nested feedback, no feedback, feed forward, Stasis, harmonic time alignment, high slew,
Class AB, Class A, Pure Class A, Class AA, Class A/AB, Class D, Class H, Constant bias,
dynamic bias, optical bias, Real Life Bias, Sustained Plateau Bias, big supplies, smart
supplies, regulated supplies, separate supplies, switching supplies, dynamic headroom,
high current, balanced inputs and balanced outputs.
Apart from digitally recorded source material, things have not changed very much in twenty
five years. Solid state amplifiers still dominate the market, the largest audio magazine still
doesn't hear the difference, and many audiophiles are still hanging on to their tubes.
Leaving aside the examples of marketing hype, we have a large number of attempts to
improve the sound of amplifiers, each attempting to address a hypothesized flaw in the
performance. Audiophiles have voted on the various designs with their pocketbooks, and
products go down in history as classics or are forgotten. The used market speaks
eloquently: Marantz 9's command a high price, while Dyna 120's are largely unwanted.
There has been a failure in the attempt to use specifications to characterize the subtleties of
sonic performance. Amplifiers with similar measurements are not equal, and products with
higher power, wider bandwidth, and lower distortion do not necessarily sound better.
Historically, that amplifier offering the most power, or the lowest IM distortion, or the lowest
THD, or the highest slew rate, or the lowest noise, has not become a classic or even been
more than a modest success.
For a long time there has been faith in the technical community that eventually some
objective analysis would reconcile critical listener's subjective experience with laboratory
measurement. Perhaps this will occur, but in the meantime, audiophiles largely reject bench
specifications as an indicator of audio quality. This is appropriate. Appreciation of audio is
a completely subjective human experience. We should no more let numbers define audio
quality than we would let chemical analysis be the arbiter of fine wines. Measurements can
provide a measure of insight, but are no substitute for human judgment.
As in art, classic audio components are the results of individual efforts and reflect a coherent
underlying philosophy. They make a subjective and an objective statement of quality which
is meant to be appreciated. It is essential that the circuitry of an audio component reflects a
philosophy which address the subjective nature of its performance first and foremost.
Lacking an ability to completely characterize performance in an objective manner, we should
take a step back from the resulting waveform and take into account the process by which it
has been achieved. The history of what has been done to the music is important and must
be considered a part of the result. Everything that has been done to the signal is embedded
in it, however subtly.
Experience correlating what sounds good to knowledge of component design yields some
general guidelines as to what will sound good and what will not:
1) Simplicity and a minimum number of components is a key element, and is well reflected in
the quality of tube designs. The fewer pieces in series with the signal path, the better. This
often true even if adding just one more gain stage will improve the measured specs.
