5
X
s
Owner’s Manual
Our real customers care most about the experience they get when
they sit down to listen to their music. We create amplifiers that we
like to listen to, on the assumption that we share similar taste.
We want our products to invite you to listen. We want you to enjoy
the experience so much that you go through your entire record
collection - again and again. This, by the way, is a very strong
indicator.
A simple survey of really successful audio amplifiers shows
that objective performance numbers by themselves are not that
important. For example, there is some level at which harmonic
distortion is subjectively intrusive – we could probably stipulate that
10% distortion is too much, and would probably accept that 1%
would be audible.
Conversely, we should accept that distortion becomes inaudible
below some arbitrary level. Is it at 0.1%? 0.01%? 0.001%? We
actually don’t know, because there has to be a much larger context of
performance to which a single number only alludes.
In the process of developing the Xs amplifiers, we paid a lot of
attention to the harmonic structure of the amplifier’s transfer curve.
It is apparent that reducing the numerical distortion numbers is not
as important as controlling the relative amounts of the harmonics
and their polarity. Even at low distortion levels, these harmonic
relationships are important to the perception of musical quality, but
they are not reflected in ordinary specifications.
In an amplifier of this sort, the power output stage is where most
of the action is. Playing with developmental tube and SIT designs,
we concluded that it is the character of the power output stage itself
which is most influential in shaping the sound of the amplifier. To
understand what we were looking for, imagine the sound of a low
distortion direct-coupled Triode operated in single-ended Class A.
Then imagine it with lots more power and control.
The original Aleph 0 from 1991 used an output stage which
consisted of a push-pull Class A output stage operated in parallel
with a high constant current output stage. The bias currents were
high enough to operate to rated power in single-ended Class A,
giving it a second harmonic signature, and as a push-pull topology at
higher power levels.
The X.5 and XA.5 amplifiers incorporated the single-ended bias
approach in balanced output stages, but for efficiency reasons did