"Sander deWaal" wrote in message


How can I make useful sound files available to anyone of
my class A hybrid amps, in order to make a meaningful
comparison with another amp via PC-ABX?

Both amps should be driven by the same recording, the same
source, at relevant levels. A good source would be a number
of high quality digital recordings strung together, with
some test tones for level setting at the front.

Get a really good computer audio interface, load the amp
with a relevant load, attenuate a portion of the amps output
to match the input of the interface, and record the
attenuated output of the amp with the audio interface.

A pair of high quality 5K 2-watt carbon composition
potentiometers make a good power amp output attenuator.

I am currently recommending the M-Audio Audiophile 24192 as
a reasonably-priced but *overkill-enough* audio interface.
It works on PCs and I think Macs as well.

One you have made your digital recordings of the outputs of
the amps, use the test tones to match levels. Ensure that
the recordings have identical start and stop points within a
few milliseconds.

I use Adobe Audition for this, but the freebie Audacity
software looks like it has all the necessary tools as well.
I think Audacity runs on both PCs and Macs as well.

Most PCABX Compartors accept .wav files of any sample type
and rate that the local audio interface will handle.

It can also be useful to compare the input file to any
output files for the equivalent of a "Straight Wire Bypass
Test".

You can re-record the output recordings again and again to
simulate the effects of passing the test music through a
string of amplifiers. These files also are good for training
purposes. Even the best power amps can usually be heard
goofing-up the sound after 10 passes, for example.

Recently, Mike McKelvy and I were discussing the various
topologies of our respective amps, and we thought it
would be interesting to compare my amps with his Acoustat.
If this could be done via PCABX, it would save us a great
deal of shipping costs for a comparison IRL.

Thet's the big advantage of PCABX - you don't need to ship
equipment, just sound files. You can even do stereo
comparisons of amps for which only one channel is available.