"John Atkinson" wrote in message
om...
(Audio Guy) wrote on r.a.h-e in message
...
Audio is a trivial application, they learn about power supply
design and amplification, which is pretty much all there is to
audio amplifiers, in their early years and then go on to much more
interesting and challenging concepts.
I see statements like this from time to time, yet I am not so sure
that audio design is "trivial." There are not many other design fields
where an amplifier: has to provide up to 30dB of voltage gain; act as a
voltage source into a wide and arbitrary range of load impedances
and do so in an unconditionally stable manner; have a passband noise
contribution at least 90dB down from 1W into 8 ohms, no matter what
its voltage gain and ultimate power delivery; have distortion
components under all load conditions that are below the threshold of
hearing no matter what the program material is; and do all the above
over at least three-decade, ie, a 10-octave passband.
Thoughts, gentlemen? I would suggest that designing, say, a typical RF
amplifier is, by comparison, "trivial" but, of course, I may just be
missing something :-)
John Atkinson
Editor, Stereophile
I don't think it's trivial at all.
It does, however, tend to be canonical, which means the devil is in the
details, rather than a new overarching concept which probably does not
exist.
It might be interesting to enumerate the design concepts for solid state
amplifiers which have occurred. I would guess the number to be less than
twenty, in two groups:
1. Device physics
2. Circuit topology
From the examples I've seen, written about primarily in Stereophile --
though the Acoustat was covered in "Audio", it would seem that the result is
limited more by the design budget than anything else. The more components,
as in active constant current sources, higher quality parts, stiffer
supplies, etc., one can throw at it, the better the result. The end game
example of this is that Australian amp (name, please?) that has far lower
levels of distortion than anything else.
That amplifier is an important example, because it tends to negate the worth
of the "boutique designs" that emphasize some particular parameter at the
expense of others. That is another area that I've never found real happiness
with, in comparison to amplifiers engineered for general goodness.
Oddly, although amplifier design has become mature, it does not appear to me
that specification and testing has. The scientist in me says it all has to
reduce to numbers, yet it does not, which means that the numbers are
obtained by test procedures that fail to characterize amplifier behavior.
Someone ought to work on this.