Amp Specs esp. DampFactor : Citation, Adcom, etc.

I am sure that in future, the set of measurments will predict fully amplifier behaivor.

Today, however, many measurments are meaningless or obtained by using dubious techniques design to improve measurments results and not sound.

Today, there are very few measurments which can preedict accurately what to expect e.g. headroom, bandwidth, lowest impedance the amplifier is stable and may be a few more.
THD is not but distortion spectrum will tell me a lot.

At any rate, DF is the ratio of speaker input impedance to amplifier output impedance at given frequency (I think 100 Hz but not sure) and can be achived, as Kijanki said by using deep slow negative feedback. I saw amplifiers, mostly class D with DF > 6000 which could not drive difficult load speakers.

I would suggest to trust "a bit" professional reviewers but more the amplifier's owners review - however, critically i.e. to see what speakers were used, what front end was used etc.

"...The result would be examined for odd-ordered harmonics so a listener fatigue/brightness rating can be assigned. Then the lower ordered harmonics can be analyzed so a low-order coloration (warmth, caramel, syrupy) value can be assigned. "

I believe that John Atkinson from Stereophile does this kind of measurments (his input signal can be subject of discussion) and looking on distortion spectrum - as you discuss above - I have some idea of the sound of the equipment - at least its midrange.

"A lot of research has been done since then, but none of it has been incorporated into the tradition of measurement, and so we have the experience of not being able to tell much of anything about the sound of the amp from its spec."

Simon Thacher from Spectron did study of the rlation between reproduction of musical peaks and listener fatique:
http://www.enjoythemusic.com/magazine/manufacture/0708/index.html

I beleive that Spectron amps are one of the best in that regard - of course, for easy load speakers you don;t need that amount of (distortion-free) power.

So, slowly but we still are moving along to understand relation between some measurments and some aspects of the sound.

Cheers

Hello Athmaspere,

LOVE your posts !!!!

I said that John Atkinson " input signal can be subject of discussion" and this is exactly what you did !

Even more interesting your comment: "... if the waveform is fast enough and lacking manipulation, the limbic system does the processing, but if too slow and certain harmonics are added, the processing is done by the cerebral cortex (emotional vs intellectual). "

Is exactly the same that Simon Thacher of Spectron wrote in the article I referred to:

"...The exploration of the origin of "listener fatigue" is extremely interesting, at least, for this writer. We believe that when our subconscious mind detects a small unnatural trace of distortion in reproduced acoustic music (which is not recognized yet as a very low level irritant by the analytical part of our brain) it activates a subtle alarm. This forces the listener into the tense or alert mode. Indirectly supporting this hypothesis is the common description we hear from Spectron users who utilize the two powerful monoblock amplifiers (7 kW peak power, each): "how relaxing" is my listening now "

Analytical part of the brain is the cortex, of course as you pointed out and emotional (or subconscious mind as Simon calls it) is our old reptilian brain

Its amazing - only from both of you I hear CLEARLY and bearly identically how audio engineering is related to our "undertsanding" of music