Aleph Single-Ended Class A

The Supersymmetery Aleph™

XA60 Owner’s Manual

they vanish at the output, typically by a factor of 10 or so for matched single-ended Class A circuits.

Supersymmetry™ extends this concept by using feedback only to make the distortion and noise more identical on each half of a balanced cir- cuit, not to eliminate it as such. This gives as much as a 100:1 reduc- tion in unwanted distortion and noise without requiring the equivalent amount of negative feedback. It is simply much easier to tweak the two halves of the circuit into identical symmetry than to eliminate all the distortion in each half of the circuit.

The result has been a successful series of high power amplifiers offering low distortion, and stunning dynamic range and control, with only two gain stages and very minimal feedback.

Supersymmetry™ is ideally used to obtain high quality performance from very simple gain circuits, and particularly favors single-ended Class A topologies due to their smooth second harmonic characteristic, which cancels easily.

Single-ended Class A has long been known as the “King of the Class A’s”, the simplest, most pure and least efficient form of audio amplifi- cation. Before the Aleph™ amplifiers, it was reserved for preamplifier circuits, high quality amplifier front-ends, and other very low power output stages.

US Patent # 5,710,522 describes the single-ended Class A power ampli- fier biased by a constant DC current source which negatively “ghosts” the speaker load with simple but effective current modulation. If you have followed developments in audio for the last 10 years, you know this design as the Pass Laboratories Aleph™. The Aleph™ is an incredibly successful ground breaking amplifier design, hailed in Stereophile maga- zine as “The Amplifier of the Decade” and winner of virtually every international design award for audio that we know of.

The key virtue of the Aleph™ design lies in its simplicity and effective- ness. With only two stages and no adjustments it delivers measured performance rivaling the most complex designs, but retains the sonic elegance and nuance of a truly minimalist gain path – only two gain devices in series from input to output.

The two design concepts are not mutually exclusive, and we approached the development of the XA series with an eye to creating a warm/sweet X amplifier, or conversely, a powerfully dynamic Aleph™. The success- ful result is a circuit which is described as balanced single-ended Class A, consisting of two balanced Aleph™ amplifiers sharing a single dif- ferential input pair of transistors.

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Pass Labs XA60 owner manual Aleph Single-Ended Class a
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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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