Pass Labs X250 specification

The X250 stereo amplifier embodies the design technology and refinements of the larger "X" series amplifiers including extensions of the patented Supersymmetry circuit.

The Supersymmetry circuit topology was granted a U.S. patent in 1994, and is the result of 19 years of effort by Nelson Pass. The amplifier uses highly matched components in a classically simple balanced Class A circuit. The amplifier contains only two simple stages: the first is a balanced Class A voltage gain stage using low noise Jfet input devices followed by complementary Mosfets. Its output drives a bank of high power Mosfets operated as voltage followers.

These are inherently low distortion types of circuits, but their performance is improved when operated in balanced mode through cancellation. Distortion and noise identical to both halves of a balanced circuit will disappear at the output, and in a well-matched symmetric circuit, most of the distortion and noise is identical.

Supersymmetry enhances this effect by providing a connection between the two halves of the balanced circuit that further perfects the match. Any distortion and noise not already identical to the two halves is made identical through feedback by a factor of about 10, and the result is improved cancellation at the output.

Unlike feedback techniques where the goal is to correct for the distortion by feeding a gain stage an inversely distorted signal, Supersymmetry seeks merely to create perfect matching.

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 Supersymmetric circuit delivers another 90% reduction, so that the X series has about 1/100 of the distortion of a conventionally simple amplifier. Actually this ordinary 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, it goes away at the speaker terminals. This gives good measured performance, which because it is produced by a simple circuit, also sounds excellent.

Previously these kinds of simple Class A circuits have been popular for their sound quality in low power amplifiers, but have not found application at high power levels due to excessive distortion and low efficiency. Supersymmetry overcomes this barrier, delivering the sweetness, staging, and detail of very simple circuitry up to kilowatt power levels and beyond.

The X Series amplifiers have the tremendous dynamic range (>150 dB) to do justice to the 24 bit recordings of the 21st Century. The simple but powerful circuitry moves easily from total silence to explosive transient and back to silence without a trace.

So relax and enjoy your amplifier. Call us if you ever have a problem or question. Nelson personally answers his email addressed to nelson@passlabs.com, and you are welcome to ask questions or offer comments. Thank you for buying our product.

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X250 specifications

The Pass Labs X250 is a distinguished power amplifier that showcases the brand's commitment to delivering high-quality audio performance, blending robust engineering with innovative technology. Known for its exceptional build quality and sonic capabilities, the X250 is designed for audiophiles and music enthusiasts who demand the best from their audio equipment.

At its core, the X250 is a Class A/B amplifier, which means it combines the efficiency of Class B with the superior sound quality of Class A. This hybrid design allows the amplifier to deliver high power output while maintaining low distortion levels, resulting in a clean, dynamic sound that captures the essence of the original recording. The amplifier delivers 250 watts into 8 ohms and 500 watts into 4 ohms, making it suitable for driving a wide range of loudspeakers with ease.

One of the standout features of the X250 is its use of Pass Labs' proprietary “Bias Current” technology. This innovative system optimizes performance by ensuring that the output devices operate in their most linear region, reducing crossover distortion and enhancing the amplifier's overall sound quality. This results in a more accurate and natural reproduction of audio, appealing to listeners who seek fidelity above all else.

Another notable characteristic of the X250 is its impressive dynamic range. The amplifier is designed to handle transient peaks with confidence, preserving the impact and nuance of musical passages, whether it's the delicate pluck of a guitar string or the thunderous notes of a full orchestra. The low noise floor further enhances the listening experience, allowing even the quietest details to be heard clearly.

The build quality of the X250 is equally impressive, featuring a rugged chassis and high-grade components that ensure durability and reliability. With its elegant appearance, the amplifier is not only a functional piece of equipment but also an attractive addition to any audio setup. The attention to detail in the design is evident, with a focus on minimizing vibrational interference and maintaining signal integrity.

In conclusion, the Pass Labs X250 is a remarkable power amplifier that combines advanced technology with exceptional sound quality. Its Class A/B design, Bias Current technology, and high power output make it a versatile choice for a wide range of audio applications. For those who value both performance and aesthetics, the Pass Labs X250 stands out as a superb option in the realm of high-fidelity audio amplification.