Page 2
The X250 stereo amplifier embodies the design technology and refinements of the larger "X"
series amplifiers including extensions of the patented Supersymmetry circuit.
The Supersymmetry circuit topology was granted a U.S. patent in 1994, and is the result of 19
years of effort by Nelson Pass. The amplifier uses highly matched components in a classically
simple balanced Class A circuit. The amplifier contains only two simple stages: the first is a
balanced Class A voltage gain stage using low noise Jfet input devices followed by
complementary Mosfets. Its output drives a bank of high power Mosfets operated as voltage
followers.
These are inherently low distortion types of circuits, but their performance is improved when
operated in balanced mode through cancellation. Distortion and noise identical to both halves
of a balanced circuit will disappear at the output, and in a well-matched symmetric circuit, most
of the distortion and noise is identical.
Supersymmetry enhances this effect by providing a connection between the two halves of the
balanced circuit that further perfects the match. Any distortion and noise not already identical
to the two halves is made identical through feedback by a factor of about 10, and the result is
improved cancellation at the output.
Unlike feedback techniques where the goal is to correct for the distortion by feeding a gain
stage an inversely distorted signal, Supersymmetry seeks merely to create perfect matching.
Matched balanced power circuitry typically sees a distortion and noise reduction of about 90%
(20 dB) through a balanced connection without any additional effort. The Supersymmetric
circuit delivers another 90% reduction, so that the X series has about 1/100 of the distortion of
a conventionally simple amplifier. Actually this ordinary distortion and noise can still be seen at
the output of one half of the circuit, but since it is virtually identical on the other half, it goes
away at the speaker terminals. This gives good measured performance, which because it is
produced by a simple circuit, also sounds excellent.
Previously these kinds of simple Class A circuits have been popular for their sound quality in
low power amplifiers, but have not found application at high power levels due to excessive
distortion and low efficiency. Supersymmetry overcomes this barrier, delivering the
sweetness, staging, and detail of very simple circuitry up to kilowatt power levels and beyond.
The X Series amplifiers have the tremendous dynamic range (>150 dB) to do justice to the 24
bit recordings of the 21
st
Century. The simple but powerful circuitry moves easily from total
silence to explosive transient and back to silence without a trace.
So relax and enjoy your amplifier. Call us if you ever have a problem or question. Nelson
personally answers his email addressed to
, and you are welcome to
ask questions or offer comments. Thank you for buying our product.
