, in the light of the whole system. However, I am familar with and have worked myself on tube designs that perform broadly comparable to solid state gear in these areas.
Ciao T
It is.
Really, I couldn't tell, TBH.
I measure, how else?
How do you get yours?
BTW, to repeat, i do not consider very low THD or very high damping factors relevant or beneficial, in the light of the whole system. However, I am familar with and have worked myself on tube designs that perform broadly comparable to solid state gear in these areas.
Ciao T
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.
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 !!!
Tube preamp THD 0.2% within band 5Hz - 500KHz (3dB)
amp THD 1% within band 7Hz - 350KHz (3dB)
Home page
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.
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 ..
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 ..
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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.
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.
For reference ....
Parasound Halo JC 1 monoblock power amplifier Measurements | Stereophile.com
I would suggest that listening test be done over, with better speakers ...
Parasound Halo JC 1 monoblock power amplifier Measurements | Stereophile.com
I would suggest that listening test be done over, with better speakers ...
Hi,
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
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
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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