[Arny Krueger]

"Audio Empire" wrote in message

On Fri, 4 Mar 2011 06:29:00 -0800, Sebastian Kaliszewski
wrote (in article ):

No. The physics and math tell us what the performance
characteristics of the wire is. And of course,
measurements will tell us the quality of the connections.

The same is true for more complex electronics.

Now physics and psychoacustics predict that all A/D, D/A
and amplifier circuits sound the same given their
parameters are within range.

I disagree. Measurements tell us what some of the
performance characteristics of a electronic circuit will
be and the physics and math will characterize that device
to a certain point.

That point is very well refined.

We use maths to design these devices,
they tell us, for instance, what resistors to use to bias
a transistor for the correct current flow, and to set the
feedback for the gain. Maths tell us, what size capacitor
to use to couple the lowest frequency in which we're
interested from stage to stage. Maths also allow us to
tailor filters to our needs and tell us how they will
perform in the frequency domain.

The mathematics all predict nonlinear distortion, etc.

What the physics and
maths don't predict at the design level (among other
things) is the difference in many performance parameters
between components of different qualities.

Not true. The mathematical models for various qualities and types of
components are known and can be plugged into the circuit models.

For instance,
I can design an all transistor amplifier and get all of
the component values right, and yet ruin the design
sonically, just by choosing the wrong kind of component.

Not a problem for the reasons already stated.

A high gain stage might call for 33,000 Ohm resistor. OK,
fine. I'll use a 33,000 Ohm resistor. But if I choose a
carbon composition resistor instead of a metal film, that
high gain stage will be noisy.

You're joking, right? Nobody is using carbon composition resistors these
days.

The maths and physics I
used to design that amplifier didn't predict that, and if
I build TWO such amps, one with metal film resistors and
one with carbon comp resistors, they'll sound different
and anyone will instantly tell them apart in a DBT!

I remember what life was like in the days of carbon composition resistors,
and I also remember what happened on the occasions where I replaced carbon
comp resistors with metal film resistors. In general: Nothing. The problem
was not so much what a good carbon comp resistor did, its what happened when
that resistor went into some of its possible partial failure moded.

Same
thing with capacitor selection. If my design called for a
a series of coupling capacitors capacitor in the signal
path and I used tantalum capacitors in those spots
instead of a some kind of low DA film capacitor like a
polypropylene or a mylar film capacitor, the amp circuit
is going to sound different than it would had I used the
low DA types of capacitors.

Same story. I even had a well-known capacitor dielectric maven whose named
rhymed with bung send me some good and bad capacitors to try in some
projects. The so-called bad capacitors were simply not the part that long
accepted wisdom said should be used in the application. The good capacitors
were film capacitors but in actual use there was no measuable or audible
benefit as compared again to what long accepted wisdom said should be used.

DA is important in sample-and-hold circuits and afew other applications. The
fallacies associated with audio enthusiast misunderstandings of DA have been
explained well by well-known and highly regarded experts such as Robert
Pease of National Semiconductor.

This is not as cut and dry as it seems. While the laws of
physics will predict that the two types of resistors will
have very different self-noise characteristics, that's
not generally a primary consideration when designing an
amplifier.

Absolute and total misrepesentation of generally accepted engineering
standards, even those long before audiophile capacitor parania struck.

Sure, the designer probably knows better than
to use certain components, and what the results would be
if he did, but the physics behind the design exercise
don't encompass those types of choices. They only predict
such things as frequency response, gain, harmonic and
intermodulation distortion and signal-to-noise ratio
based on the parameters of the components used. However,
change the quality of the components and one can make two
identical amplifier sound different, and that's the
point.

There are no known relevant audio circuit design performance parameters
other than linear distortion (phase and frequency response), nonlinear
distortion (harmonic distortion and IM) and noise. People can pretend what
they want, but any other performance parameters only show up in poorly-done
listening tests. IOW, they are false positives.