Pass Labs 5XA30.5, Amplifier specification

Nelson Pass has been designing audio electronics since about 1971, first with ESS (remember Heil transformers?), and then forming a new company, Threshold in 1975. Threshold pioneered the design of high power Class A power amplifiers and later, high power amplifiers using only local feedback (the Stasis series).

Pass sold Threshold and created Pass Laboratories in 1991, where he concentrated first on elevating single-ended Class A power amplifiers to new power levels and performance, the Aleph series.

Along the way he found the time to design successful lines of amplifiers for such companies as Adcom and Nakamichi, and has contributed approximately 60 designs (so far) to the public “Do-It- Yourself ” hobbyist community.

Over the years, Nelson Pass has made power, simplicity, and performance his design signature. The hardware tends to run heavy and hot, but elicits high performance and reliability from simple circuits with little or no negative feedback..

In 1998 Pass Labs released the X series of audio power amplifiers, based on the “SuperSymmetric” topology (U.S. Patent #5,376,899) which elicits high power and performance from simple circuits with minimal feedback.

The first X amplifier, the X1000 was intended as the premier example of the power of this principle, delivering 1000 watts rms into 8 ohms at low distortion. By itself of course, this is no miracle, but you have to consider that products with comparable performance have complicated circuits with as many as nine consecutive gain stages and lots and lots of negative feedback. The X1000 had only two stages and used only local feedback.

The difference was the unique balanced circuit topology in which circuit errors are replicated at both output terminals so as to cancel and disappear across the loudspeaker terminals. The high quality of the sound reflects both the low distortion and simplicity of the gain path.

The SuperSymmetric circuit consists of two identical matched circuits arranged like the wings of a butterfly, showing symmetry from left to right, and operating balanced to the loudspeaker. The amplified signal appears with opposing phase across the loudspeaker. Most of the distortion and noise appears in phase across the loudspeaker, and is not seen.

XA30.5 Owner’s Manual

Amplifier, 5XA30.5 specifications

Pass Labs has long been synonymous with high-performance audio amplification, and their 5XA30.5 amplifier is a testament to their commitment to quality and engineering excellence. The 5XA30.5 is an exceptional Class A amplifier designed for audiophiles seeking purity in sound reproduction. One of its standout features is its power output; delivering 30 watts per channel into 8 ohms and a doubled output into 4 ohms, it provides ample power for driving a range of loudspeakers with ease.

One of the key technologies employed in the 5XA30.5 is its Class A circuitry. Unlike other amplification classes that switch on and off to produce sound, Class A amplifiers operate continuously, ensuring that the signal remains uncorrupted. This results in a rich, warm sound that faithfully represents the original recording. The design eliminates crossover distortion, a common issue in other classes of amplification, thus enabling the 5XA30.5 to deliver detailed and smooth audio performance, even at lower volumes.

The amplifier's robust construction further enhances its performance. With a fully balanced differential input stage, the 5XA30.5 minimizes noise and distortion, ensuring that the sound remains crisp and clear. The use of custom-designed output transistors offers superior linearity and thermal stability. Additionally, the generous power supply, equipped with a hefty transformer and ample capacitance, allows the amplifier to handle dynamic peaks without strain, preserving the integrity of the audio signal.

Another notable characteristic of the 5XA30.5 is its elegant design. The aesthetics include a minimalist chassis, machined aluminum front panel, and dual meters that provide real-time performance feedback, allowing audiophiles to observe the amplifier’s operation. Furthermore, it features both single-ended and balanced inputs, offering compatibility with a variety of source components.

Importantly, the 5XA30.5 embodies Pass Labs' philosophy of "the art of amplifier design," resulting in a product that not only performs exceptionally well but also maintains a timeless appeal. Whether for critical listening or enjoying music in a relaxed setting, the Pass Labs 5XA30.5 amplifier promises an unparalleled auditory experience, fulfilling the demands of even the most discerning audiophile. In a landscape where many amplifiers prioritize features over fidelity, the 5XA30.5 remains a beacon of true sound reproductions, demonstrating that exceptional quality and craftsmanship can coexist harmoniously.