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Pass Labs Xs 300 Dual Chassis mono amplifiers Review

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Pass Labs Xs 300 Dual Chassis mono amplifiers


Midrange and treble

Sometimes reviewers will say that a component is extremely “unforgiving” of poor recordings. By this they often mean that the high notes are grating and/or the midrange sounds unnatural. At the other extreme, a reviewer may say that a component makes everything sound “pretty”, making the music sound euphonic and causing differing recordings to sound alike. Then there is the proverbial “neutral” component, which may indeed truly be neutral in some sense, but is also lifeless and uninvolving.

So, how do I describe the mid and treble characteristics of the Pass Labs Xs 300? The Xs 300’s mids and highs are beautiful, but certainly not euphonic. They are replete with detail and nuance, but are forgiving with most music. They are as close to neutral as I have heard an amp be, while still being very involving and satisfying. So how did they do that?

Let’s focus first on the treble. Solid-state amps do a good job of accurately reproducing the leading edge of triangles, bells, cymbals and other percussion instruments, replaying them with a staccato crispness. However, all you need to do is listen to a good tube amp to hear that the trailing resonance of those instruments is prematurely cut short, preventing the note from fully developing. The Pass Labs Xs 300 manages to capture both the leading edge and the decay. Imagine a really clean-sounding and fast tube amp that leans towards closer to neutral musical reproduction than other tube amps, but has a lot less noise. That’s the Xs 300.

Let’s turn now to the midrange. Many music lovers will tell you that this is really where the soul of a recording lies, especially recordings with vocals. The vocals on the 24/96 versions of the Beach Boys’ “Wouldn’t It Nice” and Van Morrisson’s “Astral Weeks” sound too “hot” on many systems, and are good tests for speakers and amplifiers. Now, I know that the Astral Weeks album is regarded as good recording, but to me the title song “Astral Weeks” did not do justice to Morrisson’s voice, overemphasizing it’s nasal quality in a way that you rarely hear on other Van Morrison albums. I obviously wasn’t at the recording session, so I’m not claiming I know exactly what Van’s voice should sound like when it’s reproduced. The point is that you can more easily compare audio components in the context of specific characteristics of a recording, since a stereo system’s biases often overemphasize or mask shortcomings in the recording. Playing Astral Weeks with the Nada handling the treble and midrange resulted in the “hottest” rendition of Van’s voice. The Nemo produced the most subdued version, creating an almost tube-like rendition on Van’s voice. The Pass Labs Xs 300 produced something in between, but also with a bit more detail and natural texture than the Nemo or Nada. In my subjective opinion, the Pass Labs Xs 300 did the best job with this recording, taking the edge off Van’s voice while still providing every detail and nuance of that voice.

The Persuasions’ rendition of “Angel of Harlem” on Chesky Records is a very excellent recording, and you can hear the Persuasions up close and personal, with a sense of being at a live performance. The Pass Labs Xs 300 sounded very musical playing this recording, as well as with all the vocals I played, and did so with extreme detail and nuance.

One reason I picked two of the Brandenburg Concertos as review music was the fact that I had box seats for the Chicago Symphony’s performance of the Brandenburg Concertos at Symphony Hall in November. I made a point of listening to Concertos 2 and 5 on my system the day before and the day after the performance at Orchestra Hall. The piccolo trumpet in Bach’s Concerto No. 2 was absolutely “real” in both my listening room and at the concert, with a purity of tone that was piercing but never shrill. Very impressive. In separate listening session involving just the Nemo or just the Nada, the Nemo made the trumpet sound very good, but did so in part by slightly muting the trumpet. The Nada, on the other hand, also made it sound good, but was a bit more analytical, losing the sense of the body of the instrument. The Pass Labs Xs 300 nailed all the details, combining the best characteristics of both the Nemo and the Nada. Admittedly, we are splitting some hairs here, but the difference was clear upon close listening.



The soundstage of the Pass Labs Xs 300 was top notch in all respects, and was the equivalent of the soundstage experienced with the Nemo and Nada operating together in bi-amp mode. That pairing of the Electrocompaniets has always given me a fabulously wide and deep soundstage, with excellent location of performers. However, when the Nemo or Nada were used alone there was a small but nonetheless noticeable reduction in the expanse of the soundstage, both in width and depth. I may not have noticed the difference if I was not listening for it, but it’s unmistakable if you pay attention, and in this respect the Xs 300 betters both the Nemo and the Nada used individually. This is very impressive performance, and the Xs 300 did not have any problem filling my 29-foot room width. Combine this with the detailed nature of the Xs 300 and you’ve got a very lifelike presentation happening in your listening room. To be more specific, the performers are stable and readily identifiable on the stage, each one clearly separated from the others. One reason for this is that system noise is nearly undetectable, thus eliminating the “wall of sound” effect unless it is intentionally part of the recording. The sound of the amps is about the cleanest I’ve heard, especially when used in conjunction with the Pass Labs XP-30. All this is accomplished without making the presentation clinical or “hifi”.

Finally, as you might expect from the discussion about the Xs 300’s bass performance, this amp is totally stable at any volume level. This applies equally to the mids, treble, and overall soundstage. Even at the ear-damaging levels the soundstage was rock solid.



The Pass Labs Xs 300 amplifiers offer the advantages of very high resolution, but not at the expense of creating an artificial sound. One of the great ironies of highly resolved recordings played on extremely resolving audio systems is that they often don’t sound natural or realistic. Some details, such as spatial cues, add to the sense of realism, while others detract from it. How can this be? I am convinced that it has a lot to do with how we normally hear live music. It is extremely rare to be able to hear every minute detail of a concert during live performances. When we hear such fine details for the first time we may be impressed, but sometimes by the fourth or fifth listen we start getting the feeling that this detail isn’t “real” or “natural”.

The Xs 300 is a very resolving amplifier, but nothing in the detail sounds artificial or takes away from the holistic presentation of the performance. One good test of this quality is “Mystery Pacific” by The Hot Club of San Francisco. The plucking of the lead and rhythm guitars and nuances of the violin were clearly brought out by the Pass Labs Xs 300, and in a very positive way. Rather than distracting from the overall performance, the details simply make the recording more palpable.

When listening to “Fortune Plango Vulnera” from Carmina Burana the size and ambience of the venue can be discerned. It’s also easy to identify each singer in the choir, but you don’t lose the power of the overall performance. On recording after recording I found that each performer can be appreciated both for his or her own performance and how it fits with the band, orchestra, quartet, etc. I personally regard this aspect of the Xs 300 as one of its signature accomplishments.


Comparison with Pass Labs X-600.5

Sonic memory is fleeting, but I regularly thought back to my review of the Pass Labs X-600.5 monoblocks. Those amps had excellent power and dynamics, and did a very credible job with subtle details, but didn’t have the nuance of the XA series amps. You had to choose between the extreme power and dynamics of the X series, and the more natural presentation of the XA series. The Xs completely blows away the distinction between the X and XA series, besting both in every category. The realism of the presentation, especially in the midrange, sets the Xs 300 apart from the vast majority of high-power solid-state amps, including other Pass Labs models.



As I finish this review I’m sitting in our home’s smallish glass and stone sunroom, which is an acoustic nightmare, listening to music on Linn Radio with an iPad Mini as the Internet radio source, played through a Wadia 171i transport and 151 PowerDAC Mini and an ancient pair of entry-level Klipsch bookshelf speakers. I’m doing this to put things back in perspective. I’m a person who enjoys music on many systems, both good and bad, because, well, I enjoy music. Too often we forget that enjoyment of music is why we are in this hobby. Leaving out the iPad Mini (which I use for multiple purposes and is thus not strictly a piece of audio equipment) the system I’m listening to cost me around $850, and I’m enjoying the heck out of it as I look out the East/South/West windows. So what can justify spending $85k on the Pass Labs Xs 300 amps? I mean, these amps are one hundred times as expensive as this entire system!

After spending several months with the Xs 300, the answer is easy: if you can afford it and are looking for iron-grip-down-to-Hades-yet-silky-smooth-and-highly-nuanced high power amps, these babies will take your enjoyment of music to an extremely high level. Even if you think you really want high power tube amps, you should compare the Pass Labs Xs 300 because there is a big chance that they will change your mind. Hell – even if you’re shopping for low power tube amps you should first hear what these amps are capable of just to get a point of reference. Any hesitation you have about the Xs 300 (other than the money and heat) will be based totally on your own personal taste – not because of any actual shortcoming of these amps. Very highly recommended in the cost-no-object category and a reference for what is possible with power amps.

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