Pass Labs Xs 150 Monoblock Amplifiers Review

At this point it seemed worthwhile to try something a bit different, so pop and jazz reluctantly gave way to classical.  I find myself repeatedly returning to the works of Ravel and Debussy, in particular the performance of Debussy’s Jeux conducted by Cluytens on Columbia SAX.  Late at night, when the electricity is purer and less subject to the fluctuations in power that happen during the day, particularly in the summer, this performance, especially on the French blue label SAXF, can be magical.  In this instance, the strings are gorgeous and there is a believable impression of the hall.  I would not have thought that this piece would have been well served by the Pass amps; however, I was wrong.  These amps preserved everything that makes this recording special for me.  Next up was the Reiner war horse Mussorgsky’s Pictures at an Exhibition on an early RCA Shady Dog.  This piece was well served by the Pass amps with a level of dynamics and bass control that my resident Audio Note 300B’s cannot match.

It seemed like a good time to throw something more problematic at the Xs 150s, the Columbia 6-eye recording of Stravinsky Conducting Stravinsky.  This is a dry recording and the strings can be annoying.  With the Pass amps, this recording was as non-annoying as I have ever heard it on a really high end system.  Bass was outstanding, and detail on the chamber music passages was so absorbing that the dryness on strings and the dryness of the recording in general, were only occasionally annoying.

It seemed fitting to finish the evening with another Joni Mitchell album, Don Juan’s Reckless Daughter.  The reproduction of Jaco Pastorius’ bass was breathtaking.  The recording is by nature somewhat bright and transitory, and reproduction on these amps was brutally honest.  Joni’s guitar sound, a pick-up in an acoustic guitar, is bright and annoying, but the Pass amps do not unduly emphasize it.  The complex over-dubbing of vocal harmonies is very clean.  PRaT is fine.  This is essentially an honest and clear reproduction of a great, but flawed recording.

By this time I had pretty much established that I was dealing with a world class set of amps with no easily apparent weaknesses, which in some ways bettered my long term reference, the Kegon Balanced.  Consequently, the focus of my listening shifted.  From this point forward, the vast majority of my listening was relegated to vinyl.  The Bill Frisell is a piece that I return to on a regular basis, it is more musically consonant than it is a sonic blockbuster.  Here, it was musically enjoyable but lacked a bit of air and was a bit darker than I remembered.  I also remember the guitars being a bit richer.  The differences were subtle and certainly did not take away from my enjoyment. “Blue Nile” is very hard to reproduce without it sounding annoying because of the heavy use of electronic instruments.  Here, I think that what I hear is more accurate than with tube gear, very smooth with almost no grain in the synthesized strings.  Finally, on the Daphnis and Chloe, everything is there information-wise, not a single moment of overload or harshness even during the most intense/dynamic passages.  However, there is a feeling that something is missing .  The strings, winds and brass appear with shimmer, edge and almost a feeling of surprise from a deep, dark, mysterious soundstage.  The heads of the tympani are palpable.  This is the best solid state I have heard, yet, it still lacks that last bit of extension at the top, is a bit darker than life, with the very slight loss of harmonics.  I keep asking myself, am I really hearing the difference anything or is it only in my mind?  The Xs 150 is certainly in many ways, the best solid-state amp that I have had in my system. 

The speed of delivery for instruments and voices is stunning.  There is no hint of any distortion or noise.  Nothing in the musical presentation takes away from any other element.  The air, space, depth and apparent room ambience of the recording are palpable.  Each instrument has its own dynamic envelope which allows a pianissimo strike of a triangle to exist alongside a forte gong crash, with each instrument perfectly distinguished, each part of the musical whole, but also being appreciated as their own notes.  The amps rendered it effortlessly.   I cannot imagine that I would ever want more power.  The stage is three-dimensional, images are stable and placed believably on that stage, each surrounded by its own cushion of air.  Bass is powerful and at the same time taut, articulate and well controlled.  With my speakers, which each employ four 10-inch dynamic drivers to reproduce the range below 170 Hz —  there appears with these amps to be an extra half octave of extension at the bottom.  Noise is vanishingly low, grain is for all practical purposes non-existent.  Most importantly, these are musically natural and emotionally satisfying.