Pass Labs X350.5 owner manual Introduction

Introduction

X350.5 Owners Manual

The Pass Laboratories ™ X350.5 stereo amplifier embodies the de- sign technology and refinements of the “X” series amplifiers includ- ing extensions of the patented Supersymmetry™ circuit. Additionally selected refinements of the XA series amplifiers have been incorpo- rated into the X350.5 to significantly improve this products sonic performance in comparison to it’s immediate predecessor, the Pass Laboratories™ X350.

The Supersymmetry™ circuit topology was granted a U.S. patent in 1994, and was the result of 19 years of effort by legendary analog designer and company founder Nelson Pass. The amplifier uses highly matched components in a classically simple single ended Class A circuit. The amplifier contains only two simple stages: the first is a balanced Class A gain stage. Its output drives a bank of high power devices operated as followers.

These are inherently low distortion types of circuits, but their perfor- mance is significantly improved when operated as balanced devices. Distortion and noise identical to both halves of a balanced circuit can be made to disappear at the output, and in a well-matched symmetric circuit, most of the distortion and noise is identical.

Pass Laboratories Supersymmetry™ enhances this effect by provid- ing a connection between the two halves of the balanced circuit that further perfects the match of common mode artifacts. Any distor- tion and noise not already identical to the two halves is made more identical by a factor of about 10. The result of this perfected match is improved noise cancellation at the output of the amplifier. From a listeners standpoint this results in a more accurate presentation of the soundstage and better resolution of low level detail.

Unlike feedback techniques where the goal is to correct for the distor- tion by feeding a gain stage an inversely distorted signal, Supersymme- try™ seeks merely to create perfect matching between the two halves of an otherwise well matched circuit.

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 Supersymmetry™ circuit delivers another 90% reduction, so that the X series has about 1/100 of the distortion of a conventionally simple and otherwise identical ampli- fier. 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, these un- desirable artifacts largely go away at the speaker terminals. This gives good measured performance, and because a simple circuit produces it, also sounds quiet excellent.

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