shauns@vice.UUCP (Shaun Simpkins) (07/03/84)
Something really bugs me about statements like, to paraphrase Phil R.,
"FET amps shouldn't sound different than Bipolar amps. What does reality
tell us?".
How would one go about this normally? Well, I'd just get a FET amp from one
manufacturer, a Bipolar amp from another, equalize levels, listen, and judge,
right? Uh, no. What we're trying to do here is discern the differences
between active elements. By taking two different amps from two different
manufacturers, I guarantee you that we've also taken two different amplifier
topologies, beyond that needed to take into account biasing differences.
I bet you what we hear first is gross differences in system configuration, not
active elements.
What I would consider a more valid test of active elements is:
1) decide on a common amplifier configuration, say basic Op-Amp -
high-gain stage followed by level shift followed by low impedance output
driver;
2) determine biasing requirements for each active element;
3) mix, match, and listen appropriately.
By blindly listening to different amps from different manufacturers, all we
can really say is, if a particular amplifier sounds better to us, it is
because that amp's designer did a better job of minimizing the transfer
elements' imperfections. We can't say that active element X is better than
active element Y - we haven't isolated all the variables.
Comments?
The wandering squash,
--
Shaun Simpkins
uucp: {ucbvax,decvax,chico,pur-ee,cbosg,ihnss}!teklabs!tekcad!vice!shauns
CSnet: shauns@tek
ARPAnet:shauns.tek@rand-relaypmr@drutx.UUCP (Rastocny) (07/05/84)
I couldn't agree with Shaun S. more. There are greater differences in
amplifiers than meet the eye (ear? :-). Amplifier A sounds different
from amplifier B, no matter what similar/dissimilar active devices are
used (see article title) and no matter if it's a pre-preamp, a preamp,
or a basic amp. Well designed circuits must consider more than the
schematic shows and more than the THD/IM/TIM analyzer measures. It was
the intent of the original article to get people thinking about why amps
sound different and what relates to these differences. Some people call
this "mystical thinking." I call it reality.
---> Literally anything you hear can be measured <---
but finding the right measurement may be a bit tricky. Now if we could
only convince people like STEREO REVIEW...
Yours for higher fidelity,
Phil Rastocny
AT&T-ISL
..!drutx!pmr