Pass Labs Xa25 Power Amp

Many audio enthusiasts can’t resist the sound of large, powerful amplifiers. The market of these products is quite alluring, and those who fantasize about all the muscles in the modern amps often find themselves paying top dollar for them. 

Instead, I would invest in smaller ultra-high-quality amps rather than buy something with all the latest bells and whistles. A year ago, I reviewed the F7 amp, but now I’m reviewing the xa25. Xa25 has it’s  incredible-sounding 20-watt per channel performs as well as most other amps in the market.

And now there is something even better – the Pass Labs XA25 amplifier. This is a small integrated best stereo amplifier that combines beauty, simplicity, and the function into one. And I will be reviewing the Pass Labs XA25 stereo so you can decide whether it’s the right fit for you.

About Pass Labs

Before I review this xa25 product, I would like to take you through the brand. This is just to make you understand that this is one of my favorite products. Let’s first discuss Nelson Pass, the head of Pass World, First Watt, and PASSdiy.

Passlabs has been one of the most admired figures in audio design since 1970. But his passion for audio related things dates back to his youths. He started building a DIY project, starting with loudspeakers at the age of 15. Later he joined the world of amplifiers. He was born in Massachusetts, and later moved to Los Angeles in 1957 with his family and then to Santa Maria in 1958. He grew up here and completed his studies in Physics in 1974 from the University of California.

Nelson gained a lot of his knowledge about designing loudspeakers and the amplifiers during his life as a physics student. He was later hired by ESS to do a study and development of loudspeaker crossovers and enclosure design. He worked with the company between 1972 and 1973, which helped him gain an abundance of audio circuit design knowledge. He studied the schematics of op-amps in the National Semiconductor application books.

After this, he did a lot of repairs for all brands of amplifiers for Sun Stereo, where he was the service manager. This was a catalytic moment for him to develop his interest in amps. Most solid-state amps were using Class AB or B designs, yet they never sounded as good as Class A vacuum tube amps. Hence, he wanted to improve on the sound quality of the solid-state amplifiers.

His first unique amplifier design came in 1973 as a Class A solid-state design. He continued to put together the knowledge he gained through his study and work experience until he and a few friends from the ESS founded Threshold Audio.

Nelson mostly worked on the amplifier circuit design while his friend Rene dealt with industrial designs. They created the Threshold 800A as their first-Class A amp that offered 200 Watts per channel, transferring into 8 ohms. This became a hit product for many audio lovers around the world. This xa25 is completely different and unlike their pass labs xa30 amplifier.

Pass labs

In 1991, Nelson exited Threshold Audio to start Pass Labs because he was looking for a larger room to put his investigation into practice. With the company, he used his own audio design interests to help more passionate audiophiles in the world. Today, Pass Labs is one of the leading manufacturers of a full range of audio electronics. These include amplifiers, preamplifiers, integrated amps, and headphone amps. For nearly three decades, Pass labs has been innovating and have their rights reserved, so finally the xa25 has been released.

About Pass labs XA25

Their industry experience only showcases their superior expertise. Pass Labs offer some of the most incredible solutions for modern audio needs. They have features that can benefit just about everyone. The high-end X600.8 monaural amplifiers deliver 600 ways of performance into 8 ohms speakers. It also has a lower power scale that pumps 25 watts per channel into 8 ohms. Pass laboratories xa25 has continuously been innovating new products and this is just their latest invention. The latest xa25 has the build more robust than other amps and better power.


The pass labs XA25 amplifier is a relatively small compared to the XA.8 series. This means it is more portable and may not be for those seeking the top features on the market. However, it is quite the power amplifier. However, even the smaller amps can produce incredible sound, proven by the xa25. It measures only 6-inches high, 17-inch long and 17.315 inches wide with a weight of 55 pounds.

I noticed straight from the box that it does not come with the bias meter found in front of the other XA.8 Series amps. Instead, the xa25 comes with a silver front plate that simply bears a push-button on and off switch, and one blue LED tells when the xa25 is on.

On the left and right sides, you will see the engraved nelson pass XA25 and PASS signs. They nicely reflect the two grooves carved out of the front plate. The back is straightforward too. It comes with the onset of RCA inputs, one of high-quality speaker wire terminals, speaker cables and the IEC input. Last but not least, a pair of robust handles make carrying the amplifier relatively easy. They are durable and placed strategically on either side, making it extremely easy to take the device around. The speaker cables make it easy to connect anywhere.

One thing you can expect from Pass labs is that they don’t joke around in terms of quality materials. This is why you can expect the best chassis and are top-ranked in the market, no matter the price. 

The inside

The real action is inside the panel of the xa25. I was really impressed with the pure Class A design used. And this is a construction that only uses two transistors per channel, yet able to deliver an incredible 25 watts at eight ohms. And 50 watts transferring into four ohms. That’s not all.  It’s class a design ensures that it can give out a current of 10-amp output too. This means the amplifier can drive many of the speakers we use at home with straining.

Other notable features of the xa25 worth noting include the damping factor, output noise level, and slew rate. Compared to other versions from the manufacturer like XA30.8, or XA25, it delivers a higher damping factor of 500 against the 150 from XA30.8. The noise level is lower, at UV: 50 against UV: 200, and a high slew rate of 100v/us against 50v/us of the XA30.8. The XA.8 series by Pass Labs are among the quietest solid-state designs the market can offer. And the XA25 features among the lowest of them all. Additionally, there are single-ended circuitry and less parts in the signal path.

In terms of sonic parameters, these factors mean the XA25 is a faster, more dynamic amp. The xa25 clearly offers the best transparency/clarity, and it exhibits greater control over low frequencies, thanks to its low damping factors.

Note also that the XA25 uses a qualitatively different transistor than other amps from the manufacturer. Nelson explains that “it is more practical to match a quantity of 150-plus-watt devices and run them parallel, which calls for resistive ballast for thermal stability…” The other types of higher power devices have been on the market long enough, and Nelson says he has been observing them. So, they decided to remove all the degenerative resistance from the output stage to create more sonic functionality. This requires the use of new bias circuits, which are in the model, and a limited number of other products.

Hook up

I received the XA25 with the usual first-rate packaging used by Pass Labs for all their products. I was using the amp with my audio production setup. My Tekton design speakers have been performing moderately with the XA60.8 monoblocks. I also had to put aside all the other amplifiers I use just to get the clarity that comes with XA25.

Other parts of the setup included a CEC-3 CD transport, Concert Fidelity – 040 hybrid DAC, a Linear Tube Audio Micro-ZOTL preamp, and Audio Archon power cords. I also needed, Running Spins power conditioner just to keep everything secure and safe. Xa25 amplifier is still DC coupled and has no frequency compensation. The result is faster, lower distortion for this amp.


There are very few simple-design amplifiers that can deliver the muscles and strength I witnessed with the XA25. My first selection came from the Jazz Pianist Ahmad Jamal “Jazz Book Records.” The xa25 captures the incredible piano accuracy of Jamal’s playing. The XA25 impressed me with its overall liquidity as music oozed flawlessly from my speakers. It displayed unique qualities, like no other solid-state amplifier in this price range, could.

Also, this is the quietest amp I have ever used. Every micro-detail was delivered with such clarity that I feel like part of the music. I tested with several other pieces, including the vocals of Steve Winwood, and it all came out as expected. It produced the kind of micro and control dynamics you can expect on a tap. When other bandmates joined, every instrument could be heard with clarity and exceptional sturdiness.

What I did not like

This amplifier is not a balanced design. This means you will need to use a single-ended RCA connector to drive it. Also, it’s very transparent that the XA25 stereo requires a reference-level preamp to work better. Lastly, using speakers with low sensitivity and impedance slopes will not give you the best music results.

Conclusion and comparison

The Pass Labs XA25 falls in the price range of $5000, which ins’t too bad for an xa25 amplifier. There is a line out amp in the same bracket that offers high competition. I can refer to Sanders Sound Magtech, which can drive any speaker. But it does not have as much liquidity. Another great alternative would be the Aesthetic Atlas. It is a little pricier, but it is a warmer amplifier. It also lacks the overall liquidity.

Considering these options, I can comfortably say the XA25 by Pass Labs is the best simple, high-end amplifier. It may not have all the best features, but it does offer incredible functionality for both new and experienced audio equipment buyers. We hoped this Pass Labs XA25 review helped shed some light on this product and be sure to checkout hometheaterreview com for more reviews on music audio equipment just like this pass lab review.