This is a consumer review of the Pass X150 stereo amplifier, compared and contrasted w/Parasound Halo A21 and Krell KAV-400xi (integrated).

Review System:

Preamp: Arcam A75+
Amp: Pass Labs X150
Universal Player: Denon DVD-2910
Cables/Interconnects: Blue Jeans Cable 10 ga. speaker cables w/locking bananas; Interconnects
Speakers: Dynaudio Audience 82's (frequency response rated 25hz-25khz)
My ridiculously small room: 10' x 10' [I know I have broken all audiophile rules w/my choice of speaker]

I recently purchased the Pass X150 and had a 30-day, in-home trial. It is a 150 wpc amplifier that reportedly runs in pure class A up to 50 watts/channel. This is quite remarkable since most listeners never reach this level of power continuously. After the first 50 watts, it switches to class A/B operation. It runs pretty warm but I can touch the (large) heat sinks and not get burned. It seems even the fascia of the amp serves as a heat sink since it is sometimes warm as well. The front of the amp is very thick aluminum (?) on top of aluminum in a silver-gray finish. It is very utilitarian/masculine looking. Other amps may not want to pick a fight w/it based on appearance alone. The blue LED's indicating power/standby are a little annoying, if watching a movie, but can easily be covered (this is the original version w/o current meter). It's pretty hefty at about 60-70 lbs, for being the entry-level amp in the series. However, there is nothing entry-level about the sound.

THE BIG PICTURE

I tried to start this review discussing particular characteristics from bass to treble. But that just wouldn't be right; it is contrary to the nature of the amp. This is the defining characteristic of the X150; it has an overall sound of organic delivery and focuses on the whole of music. It doesn't favor any particular frequency range; in this way it doesn't seem to highlight any particular hi-fi characteristic. The presentation is of the music and that is this amp's concern. You may get better delineated bass from a Krell, which is brutal in the mids/highs (IMO). You may find more seductive midrange from tubed gear, which often rolls off the bass and highs. But consistency top-to-bottom, neutrality if-you-will, is this amps trademark. It will reveal the "character" of components upstream/downstream; this includes the recordings themselves.

Some may think this amp does hi-fi imaging/soundstaging. If by that they mean, it has a convincingly large soundstage and pinpoint imaging, they're right. However, if the recording isn't well sorted, that's how it comes through the X150, while preserving the musical enjoyment. On good recordings all of the placement cues are there, w/solid life-sized images and a walk-in-and-around 3-dimensionality. The stage is not forward (in front of the plane of the speakers), nor recessed (behind the plane of the speakers). It seems, once again, neutral; starting at the plane of the speakers and extending to the sides and back. It's stage is both wide and deep.

The X150 does have superior soundstage depth compared to other amps I've had in my system. More recently I reviewed the Parasound A21 in my system (all other components/accessories the same). I like the A21; it is an overall good performer, but I had reservations about transparency (compared to my 50 wpc Arcam integrated). Having installed the Pass amp my observations seem to be confirmed in this regard. Because of the Pass amps transparency there seems to be more of an invitation to walk through the soundstage and around the performers. I wouldn't say its like holography, per se, since the images are focused; however, the images don't seem "fat", for lack of a better word, as they did w/the Parasound. This may be the result of perceived added warmth w/the Parasound. On the other hand, the Pass doesn't give the impression of bleached/pale images as I feel Krell does.

Which brings us to tonality. If Krell is winter and Parasound Halo is summer, then Pass Labs is spring and fall. That's my kind of weather! It neither jolts you to tears of pain when listening to violins, nor makes females sound somewhat "fat". It is simply a refined and smooth sounding amp, that portrays tonal colors and shadings accurately w/o going to extremes. By smooth I mean, there's not a gritty/grainy characteristic to the sound. That happened sometimes w/my Arcam on its own at louder levels, probably due to clipping. The Parasound also is smooth like the Pass Labs, but w/the added warmth.

It seems like I've been beating up on Krell. So I just want to say I haven't heard better bass from another amp than the Krell. The detail and power in the bass from this thing was outright astonishing from the diminutive-sized amp. It does have the edge over the Pass in this regard. The Pass and the Parasound I thought were pretty comparable in the bass.

CONCLUSION

The Pass Labs X150 is a coherent, neutral, powerful, smooth, 3-dimensional, musically satisfying solid-state amp. This is the best I have heard in my system. I would specifically recommend it for those who want their systems to present music as a whole and be as neutral as possible (as opposed to those who like to dissect, or those who want an amp with added character). It does all of the hi-fi things one would expect from a dedicated amp, but in a civilized and even-handed way. I would recommend the Parasound A21 for someone who has a leaner sounding system. The Krell sound I think goes best w/a system that is a little warmer/juicier in nature.

These are all good amplifiers; but the Pass worked best in my system.

Also want to thank Mark at Reno Hifi, who sold me the amp; excellent customer service and included 3 free SACDs (to my surprise when I opened the package) w/the purchase and delivery was on-time; included 1 yr warranty.

I don't know the exact product model year; I believe these began production around year 2000.

-JBreezy5-

Great, clean power that is sophisticated and subtle.

There isn't really anything I don't like about this amp. Some have said it is on the cold side of nuetral and I can see that - but it is not an issue with my Signums which, to me, tend to be a little warm anyway. I wish it only cost 5 bucks but other than that - no complaints.

This is a great amp. I have it matched with Sonus Faber Signums and the x-150 really makes the Signums sing. The Signums, while not being too tough a load, do require some good, clean power to be thier best and the x-150 delivers exactly that. I replaced a Krell KST-100 with the X-150 and, compared the the x-150 the KST-100 is very noisy. The Pass betters the Krell in every sense except the low bass and is way way better in the mids and highs. I don't think you would have to have golden ears to hear that, compared the the Krell, the X-150 is cleaner, more consistant, better on a wider variety of music, and just nicer to listen to. The Krell KST-100 announces it's presence and says "look at me". The Pass just hangs out in my rack doing what it is supposed to do . . . play music. I have been reading the reviews on this site for years and, in my opinion, most reviews here are useless (everybody likes what they just bought). The only really interesting thing to me is reports about equipment matching which is why I am writing to tell you that X-150 + Sonus Faber Signums is a good match. The Signums are a 4ohm, 86bd bookshelf with 5.5 in woofer and silk tweater and I would expect other, similar speakers would also work well with the X-150. Cheers.

Similar Products Used:

Parasound, Krell

Revealing yet relaxed. Unruffled in every way

The X-250 looks nicer.

I've been involved in the hobby since '74. Owned and heard many a great amp. My favorites that I've owned are all Pass designed. Threshold Stasis 3, Pass Aleph 3, and now the X-150. It is so vastly musical and consistent on every type of music, that one never has to worry about throwing anything strange at it. I've used it with: ML SL-3, CLS, Verity Fidelio, and ProAc Tablette Signatures, with no problems at all (Aleph 3 can't drive tough load speakers needing big current). Of recent amps I like the BelCanto evo, but, it has trouble with the CLS's. The FPB's are nice, but not as nice, and cost a lot more.

Similar Products Used:

Krell FPB, BelCanto evo, Classe

musically engaging,excellent soundstage,dimensionality and space,inner details and life-like vocals

This is a musically engaging piece that invites one into an emotionally involving experience. I have auditioned Brystons,Mark Levinsons,Blue Circle,Bel and they are all excellent products but I was completely touched by the musicality and the ability to reproduce life-like presentations of the Pass X-150!!One can really hear the sonic details even at low volume levels without distortion or loss of timbre accuracy. Needless to say, I placed an order with the folks at CCA and I am eagerly awaiting it's delivery. If you enjoy musical presentations as well as accurate life-like presentations this will be the one for you. It plays music, engages you and makes you want to share the joy with friends and music-lovers.
I am keeping my CJ CAV50 as it is another outstanding amp- now I can enjoy the best of both worlds- both tubes and solid-state!!

Similar Products Used:

Conrad-Johnson, Nads

smooth, no fatigue yet remains dynamic and detailed

none

I am using two of these and biamping. I have the power of
the x350 but IMO the sound is better with the smaller amps.
Very musical amplifier and detailed without a hint of grain
or harshness. I had the x350 for about a mos. but found it
somewhat unforgiving with some recordings (maybe a problem
with the recording or the front end, I don't know). In any
case, the x150s work better for me. Highly reccomended especially if you want a sound that is neutral to maybe slightly warm in character.

Assoc equip.
Aragon Soundstage
njoe toeb 4000 CD player
PSB stratus gold i's
PS audio p300
Alpha-core Goertz MI 2 spk cbl.
Wireworks balanced y-interconnects

Similar Products Used:

Pass x350, Threshold T400, Pass x5

Detail, soundstage depth, overall musicality, good value

None

What can I say? I simply love this amp. I use a Wadia 850 to drive the X150 and my Audio Physic Virgos. I cannot think of a better match for my Audio Physic Virgos and the in combination with the 850 the X150 is stunning. Before I found the X150, I was considering getting rid of my Virgos. Using the McCormmack DNA 1 Deluxe with the AP Virgos just did nothing for me. I was similarly dissapointed when I auditioned the Levinson 334. However, when I heard the X150 with my speakers, I could not believe the difference. My speakers came to life and whisked onto the stage with the musicians. If you are considering a Krell, Levinson 334, Bryston 4B or similar amplifier, do yourself a favor and listen to the X150.

Similar Products Used:

Krell, Levinson, McCormack, Bryston

Build, strength of transistors, nearfield equivalency.

none apparent

The x150 is one of the best amplifiers made and among the best I have ever heard. I include it in the lofty company of the Cello Duet 350, Cello Performance II Amplifiers, Krell FPB 600 and the Jeff Rowland Model 112. A x150 has all the power you'd need to light up everything from very efficient loudspeakers like my Wilsons or Sonus Fabers to more power-hungry designs from Martin Logan, B&W and Revel. The industrial design is excellent. The build quality is even better.
On Stevie Wonder’s "Sir Duke" from ‘The Original Musicquarium Volume II’ (Motown), the opening horn riff is very possibly the best example of the Jeff Rowland Model 112’s two best attributes. On "Sir Duke," the horns simply jump forward into space, while retaining a warmth and musicality that is found on only a rare high-performance solid state amp. The Rowland shows its ability to handle more complex arrangements, as Stevie's voice is layered neatly over the horns, bass and drums.
There is no amplifier that I am aware of that delivers such a combination of virtues at such a modest price. The Nelson Pass line is, and has long been, a standard of genuine audio value in a high-priced, often inflated market.
Is the x150 worth the investment? If you own serious loudspeakers and are looking for a world-class amplifier to power them without a hiccup, then the answer is "yes."

Similar Products Used:

3 non-mono Krell fpb series, Jeff Rowland Model 112, Cello Duet 350, levinson 383 integrated

Transparency,Detail,Speed,Built Quality,Imaging,Beauty.

None

My search for a perfect Power Amp ended.This Amp is a truly High-End.
Design and built quality are superb.I look inside,and "SURPRISE"!!! the internal construction and circuit layout are a pair with X-350,and vastly superior than X-250
I fall in love with this amp.,and Highly Recommend to serious Music Lovers!

Similar Products Used:

Krell KSA-50(Vintage),Krell KST-100,Levinson 331,Pass X-250

I recently purchased the PASS X-150. This iamplifier is very good. It is crystal clear. It is well defined, very tight, lots of "slam" and has excellent soundstage.
My description of this amplifier -- Accurate!

My only complaints. It lacks a little bit of depth (fullness of sound), probably because it lacks a little bit of bass, and mid-bass. I would also like a very slight touch of warmth.

Admittedly, the systems I listened to might not have been audiophile quality, but I did compare the PASS to a Levinson 27 amp. and an Arcam integrated amplifier, and a Hafler 9505.

Klipsch KLF-30 and KG5.5 speakers.
Sony 20 ES CD Player
Classe Preamp. and tried direct CD->AMP configuration
DH LABS silver sonic BL-2 cables
PASS X-150 (unbalanced mode and balanced mode)

I've had the Pass X-150 for about two months now. I auditioned a pre-production unit from the dealer for about a week before deciding to purchase one. Prior to selecting the Pass, I auditioned a Classe' CA-400, a Bryston 7BST, and a couple of other amps as well.
The Pass X-150 was clearly superior in every audible way. Accurate, clear, and with a noise floor or -150db, you can literally hear a pin drop in the midst of the most complex musical passage. Previously indistinguishable sounds, in tracks which I've known well for years, emerge effortlessly from the depths of silence. The unit runs class A to about 80 watts per channel, and I've set the maximum output of my cd player to coincide with this output level from the Pass.

The unit has only two gain stages. There is no feedback. Build quality is outstanding (I've opened it up and marvelled!). Overall, this is an elegant, simple, industrial strength design and implementation of unparalleled musicality. Highly recommended as the absolute best in this price range. And best of all, the owner of the company, Nelson Pass, answers his own email and is very informative regarding the product.

The System:
Pass X-150
Wadia 830
Martin Logan Monoliths
Sunfire True Sub MK II