XA White Paper:

Like Peanut Butter and

Chocolate

© Nelson Pass

X Supersymmetry™

XA60 Owner’s Manual

Sometimes two designs complement each other so well that you are surprised when you learn they weren’t invented together. So it is with the X Supersymmetery™ amplifier and the Aleph single-ended Class A output circuit.

The Supersymmetery™ “X” amplifier repeatedly demonstrates the pos- sibilities for very high power, dramatic dynamic contrast, and effortless control by a simple circuit utilizing absolutely minimal feedback. As with the art of Aikido, the X circuit works with the intrinsic character of a balanced circuit and deftly turns that character toward perfection. This has been the basis for a very successful Pass Laboratories™ prod- uct series, which has won numerous prestigious awards and garnered critical acclaim worldwide.

For over ten years, the Aleph™ series of single-ended Class A ampli- fiers have received praise for their outstanding sonic definition, warmth, and smoothness; and have often been compared favorably with the very best tube amplifiers. The Aleph™ topology achieves state-of-the-art performance with a very simple linear design, and is additionally one of the most stable and reliable audio amplifiers in existence.

A considerable number of audiophiles have found themselves bi-amp- ing their loudspeakers, putting Pass Laboratories™ X amplifiers on the bottom for power and control, conjoined with Alephs™ on the top for that smooth warm midrange and top end. We well appreciate these complementary differences, and for the past few years Pass Laborato- ries™ has been at work marrying these two design concepts into a single amplifier topology. The trick was to create an amplifier, which carries the best of both designs, and not otherwise.

The Supersymmetry™ X amplifier uses a new radical approach to achieving high performance from a simple 2-stage circuit. The design exploits the symmetry of a matched balanced amplifier so that distor- tion and noise are cancelled at the output to the loudspeaker, then uses a small dose of a unique new form of feedback to make that symmetry more perfect.

US Patent # 5,376,899 describes our topology, which takes advantage of the character of specially matched balanced amplifiers that are cross- coupled to provide cancellation of distortion and noise. The result provides high performance with very simple linear circuits, better than previous similar efforts by an order of magnitude. It was named Super- symmetry™ as an homage to particle physics, but it is popularly known as the X circuit.

Balanced amplifiers improve performance by differentially rejecting dis- tortion and noise. To the extent that distortion and noise are identical,

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Pass Labs XA60 owner manual XA White Paper Like Peanut Butter Chocolate, Supersymmetry
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XA60 specifications

Pass Labs XA60 is a high-performance audio power amplifier that epitomizes the pursuit of sonic purity and fidelity in the realm of high-end audio. It is the entry-level model in the esteemed XA series, but still incorporates many of the advanced technologies and features found in its more powerful siblings. Designed with a focus on delivering an immersive listening experience, the XA60 combines state-of-the-art engineering with superior craftsmanship.

One of the key features of the XA60 is its Class A topology, which ensures that the amplifier operates in the linear region for the entirety of its output range. This design lends itself to a warm, natural sound that captures the nuances of music without the harshness often associated with other amplifier classes. The XA60 is capable of delivering 60 watts per channel into an 8-ohm load, making it ideal for driving a variety of loudspeakers, including high-efficiency models.

The amplifier employs Pass Labs' patented "Pure Class A" output stage, which utilizes a unique biasing method to minimize crossover distortion. This innovative approach enhances the overall sonic clarity and dynamic range, allowing the XA60 to reproduce even the most complex musical passages with ease. Additionally, the amplifier is characterized by its dual-mono design, isolating the left and right channels to reduce crosstalk and interference, which ultimately results in a more focused soundstage.

Another standout characteristic of the XA60 is its massive power supply. The highly refined power supply includes large heatsinks and high-quality components that help maintain stability and reduce noise during operation. The robust thermal management ensures that the amplifier remains cool, even during extended listening sessions, thus preserving the integrity of the sound.

The build quality of the XA60 is nothing short of exceptional. Housed in a sturdy chassis, the amplifier features premium-grade connectors and a simple, yet elegant aesthetic that is typical of Pass Labs products. The thoughtful design not only ensures durability but also aids in minimizing vibration, further enhancing acoustic performance.

In summary, the Pass Labs XA60 amplifier represents a harmonious blend of advanced technologies, exceptional sound quality, and impeccable craftsmanship. With its Class A operation, dual-mono architecture, and high-quality components, the XA60 provides a nuanced, engaging listening experience that appeals to audiophiles seeking both precision and warmth in their audio systems. Whether used in a dedicated listening room or as part of a larger home audio setup, the XA60 is engineered to deliver music as it was meant to be heard.
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