X150.8 Stereo Amplifier

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150W per channel and 100 Kohm input impedance, a powerhouse amp More details

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The Pass Labs X150.8 Stereo amplifier is a formidable powerhouse designed to elevate your audio experience to new heights. The X150.8 is a stereo amplifier that delivers 150 watts per channel into 8 ohms, showcasing Pass Labs' renowned Class A/B topology for exceptional sound quality. With its symmetrical circuitry and meticulously selected components, this amplifier ensures pristine audio reproduction with breathtaking dynamics. The X150.8 features a robust power supply and large heat sinks for reliable and stable performance, even when driving demanding speakers. Equipped with balanced (XLR) and single-ended (RCA) inputs, along with a minimalist and elegant design, the Pass Labs X150.8 is a statement piece for audiophiles seeking uncompromising sound quality and craftsmanship in their audio systems.

Dragon Cable Recommendation: we recommend pairing the X150.8 stereo amplifier with our award-winning Bronze Dragon Interconnects. The Bronze Dragon Interconnect is one of our best-selling cables at Moon Audio. With a braided geometry and amazing shielding, this interconnect is a remarkable solution where noise isolation is key. The Black Dragon Power Cable is also recommended to provide the cleanest and unbridled power to your high-end amplifier.

The Pass Labs X150.8 Stereo amplifier boasts an impressive array of features designed to deliver exceptional audio performance:

  1. Class A/B Topology: Utilizes Pass Labs' renowned Class A/B topology for outstanding sound quality and low distortion.
  2. 150 Watts per Channel: Provides 150 watts of power per channel into 8 ohms, suitable for a wide range of speakers.
  3. Symmetrical Circuitry: Ensures balanced and accurate audio reproduction, capturing fine musical details.
  4. High-Quality Components: Meticulously selected components contribute to the amplifier's exceptional sound clarity and dynamics.
  5. Robust Power Supply: Features a robust power supply for stable and reliable performance, even with demanding speakers.
  6. Large Heat Sinks: Equipped with large heat sinks to dissipate heat efficiently, ensuring optimal performance over extended listening sessions.
  7. Balanced (XLR) and Single-Ended (RCA) Inputs: Offers both balanced and single-ended inputs for flexible connectivity options.
  8. Precision Volume Control: Features precise volume control for fine adjustments to suit individual listening preferences.
  9. Minimalist Design: Boasts a clean and minimalist design that reflects Pass Labs' commitment to simplicity and performance.
  10. Efficient Loudspeaker Compatibility: Ideal for use with a wide variety of loudspeakers, providing engaging and detailed sound reproduction.
  11. Reliable Performance: The X150.8 amplifier is designed for reliability and long-term performance, requiring minimal adjustments.
  12. Musicality: Known for its musicality, the X150.8 amplifier allows listeners to fully immerse themselves in the nuances of their favorite music.
  13. Exceptional Transparency: Delivers exceptional transparency and clarity, allowing the listener to hear every detail in the music.
  14. Solid-State Design: Offers the benefits of solid-state amplification, including efficiency, reliability, and stable performance.

The Pass Labs X150.8 stereo amplifier offers an impressive 150 watts per channel, providing ample power to drive a wide range of speakers with authority and finesse. With an input impedance of 100K ohms, it ensures compatibility with various audio sources and systems. What sets the X150.8 apart is its operation at a higher level into Class A compared to its predecessors, resulting in exceptionally clean and distortion-free sound reproduction. This advancement not only enhances its measured performance but also translates into an outstanding subjective musical experience. The X150.8 bridges the gap between technical excellence and emotional engagement, inviting listeners to immerse themselves in their favorite music with newfound depth and clarity.

Positioned as the entry-level class A/B stereo power .8 amplifier, the Pass Labs X150.8 inherits numerous technical and sonic attributes from its larger siblings. Boasting 150 watts per channel and a 100K ohm input impedance, it stands ready to deliver powerful and nuanced sound to a variety of speaker setups. What truly sets the X150.8 apart is its operation "higher" into Class A compared to its predecessors, ensuring a cleaner, more detailed sound signature. However, recognizing that the ear is not a microphone and the brain is not a tape recorder, we've meticulously designed this model to bridge the gap between measured performance and the sheer pleasure of music listening. The X150.8 promises to reignite your passion for music, compelling you to rediscover every nuance and emotion in your cherished collection, one track at a time.

Pass Labs and First Watt

Pass Labs and First Watt were founded by hi-fi legend Nelson Pass. After co-founding and later selling Threshold Audio, Pass began working out of his Auburn, California, home in the early 1990s to develop prototypes of single-ended Class A amplifier designs under the name Pass Labs. Pass Labs quickly became known for its commercially produced Aleph, X, and XA Series amps, and preamps. Pass later started First Watt as a passion project focusing on low-power amps for a niche audiophile audience. Today, Pass splits his time between the two companies, with production happening in Pass Labs' facility in Foresthill, California.


What is the power output of the Pass Labs X150.8 Stereo Amplifier?

The Pass Labs X150.8 Stereo Amplifier delivers 150 Watts per channel into 8 ohms. This robust power output, combined with its Class A/AB operation, provides ample power for a wide range of speakers. The X150.8 is designed to deliver clean and dynamic sound, making it suitable for both moderate and more demanding speaker loads.

What are the key features of the Pass Labs X150.8 Stereo Amplifier?

The Pass Labs X150.8 is designed with audiophile-grade components and meticulous attention to detail. It features a fully balanced input stage and a high-current, Class A/AB output stage for low distortion and musicality. The X150.8 includes Pass Labs' proprietary Super-Symmetry circuitry for improved performance and a precision volume control for accurate level adjustments. It also offers a remote control for convenience and a home theater bypass mode for integration into multi-channel systems.

Can the Pass Labs X150.8 drive a variety of speakers, including those with lower impedances?

Yes, the Pass Labs X150.8 Stereo Amplifier is designed to drive a wide range of speakers effectively. With its 150 Watts per channel into 8 ohms (300 Watts into 4 ohms), the X150.8 has the power and control to handle various speaker loads. Whether driving moderately efficient speakers or those with lower impedances, the X150.8 delivers a clean and detailed sound with excellent dynamics.

Does the Pass Labs X150.8 require any special considerations for setup or maintenance?

The Pass Labs X150.8 Stereo Amplifier is designed for straightforward setup and operation. It does not require bias adjustments, as it is a self-biasing Class A/AB design. However, users should ensure proper ventilation for optimal performance, as high-powered amplifiers can generate heat. Adequate ventilation will help maintain the amplifier's performance and longevity. Additionally, it is recommended to provide sufficient space around the amplifier for airflow and to follow Pass Labs' guidelines for safe and optimal operation.

Who is Nelson Pass?

Nelson Pass, the man behind Pass Labs and First Watt, has been designing and building amplifiers for decades. His early passion, however, was speakers; at age 14, he started assembling loudspeakers. As a college student studying physics at the University of California-Davis, he co-founded a speaker company called PMA. He also worked for ESS, where he designed crossovers and enclosures. After college, with his interest having shifted toward amplifiers, Pass co-founded Threshold Electronics (now Threshold Audio). His achievements during the Threshold years include developing the first dynamically biased Class A amplifier circuit; developing a fully cascode audio power amplifier; and developing the STASIS stereo preamplifier and power amplifier. During the 1980s, Pass designed the Adcom GFA-555 amplifier. Later, after selling Threshold, he started Pass Labs in 1991 and First Watt in 1997. Pass holds several patents related to audio circuits.

How did Pass Labs make its name?

Pass Labs helped popularize solid-state, Class A power amplifiers. Pass Labs' first product, the Aleph 0 amplifier, operated as single-ended Class A up to its 70 watt rating and in push pull Class A at higher wattage. The Aleph series of amplifiers, some of the first solid-state amps that were said to be "tube-like" in sound, operated pure class A and contained internal circuitry using MOSFETs. The Aleph amplifiers had a unique appearance, a cube with heat sinks on all four sides, a solution to the heat generated by the class-A design. This can be attributed primarily to the specific MOSFETs used and the minimum number of gain stages that were implemented in the design. Pass Labs also developed the Super-Symmetry™ ("Su-Sy") circuit, which achieves exceptionally low distortion and noise levels. In 1998, Pass Labs released the X1000, the first amplifier using the patented SuperSymmetric™ topology. The X1000 achieved 1000 watts with high performance, local feedback and only two gain stages: a cascoded differential pair of transistors and a large bank of complementary output followers. This groundbreaking design informed all subsequent Pass Labs amplifiers.

What else does Pass Labs make?

In 2002, Pass Labs unveiled the first XA amplifiers, combining the X and Aleph topologies into balanced single-ended Class A amplifiers with many of the characteristics of both the X and Aleph series. The current Pass Labs lineup includes Class A amps (XA and Xs Series), Class AB amps (.8 Series), line preamps (Xs and XP Series), phono preamps (Xs and XP Series), integrated amps (INT Series), and one headphone amp.

What is the relationship between Pass Labs and First Watt?

When he started Pass Labs, Pass did everything out of his home. In 1997, having outgrown the space, Pass Labs moved into commercial space in Foresthill, California. When Pass started First Watt, it was a "kitchen table" venture, with work once again happening in his home. In 2016, with production demands not leaving him enough time to pursue the vast array of yet-to-be-designed amps, Nelson handed the business end of First Watt over to Pass Labs. Pass Labs took over the building of First Watt amplifiers as well as marketing and distribution. There's a synergy between the two operations, in that Pass Labs gets to gather up some of the more interesting First Watt finds and repurpose them as more commercially viable designs. Today, Pass splits his time between First Watt and Pass Laboratories.


Gain (dB)
Full Pwr @ 26 dB gain (V)
Low Frequency Response
1.5 Hz
High Frequency Response
100 KHz
Power Output /ch (8 ohm)
Distortion (1 KHz, full power)
Input Impedance (SE & BAL Kohms)
Damping Factor
Output Noise (uV)
Current Draw @ Idle (Amps)
Power Consumption (Watts)
Temperature (deg C.)
Number of Chassis
Unit Dimensions (W x D x H)
19 x 21.25 x 7.5
Unit Weight (LBS)