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.

X350.5 specifications

The Pass Labs X350.5 is a high-performance power amplifier renowned for its exceptional sound quality and cutting-edge technology. Designed by acclaimed audio engineer Nelson Pass, the X350.5 embodies a commitment to delivering a rich and immersive listening experience, making it a favorite among audiophiles and music enthusiasts alike.

One of the standout features of the X350.5 is its Class A/B amplifier design. This brilliant configuration allows for a balance between high efficiency and class A sound reproduction. The amplifier operates in pure Class A mode for lower power demands, providing a pristine audio signal with reduced distortion. When power requirements increase, it seamlessly transitions to Class AB operation, ensuring consistent performance across a wide range of playback levels.

The X350.5 is rated for 350 watts per channel into 8 ohms, which provides ample power to drive even the most demanding loudspeakers. Its ability to deliver 700 watts into 4 ohms ensures that dynamic peaks in music are handled effortlessly, preserving the integrity of the audio signal. This capability is further enhanced by the amplifier’s robust power supply, which features a substantial toroidal transformer and large reservoir capacitors, ensuring adequate power is always available for high transient demands.

Another defining characteristic of the X350.5 is its innovative thermal management system. The amplifier utilizes a patented biased circuit that keeps the output devices within an optimal temperature range, enhancing longevity and reliability while maintaining sound performance. The unique design also incorporates oversized heat sinks that dissipate heat efficiently, allowing the amplifier to operate cool under heavy loads.

The X350.5 features a balanced and unbalanced input configuration, making it versatile enough to integrate seamlessly into various audio setups. The careful attention to detail in the internal component quality and layout reflects Pass Labs’ dedication to minimizing noise and maximizing signal integrity.

With its sophisticated design, the Pass Labs X350.5 offers audiophiles an unrivaled listening experience, characterized by rich timbre, precise imaging, and expansive soundstage. This amplifier is not merely a piece of equipment; it's an invitation to experience music as it was meant to be heard, bringing recordings to life in the comfort of one's home. The X350.5 exemplifies Pass Labs' philosophy of combining art and precision in the pursuit of audio excellence.