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

@geoffkait 

Hmmm. Interesting. Perhaps there isn't as much difference between violins? What do I know? I'm only a trumpet player. ;^)

That doesn't mean that musicians are unable to tell the difference between other instruments (as in my Oscar Peterson example).

nordicnorm
@geoffkait

Hmmm. Interesting. Perhaps there isn’t as much difference between violins? What do I know? I’m only a trumpet player. ;^)

>>>>>>I actually think it doesn’t necessarily mean that at all. I think there may very well be significant differences between/among good violins that trained musicians cannot distinguish, or cannot distinguish in a test, in particular a controlled blind test. Some people don’t test well. 😀 My evidence: exhibit no. 1 is that some of the worst sounding audio systems I ever heard were those of musicians. Now, all you musicians out there, please don't send me a bunch of angry emails, I'm sure some of you can hear OK. 😀

nordicnorm
That doesn’t mean that musicians are unable to tell the difference between other instruments (as in my Oscar Peterson example).

>>>>>Actually, I suspect it might mean that musicians may not be able to tell differences between other instruments. It’s the process or perhaps the test subjects themselves that’s flawed somehow. Can trained musicians tell the difference between cables? Power cords? Fuses? Can you?

Notwithstanding my personally-held belief that high end stuff sounds better to me, I am willing to concede that some of the claimed superiority I (we) claim to hear in amplifiers or perhaps cables as well is due to the fact that the products we are attempting to A/B are not level matched to within a very tight tolerance.  There are just too many people that seem to fail these comparison tests when the products are level matched to ignore the statistic totally.  I think. 

Damping factor of the Macs is said to be 12.
What, if any, difference in frequency response of my speakers should I hear due to the varying impedance curve?

@dentdog with that much feedback, none at all. OTOH, the fact that the amp runs feedback means it will *sound* a little brighter on top due to added trace amounts of higher ordered harmonic distortion. The emphasis is added on account of on the bench no change in frequency response would be seen.

What Ralph said

https://benchmarkmedia.com/blogs/application_notes/power-amplifiers-the-importance-of-the-first-watt

This explains why my amps are designed as Class A to 2/3 power. The switching distortion at high output is insignificant compared to everything else. However at very low levels switching distortion is audible (at least on test signals) - so it is preferable to be in Class A at low levels (of less than 1/10 of a watt)

The article confirms to me that only carefully designed listening tests at very low levels will lead to audible differences between well designed high quality power amplifiers. Alternatively, stressful loads or extreme power requirements would audibly differentiate the amplifier with better performance.