Re: Do all amplifiers sound the same?

bear <bearlabs@[EMAIL PROTECTED]
> wrote:
> Steve wrote:
> > Some time ago the now defunct stereo review had an interesting article
> > on blind a/b tests between different amplifiers - I saw a reprint
> > here;
> > 
> > http://bruce.coppola.name/audio/Amp_Sound.pdf
> > 
> > After a hiatus of many years I am now putting together a system and
> > every one I talk to tells me there is a difference between amplifier
> > sounds. I am sceptical and in a recent audition could not tell a Creek
> > EVO from a NAD 325 BEE (through EPOS M12.2 speakers with a Creek cd
> > source).
> > 
> > Has any more work been done on this subject, esp. blind a/b tests?
> > 
> > Steve

> Amplifiers do not all sound the same.
> Some may.
> Some do not.
> They certainly do not measure the same.

> The THD or IM specs do *not* tell the story.

> Those who are still doubters, may review Dr. Earl Geddes research on
> this subject. It provides the necessary scientific and engineering
> basis for the above assertion.

Hopefully it provides the blind test results to demonstrate audible 
difference.

> There are a few other 'confounding" factors to account for when
> an individual is trying to decide these things:
> - there may be masking effects from other parts of the system
> (for example a perfectly blameless amp could not be discriminated
> from one that was not blameless, if there was sufficient "objectionable"
> harmonic signature produced by another element in the system).
> - the listener may or may not have physical deficits that prevent
> such a discrimination.
> - the listener may never have heard a system without many of the
> typical "objectionable" artifacts (no basis for comparison).
> - there may be other factors, including subsonic sound and ultrasonic
> sounds in the environment, excessive reverberation, etc. that
> interfere.

or, the two amps really do not sound different, when used within their 
limits.

> As far as "A/B" or "ABX" tests, they are usually valid for the specific
test
> condition, as made. Suitability of those tests for generalized
> application, if they lack controls for at minimum the above factors, and
> some others (such as basic THD, IM, polar response, room reverberence,
> noise floor, etc...) makes the ones that I have seen published
> so far - that is a preponderance of those I am aware of - not
meaningful.

Double Blind tests have been and continue to be used by Harman for 
generalized application in loudspeaker development.

And amplifier (and cable, btw -- mentioned because you sell 'high end' 
cable that you claim sounds better than plain cable) difference tests have

been done where the listener who claimd to hear difference between *his* 
gear and others, was tested with his gear, against other gear. And failed 
the test.

> Others will disagree, I am sure.

> The key to assembling a system that one enjoys listening to depends on
> one's thresholds for certain types of "irritants" (and avoiding them),
> a bit of luck, serendipity, and in some cases knowledge of matters
> technical and acoustic. Money, per se, does not play the major role
> in this respect, since there is lots of excellent used gear, and the
> possibility of DIY... :_)

Have you ever ABX'd differences in amps, and if so, under what conditions,

and what scores did yuou obtain?

___
-S 
"As human beings, we understand the world through simile, analogy, 
metaphor, narrative and, sometimes, claymation." - B. Mason