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Positive Feedback ISSUE 32
july/august 2007


pass labs

X1 preamplifier

as reviewed by John Brazier






Vertiy Audio Parisifal Ovations.

NuForce Reference SE monoblocks and Pass Labs X1 preamplifier.

Naim CDX2 and XPSII Power Supply with Sympostium Svelte Shelves and Phat Padz.

Full compliment of Crystal Cables CrystalConnect Reference cables, power cords, interconnects and speaker wire.

Wiremold/Naim Power strip.


In my house is a very attractive two chassis Pass Labs X1 preamp. Identical in sizes, one chassis houses the power supply and the second, the control unit. Simple layout and an easy to read lighted readout make for an uncomplicated functioning system.

Pass Labs have been around for some time and is well entrenched in the audio world. Even so, I have to admit that other than at shows and such, this is the first time that I have had the pleasure to spend some serious time with any one particular piece.

Thanks to the patience and accommodating Pass Labs (I received this unit last December, but to a move and other circumstances, it took way longer than anticipated to finish the review), I have had the pleasure of hearing it in two completely environments and with a few difference set-ups of my system. When I first received it, my listening room was 12 x 16, now it is 22 x 22. The preamp worked splendidly with the DeVore Gibbon Super 8 and my new reference Verity Audio Parsifal Ovations. It has also survived a couple of wire changes for fun and, when I moved in to this house, a power conditioner was found to be necessary—the sound went from "unconditioned" to conditioned by the Audio Magic Mini Stealth. As a side note, I forewent the supplied power cord for the Crystal Cable Reference power cord in the belief that one should maintain the consistency of the wiring in a system—now much more so after I have reviewed a full compliment of Crystal Cables.

To say I have had the opportunity to really evaluate this unit fully and in a multiple of "lay-outs" would be an understatement. With the relatively recent addition of the Crystal Cable Reference cables throughout my rig, my system has reached an unparalleled level of transparency. The X1 was the final stamp in defining this signature sound of my set-up.

Even so, I am please to report that the Pass Labs X1 does not have a signature or character of its own. Like the preamp I used before, the information just passes through unadulterated and free of influence. With either rock, classical, jazz, the X1 lacked any tendency to favor one genre over the other. Using any number of John Coltrane discs as an example, the X1 channeled the full spirit of the music a completely as the Naim CDX2 could offer as a source. The same can be said for Ginger Baker, Barry Green, and Diane Reeves.

NuForce recently sent me their "V2" version of the Reference SE amplifiers that I have been using as my reference for the past year or so. The details of my findings of that amp are in a forthcoming review, but without letting too much out, the X1 truly let the new sound of the V2 explode and fill my medium-large room (the improvements heard from the V2 are not subtle). Every minute and significant improvement in the NuForce was clear and noticeable. Nothing was in the least bit smoothed over or otherwise translated differently by the X1. This is the mark of a truly excellent preamp.

I dug pretty deep in pulling out of some favorites from years gone by; such as, Stacy Kent's Love is the Tender Trap. The X1 allowed Ms. Kent's demeanor and emotion to pass on and right out into the forefront of my listening room. I most often listen to just one track in particular, Comes Love. With the X1, I could all but see her big smile …scratch that, I could all but hear her big smile. The emotion of the recording was so effectively transmitted by the X1 that the music took on a completely new dimension, one where emotion and attitude owned part of the stage together with the music.

My experience in the past has been that subtle emotional cues are only sometimes picked up and conveyed to the listener. Hence, the listener is not effectively drawn into the music. The X1's capabilities altered that perspective. It has the knack of bringing out the musical elements that complete the whole musical event—not just the notes.

On Jimmy Scotts Holding Back the Years, the title track is presented with just enough detail without blowing it. Mr. Scott has a slight slur, which I had never heard in such a pure manner before, and as such, the X1revealed a convincing emotional cue. To my ears, nuisances such as that are compelling evidence of a real performer is in front of me.

In the lower frequencies, the X1 delivered a controlled bottom, only limited by the depth of the speakers. Regardless what is there, the bass is good, taught, and clean. The deep controlled voice heard all through Greg Brown's Covenant, is convincing and vibrant without any marked limitations.

The young Joss Stone, born and bread in England, has a soul voice like no other. Her first successfully commercial CD Mind, Body and Soul is actually her second release. Even so, this CD is considered by many as just a more refined extended version of her first release. These have been followed-up by 2007's release Introducing Joss Stone. Each disc has great vocal efforts, but, "Right to be Wrong" off Mind, Body and Soul, comes at you via the X1 with Ms. Stone's soft and soulful heart and an honest amount of edge and youthful sophistication. She sings of the fact that she is young and entitled to be wrong, and the X1 captures this dead on.

Then there is young Hillary Hahn, the 25-year-old violin virtuoso and her Edgar: Violin Concerto, Vaughan Williams: The Lark Ascending. Here the highs get as high as a tweeter produce. The X1 handled and presented Hahn in brilliant and convincing manner. The X1 placed Hahn in the midst of the orchestra, and when the time came, spotlighted Hahn while giving her room to breathe. All this while completely and beautifully maintaining the separation of the individual instruments.

Charlie Musselwhite has been playing his harmonica on the blues scene for many years. Until recently, most of his CDs have remained true to his blues roots. A recent release Sanctuary deviates just a bit by adding more modern technologies and themes. Shadow People has a haunting harmonica entrance to the tune. With the X1, the over all presentation was every bit "in the moment" as I could ask for. This whole track consists of a harmonica, bass, and a drum kit and did not have me wanting for more. Clear was the picture that Musselwhite intended for the listener to see.

I would like to add that the remote is a nice size and appears to be constructed from a hunk of aluminum. It is relatively intuitive and generally applies the same logic in adjusting the settings as the push buttons on the preamps faceplate.

With the absence of any criticisms, it is not a stretch to assume that I believe the X1 to be near the top of the price/performance ratio. For the money, I do not think you can do better, especially if your preferences are transparency in the sense of wanting the preamp to get out of the way and let the other components do their job. My set-up has been going through a major overhaul over the last couple of years. Circumstances have been such that I have been able to chase the level of performance that I did not think I could ever obtain. The last piece of this puzzle has been the selection of a preamp. With the X1, I did not hear the need to look any further for the "right" unit to fit within my set-up. I now own the X1. Just give it a listen you will be amazed at what you don't hear; you might end up owning one too! John Brazier


  • Gain: 4dB or 14dB

  • Freq. Response: -3dB @ 2Hz, -3dB @ 100kHz

  • Distortion @ 1KHz: <0.1% THD typical, 0.003% @ 2V

  • Output Impedance: 360 Balanced, 150 Single-ended

  • Input Impedance: 66K Balanced, 33K Single-ended

  • Output noise floor: -125dBV ref to 10V output

  • Dimensions: 2 @ 17"W x 3.5"H x 11.5"D

  • Weight: 46lbs

X1 preamplifier
Retail: $6000

Pass Labs
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