Richard Clark $10,000 Amplifier Challenge - Why Couldn't Anyone Pass this Test??

@atmasphere

I am saying your entire argument is bunk, because the ideal audio amplifier is a voltage source, not a current source. In essence you are also arguing for amplifiers of TINY damping factor being ideal. Not supported by anyone but you.  In fact, the amplifier I quoted, has a damping factor of around 0.8.  That's about 400x worse than even a mediocre solid state amps.

Complementing the amplifier design, speakers are measured by the output vs. frequency based on constant input voltage. For your theory to be at all accurate, speakers would have to have flat power efficiency (input vs. output) and ....they don't! The power efficiency of almost all multi-way speakers varies tremendously based on frequency. The LAST thing on earth you want is a constant current amplifier, unless you want your output to look like your impedance curve.

If you are right, then man, 10 Ohms is too low. You should make amps with 30 or 50 ohms at the output, you would get even more ideal current sources! << hahahahah >>

You know, it is a real shame that you take this tack, because I actually think you have a lot of fans, and built good products, but I've gotten really tired of you constantly hammering the superiority of high output impedance amps as a feature based on false and misleading (that's your own phrase) statements you repeat over and over again.

Best,

E

Changing the subject entirely, Ralph, did they ever retire that Nobel for Patience?

Erik_Squires 5-15-2017

atmasphere:
I am saying your entire argument is bunk, because the ideal amplifier is a voltage source, not a current source.

I’ll have to disagree with you on this, Erik. The ideal amplifier is a voltage source if the speaker it is used with is designed to sound its best when driven by a voltage source. As Ralph indicated, many speakers are not designed that way. While some others (such as the Daedalus Ulysses I use) don’t particularly care about amplifier output impedance or voltage source behavior, as their own impedance is very flat. And of course many people get great results with tube amplifiers such as SETs that have output impedances similar to the output impedances of Ralph’s designs (e.g., 2 to 4 ohms or so for most models).

Also, as Ralph indicated the output impedances of his designs are not nearly high enough for them to be considered to be current sources.

Finally, as I said earlier in the thread, "the bottom line with respect to the tube-friendliness or lack thereof of the ESL57 is perhaps indicated by the fact that it was designed before solid state amps existed." Although admittedly my understanding is that many of the tube amps of that era did incorporate significant amounts of feedback, which in the case of those amplifiers brought them somewhat closer to behaving as voltage sources than many high quality modern tube designs.

Best regards,
-- Al

Hi Al,

There are flat impedance speakers out there, which is often accomplished with additional impedance normalizing circuits in the crossover. Certainly a niche.

In these cases it is rightfully argued that the output impedance of amplifiers will have negligible effect on the frequency response.

If this was Atma’s argument I would leave it alone. His repeated disinformation that the high output impedance is BETTER because it has constant power output regardless of impedance is nonsense. In no measurable case is it ever better. The measurements by SoundState and Stereophile are consistent. With "normal" speakers high impedance causes significant deviation from ideal.

Of course, buy what you like.

Best,


E

What Al said, plus

You know, it is a real shame that you take this tack, because I actually think you have a lot of fans, and built good products, but I've gotten really tired of you constantly hammering the superiority of high output impedance amps as a feature based on false and misleading (that's your own phrase) statements you repeat over and over again.

What is it that you're saying here? That I build good products, but - ? they aren't real or something? I'm sensing a contradiction here.

IMO you've been misreading what I've been writing.

I have qualms about **feedback**, not output impedance, as long as the low output impedance does not come with added higher ordered harmonics. And I can back my qualms up easily enough without going into the weeds. If you are not familiar with Norman Crowhurst, he is a well-known authority in the field of amplifier design. His books are likely a bit rare but the important ones are a free download from Pete Millet's site:
http://www.tubebooks.org/technical_books_online.htm

In fact I would love it if I could make the output impedance of our amps lower. The problem I have with solid state is that many semiconductors have a non-linear aspect about them that causes them to have higher ordered harmonics (at low levels, but as I pointed out earlier, the ear is very sensitive to that sort of thing) and hard clipping. The only devices that I have found that don't are the static induction transistors made by Sony. IMO They had a chance to really set the audio world forward, but in true Sony fashion (which is to come up with an innovation and then shoot themselves in the foot) failed to make a full complement of driver and voltage amplifier devices to go with their rather amazing output devices.

With such technology we could have had low distortion, zero feedback and low output impedance all at the same time!

For the most part, what I'm really hammering on is the simple fact that you can't seem to get low distortion **and** low output impedance at the same time. Now I do this in the face of the fact that many solid state amps **appear** to have very low distortion, but what research in the last 40 years has shown is that the ear has distortion on a curve of sorts; the lower ordered harmonics being unimportant to the ear and the higher ordered harmonics are really really important. I freely acknowledge that this flies in the face of the test and measurement regime, which I feel is outdated by research of the last 40-50 years.

Can you describe the sound of an amplifier by looking at its spec sheet? Most audiophiles can't; so why is there a spec sheet? The fact is most spec sheets are there to make the product look good on paper and have nothing to do with how the ear hears. That's a pretty good example of the Emperor's New Clothes...

Now if one is to say that the specs are the final arbiter, great, no worries. Have at it. But I feel that the ear, not the specs, is why we buy audio equipment and that equipment will sound better if the gear follows the rules of human hearing. 

Did you mention what your speaker brand is? I missed that bit.