Review of the Pass Labs X350.8 stereo amplifier

I have been thoroughly enjoying my Yamaha NS5000 speakers since I purchased them in early 2020. They have truly amazing imaging and a natural tonality that lets you settle into the music and really be convinced of the performances you hear. I have powered them with older Bryston 4BSST amplifiers in mono mode. I briefly tested a single 4BSST in stereo mode and was extremely impressed with further improvement in imaging, resolution and staging (likely due to better impedance matching). But despite the great sound I was getting I did wonder how far I could take sonic experience.

Optimizing my front end with a Lumin u1 mini streamer (powered by a Keces P8 ext PSU) feeding a Audio GD DI20HE digital converter before going into my denafrips terminator dac certainly provided a fantastic source. I noticed when adding the lumin and agd devices a blacker background with more microdetails and holographic layering that was easy to pick up over prior solutions including direct USB to my dac, using an sotm dx usb DDC or with an SOTM 200 ultra (with sps500).

With the front end sounding great curiosity took over and I promptly sold my bryston monoblocks that served me well for over a year as well as a headphone to help fund my next amp purchase. After considering various brands and conducting endless research I settled on Pass Labs. They are a well respected and trusted brand that has a reputation for incredible build quality and incredible sound. I selected the X350.8 and this is the focus of my review.

Upon lugging the amplifier into my listening room with the help of my supportive wife I marveled at just how massive the amplifier was. Pictures online truly do not do the amp justice. If you are considering an amp of this size please do make some room! After connecting it into my system and hitting the front switch the legendary blue meter illuminated and the indicator moved to 60 degrees. I allowed for a 1 hour warm up. This was a demo unit as well so it was run in.

The amplifier was clearly incredibly well made. The metal edges sharp, the grooves milled perfectly. The heat sinks elaborate with their numerous thick angled tree like fins. The thick anodized ring around the VU meter was beveled and smooth to the touch and the VU meter extremely easy to read from a far. In standby mode a center blue LED above the Pass logo glows. Upon activating the center switch there is blue illumination on both sides at the 10 o’clock and 2 o’clock position.

Listening impressions
Starting with Anette Askvik - Liberty I noticed immediately the sound stage and ambient cues were spread further then the boundaries of my relatively small 12 x 16 x 8 foot listening room. Upon hearing her voice I was shocked at the staggering sense of her voice being projected forward in a 3d holographic way so as to seem to be in my mind. There was beautiful tonal purity as she sung and the slightest nuances of the saxophone were perceived well before I had in the past in my old system as it emerged from blackness and dynamically grew and projected organically into the room.

Houston Pearson - Sentimental Journey transported me to a smoky jazz bar as the double bass reverberated with texture and was easily perceived in the background on the left well behind my front wall. Houston’s saxophone had a beautifully accurate timbre and was once again absolutely holographic and projected in a way that it was virtually tangible in the room. The electric guitar imaged extremely precisely closer to the floor in the center and had an extremely distinct slightly muted tonality that I simply had not heard before. The clear delineation between the instruments with respect to the air and space around them as well as their unique tonal colours made the performance incredibly convincing. Cymbals had just the right amount of sparkle and resolution that allowed one to easily visualize the drumsticks tapping on them as they floated in the air well away from the speakers.

Made in heights - Slow burn is one of my favorite house songs and was represented extremely well. Well mastered music absolutely shines with the X350.8 where Kelsey Bulkin’s voice was incredibly smooth, liquid but filled with nuance and inflection. The panning of her voice had an incredible dimensional quality and it was clear this amp is not only a master of organic nuance and detail but has fantastic pace, speed and attack. Bass lines are very punchy, ti
ght and precise. Near the end of the song there is a segment with various chords being plucked and stretched to produce strange odd sounds and although an indeed strange part of the song I was absolutely blown away by how the strings seemed to be literally floating before me rendered in a holographic way that I absolutely never heard on my prior bryston amps. In fact the overall presentation had a dumbfounding depth in the sound stage that made the music all the more immersive.

Chris Botti - Ever since we met features singer Bridget Benenate is one of my favorite Botti tracks and was rendered in an incredibly intoxicating way. With this track I had perhaps the most transformative experience of all the songs I heard. It truly seemed the walls of my room and my system itself disappeared. Indeed there were moments where I forgot where I was or that I was trying to listen to music. Instead I organically became part of the experience. Botti’s trumpet shone with piercing dynamics and clarity and interestingly Bridget’s voice was seductive but pushed much further back then I had previously heard. Again the X350.8’s ability to elaborate an incredible sense of soundstage depth was on full display. This made Botti’s trumpet and bridget very distinct, in their own space yet they blended into a simply sublime musical experience and I was moved to tears.

Computer Magic - Cold Summer is a synthwave track featuring Danielle Johnson and her voice is simply addictive to listen to. The pulsation of the bass and reverb and decays of her voice swam across the soundstage as I envisioned a retro/futuristic blade runner-esque skyline. Again I was incredibly impressed with the X350.8s resolving ability of microdetails and its bass speed, and impact. This amplifier can move when the music calls for it!

I was immediately compelled to play one of my favorite tracks that always leads me to similar futuristic reverie. Vector loves - Neon Sky rain… upon playing it I was immediately shocked by the low level resolution and vanta black background from which emerged a subtle sound of static that hovered in the center of the soundstage. The static ebbed, flowed and crashed with subtle sci-fi waves as the electronic beeps and noises fluttered throughout the sound field. And when the bass line dropped giving way to the sci fi voice and whirring tech sounds I was again emotionally moved to tears. I have listened to this song 100s of times and I simply never been this immersed in it and transported to the reverie of being a hover vehicle cruising through a future of glowing signs and towers of technology.The combination of incredible transparency, air and speed was what made this track so potent.

Moving to one of my favorite flutists; the late Jean-Pierre Rampal and his Bach Partita and sonata for flute BWV 1030: Adante it was as if Jean Pierre was in the room. As an amateur flute player myself I was shocked with the beautifully accurate timbre and its microdynamics that truly did justice to one of the greatest flutists of all time. Only Jean-Pierre plays in such a powerful yet graceful way and this power, projection yet delicacy was perfectly captured by the X350.8. Trevor Pinnock’s harpsichord was precise, almost sharp but not fatiguing and he could be clearly placed in the soundstage and the complexity of his playing was easily perceived given the extreme resolution of the Pass + Yamaha handshake.

Malia - Magnetic Lies is a great jazz/pop fusion song. As the initial cymbals sounded they floated again around the soundstage and the bass was deep and tight. The perception of space and stage with each bass pulse was enormous. Malia's voice reinforced this effect and it was once again like the sound was simply in my mind and my speakers were actually not playing. Everything faded away and the deep, chesty quality of Malia’s voice took over. The way her voice faded with vibrato into a utterly noiseless background was incredible and served to pull you into the experience.

Throughout my listening I noticed the Pass labs amplifier had a tonal warmth and richness yet incredible detail, resolution and air. It was never fatiguing yet it was not dark, muted or rolled off in the upper frequency. Indeed Nelson has achieve a beautiful balance between nuance, detail and spatiality with an emotionally organic and musical sound.

One reason I chose the X series amplifier over the XA series was concern about excessive heat. Well the big X series amplifier gets very hot too so be sure to give it plenty of room to breath. My room became a veritable sauna unless the AC was cranked but when engrossed in the intoxicating sound of the pass labs amplifier this is a pretty acceptable trade off. The sound does improve as the amplifier warms and becomes more spacious, airy and tonally beautiful but even after 15 minutes of warm up the amplifier does sound fantastic. So if quick on and off sessions are what you are looking for I do not think this amplifier will disappoint.

This is also a very heavy amplifier and likely a two person process for setup so do have someone else to help. Occasionally there was a metal ‘clank’ sound. They may be due to metal expansion as the amplifier heats up but it was infrequent and did not interfere with the overall listening experience.

What can I say other than I am completely blown away by this amplifier's performance. I simply did not expect this much of a gain in sound quality. It excelled in every way I think about sound and I cannot think of any obvious downsides of his amplifier other than considerations about heat.
The Pass Labs X350.8 is a beautiful amplifier to look at and to listen to and in all ways outclassed the older Bryston amplifier. It excelled at producing a vast soundstage that went far beyond the walls of my listening room, had great dynamics, pacing and precision even with complex musical passages. The X350.8 presented music with a breath of warmth while still being exceptionally detailed in an organic way and produces precise holographic images that allowed me to experience and truly be part of the experience. The system, room and concept of listening to music fade away as you appreciate the sonic reproduction.

It is certainly not cheap but for this world class performance I feel it is worth every penny. I do wonder if there are more affordable amplifiers that can get close to the performance of the X350.8. However, I have no desire to explore this and in fact simply wants this sound to not change as it delivers sonic bliss. If you are shopping for an amplifier under $15,000 then I urge you to consider the X350.8. It paired beautifully with my speakers and my system and I imagine it would serve many other systems extremely well. It is clear Nelson is very deserving of his legendary reputation. I look forward to many long engrossing listening sessions!

Special thanks
I want to give a special thanks to Francis Chung at Toronto Home of Audiophile. He is extremely experienced (he has been dealing high end audio for over 20 years). He is kind, fair and very accommodating during my purchase. I strongly recommend you consider calling him for all your audio needs. His website is here: Toronto Home of Audiophile.
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