David Nebenzahl wrote:
Again with the "may sound different from other [studio] amps". I've got
to take exception to that as a sort-of audiophool belief.

Go out and listen to some amps. They sound different. The differences
aren't anywhere near as big as the differences between speakers, but they
are clearly audible in an A/B comparison between amps of varying topologies.

By definition, if two amplifiers both have extremely low distortion,
they should "sound" approximately the same, right? Again, this is
*assuming* (see disclaimer below) that other relevant specs (probably
most importantly things like transient response) are in the same
ballpark; I have no reason to believe that they wouldn't be in what
appears to be a high-quality amplifier like this.

Sure, but that just shows that the THD measurement is useless as a measure
of distortion today. Take a look at some of those 1970s amps that relied
on huge amounts of feeback to get linearity. The Dyna ST-120, for instance,
has a really low THD number, but the 1 KHz square wave response into an 8 ohm
load is so bad that it looks visibly screwed up on a scope. It's really good
at reproducing sine waves, but not so good with anything else.

Yes, I understand that I do not know what the other specs for the
amplifier under discussion are; and neither do you. This is Usenet,
remember? not a peer-reviewed engineering paper. So sue me.

I don't know what the actual specifications of the amp are... I have never
done a full distortion spectrum on it, nor have I actually measured the
output impedance or checked out impulse response. Because of that, I have
to rely on my ears.

There are plenty of useful specifications that will tell you a lot about
an amplifier. You will not, however, find them on the manufacturer's data
sheet because the LAST thing the manufacturer wants you to know is how the
product actually performs. Data sheets are marketing information and not
technical information.

THD into a fixed resistive load was useful information back in the 1940s,
when you could assume that all amps had the same basic topology and that
the load would be transformer-matched to the output stage. Today you cannot
make any of these assumptions.
--scott

--
"C'est un Nagra. C'est suisse, et tres, tres precis."