Pass Labs X2.2 - Manual (Page 6)

6 X2.2 Owner’s Manual
assuring precise level steps and high common-mode rejection in
balanced circuits. Wayne Colburn’s exceptional volume control, in
conjunction with the unique LED display, gives the user the ability
to replicate volume levels with absolute accuracy in steps of roughly
3dB.
1) Circuit simplicity and a minimum number of components is a key
element. The fewer parts in series with the signal path, the better.
Adding more parts and gain stages may improve measured specs,
but will seldom improve the perceived sonic quality or reliability of a
product.
2) The characteristic of gain devices and their specific use is
important. Individual variations in performance between like devices
are important, as are differences in topological usage. All signal
bearing devices contribute to the degradation, but there are some
different characteristics that are worthy of attention. For example,
smooth low order nonlinearities are additive in quality, bringing false
warmth and coloration, while abrupt high order nonlinearities add
harshness and false brightness.
3) Maximum intrinsic linearity is desired. This is the performance
of the gain stages before feedback is applied. Experience suggests
that feedback is a subtractive process; it removes information from
the signal. In many older designs, poor intrinsic linearity has been
corrected by large application of feedback, resulting in loss of
warmth, space, and detail. The trick is to get good performance
without this excessive reliance on feedback.
The art of high end audio design lies in the approach of combining
these elements to get high reliability and simplicity, high quality
measured performance, and high quality subjective performance. It
takes imagination and hard work to get as much of these as possible
at once without trading them off against each other.
We recommend the use of the balanced output mode where possible.
It will retain the character of the input mode, but offers less
distortion, less noise, more gain, and more voltage swing, without
compromising the sound.
With balanced operation, the common-mode rejection of the
preamp reflects the intrinsic common-mode rejection of the
topology, the matching of the gain devices, and the matching of
the attenuator channels. In this case we have been able to keep
Product Philosophy
Other Design Comments