Pass Labs X 350 Amplifiers

X 350

350 Watt Solid-State Power Amplifier - 2-Gain Stages

User Reviews (12)

Showing 1-10 of 12  
Frank Walker   AudioPhile [Mar 04, 2013]

Let me start by saying that had a 250x pass lab at first and it's sound was nice , but with my 4 ohm Eggleston Rosa speakers I needed more juice. So going up to the 350 gave me a stately emprovement . I have Strativary Rosa cables all over that gave the 350 its way of sounding sweet ,smooth in the mids and free of grit , grain or glair. I prefer a more natural tone to my music so I bought a Bat vk5 cd player with a First sound preamp that is a work of art, that combindes power , dynamics and the smoothness that look for . Mr. Pass has a amp for many audiophiles that love there music, because you would be hard pressed to find a power amp out to class the Pass lab . This is a amp that you can love.

OVERALL
RATING
5
VALUE
RATING
5
jgm   AudioPhile [Jan 18, 2008]
Strength:

1) Neutrality!
2) Neutral
3) See #1 and 2 above, repeat.
4) Highly revealing of all other components in the playback chain
5) Pride of ownership
6) A way out of the endless cycle of upgrades (at least for power amps)
7) Extremely wide and deep power bandwidth
8) Suitable for all forms of music
9) Probably only a few speakers on the planet that it might not drive to full volume
10) a HUGHE bargain if you can find one on the used market

Weakness:

1) Big, heavy and warm
2) binding posts may not accept some stiffer speaker cables with spades due to carry handles on the back of the unit
3) forces you to re-examine the rest of your components since their flaws will be revealed

I heard one of these driving big Tannoy's when they first came out and the sound was captivating. I have been searching for one on the used market and found what I consider the deal of the century. This amp just doesn't have a signature that I can identify. After living with this ampfor several months, I now understand why some reviewers had difficulty describing how these amps sound. Stone neutral is the only way to describe this amp...easily qualifying as the most neutral amp I have yet owned. I purchased this unit as a freshly "refurbished" unit. I have had it for several months and I still have yet to find something beyond it's hulking frame to identy it. The one thing this amp does well (for better or for worse) is reveal the rest of the chain. This amp places everything else in your system clearly under the looking glass. The good and bad of such a revealing and neutral amp are obvious: it will force you to re-evaluate your playback chain and will lead, most likely, to more purchases as you realize colorations in other component you hadn't noticed previously.

What can be said about this amp's character? Limitless power. Bass is tight, deep, authoritative and limited by the loudspeaker (in my case, Acoustat Spectra 2's). The highs are again limited by yoiur source components and loudspeakers but is never strained, etched, glaring, or biting. The feeling is extended and relaxed. The midrange is as good as the rest of your system allows...here, the amp just has no character...it is just absent. And music - forget about it. If you like it, you play it and you'll love it. Percussion...human voice...piano...strings...rap...techno...full orchestra...rock...the amp loves it, all of it and you will too. Loud, soft...it doesn't matter to the amp, only to everything else in your chain. I have yet to find an instrument or genre the amp won't handle is if it weren't there.

The main problem with this amp is, paradoxically, a direct result of its best qualities: it is so neutral and revelaing that I hear to a greater extent the limtations (flaws) in my front end and in my speakers...and this will ultimately lead to replacement (more purchases). Moreover, I think I will be forced to chose even more carefully new components that provide equal neutrality.

Build quality is second to none. The amp does give off heat and is heavy, but you can move it by yourself if need be. The only real criticism I have is in regards to the binding posts. They are alligned in such a way that the rear panel carry handles will get in the way of some cables with spades (I had a very difficult time with my PS Audio Statement bi-wire).

Overall, a tremendous product and an absolute bargain on the used market. This is the kind of amp you get to never replace.

Customer Service

I have no personal experience, however, reputation is very good.

Similar Products Used: Classe' CA-301 and CA-101, Jeff Rowland Design Group (JRDG) Balanced Model 5 and JRDG Model 2 with BPS, BAT VK-200, CODA Continuum Stage 3.2, Mark Levinson No. 29, Counterpoint SA-220, Adcom GFA-5500 and Musical Concepts Modified GFA-555, Hafler XL-280.
OVERALL
RATING
5
VALUE
RATING
5
ash   AudioPhile [Jun 23, 2002]
Strength:

EMOTIONAL & HAUNTING.

Weakness:

I WISHED I HAD THE SPM OR BETTER STILL THE VAHALLA IN THE SYSTEM.

MY SEARCH FOR A AMPLIIFIER IS OVER.ABOUT 6 MONTHS I CAN.T FIND ANY WEAKNESSES.THE REASON FOR THIS REVIEW IS TO SHARE WITH PASS LABS OWNERS OF HOW TO GET THE BEST OF THIS AMP. OR ANY PASS LABS EQUIPMENT.ONE DAY MY AGENT IN SINGAPORE SHOWED ME PHOTOS OF PASS LABS IN THE DEMO ROOM WHILE TOURING THE FACTORY IN U.S.I SAW THE WHOLE SYSTEM WIRED UP WITH NORDOST CABLES.I QUICKLY WIRED MY WHOLE SYSTEM WITH RED DAWN INTERCONNECTS & SPEAKER CABLES.MY WHOLE SYSTEM OPENED UP AND THE FIRST TIME THE SOUND I HEARD IS EMOTIONAL & HAUNTING. I HAVE TRIED VAN DEL HUL SCS6.AUDIOQUEST DIAMOND.WIREWORLD SILVER ECLIPSE 3 ETC.ALL OF THEM AS GOOD AS THEY ARE CANNOT MATCH THE NORDOST CABLES IN A PASS LABS SYSTEM.

Similar Products Used: TOO MANY.
OVERALL
RATING
5
VALUE
RATING
5
Gerald Greenamyer   Audio Enthusiast [Oct 30, 2000]
Strength:

Most realistic sound Ive heard for 6000.00, beat the ML 335 which is also 250 watts but cost 2000.00 more, this amp has no electronic signature of its own, supreme bass, best of solid state and tube together, finally I am satisfied, I have to be the pickiest person for audio, that says something. Much closer to the X350 than the X150,just less power, use along with B&W Nautilus 803's and a Pass X1 pre-amp, Im in heaven.

Weakness:

None that I can dectect,any piece of audio is a compromise, nothing is perfect, but this amp is as close as it comes for under $8000.00.

just buy this amp, it does everything right, best under $8000.00, without a doubt.

Similar Products Used: Audio Research Mk100II and the Pass X150, ML 334, 335 and 336, variuos Krell amps, etc.
OVERALL
RATING
5
VALUE
RATING
5
David Smith   Audiophile [Mar 08, 2001]
Strength:

Transparent, dynamic, quiet, liquid, detailed, can drive 1 ohm no sweat.

Weakness:

Runs hot as H. Its heavy as H.

Driving Martin-Login Monolith III (hybrid ELS + sub). Bi-amping, Pass drives ELS panels, B&K drives subs. Sony 777ES drives passive preamp which drives M-L electronic crossover which drives Pass and B&K amps.
I listen at low levels for hours during the day on weekends, and on weekend nights, we often turn out all lights and let it crank to realistic volumes with primarily jazz, rock and blues music. The Pass has a big sound, which may be another way of saying that it is very dynamic. It is also extremely clear and clean without a hint of grain or grit. The M-L panels drop to under 1 ohm at 20KHz which has a way of shutting down lesser amplifiers (I have returned several big well known amps due to this), but the X350 is unfazed.
The resulting stereo image is wide and deep, the inner detail is awesome and the slam produces goose bumps in my medium size room. The sound is very similar to good tube amps - crystal clear mids and highs except the Pass has far deeper and tighter bass and any tube amp. Speaking of bass definition, I discovered a little secret of the X series amplifiers ...
I am an electrical engineer and I studied Nelson Pass's patents and circuitry very carefully. I noticed that, yes, there is not feedback at the output stage, and there are no DC servo loops but as a result, the output stage bias current and offset voltage can drift over time and temperature. I contacted the factory and obtained a service manual. I have o'scopes and DMMs all over my house, so I opened my (6 months old - purchased used) X350 and measured the Class A bias and offset voltage. Sure enough, they had drifted from the intended factory settings by more than 40%!! Since the amp runs very hot, I decided to allow it to stay on 24/7 in order to thermally stabilize - which took 3 days! Then my bias and offset adjustments that I made every 6-8 hours (for 3 days) started to settle down. On the 4th day, I did the final adjustment, tightened down the lid screws and sat down to listen. The bass was much tighter, the bass stereo image was much more focused and the very highest treble octave was a little more open. An obvious improvement, well worth the effort. This occured even though the B&K amp drives the subwoofer (150Hz crossover to ELS panels). So the biggest definition improvement was in the X350/ELS panels upper and mid bass region down to about 100Hz. WARNING! This adjustment should only be performed by a trained professional. If you attempt do this yourself, you run a very real risk of electrocution and blowing up your $9K amplifier! I might suggest that many of today's "zero feedback" power amplifiers and preamps could stand the same adjustment in order to maximize their sound quality.
I also found that huge wire is required by the big Monolith speakers, 4AWG on woofers and 8AWG on the panels. This results in full dynamics with no compression even at high volume levels.
I built a very sturdy wooden amp-table with wide carpet wheels in order to move this 125+ pound beast around in order to wire it up and service it. This table sets about 9 inches off the floor and allows the huge heatsinks to completely overhang so that they suck in (via natural convection) plenty of air.
The blue LEDs in the panel get a little old because blue is so very intense especially when all the other lights are out - and you can't just remove the LEDs (I tried) as they are actually part of the bias circuit!

Similar Products Used: Cary Slam-100, B&K Reference, Marsh A400
OVERALL
RATING
5
VALUE
RATING
5
Ward Dorrity   Audiophile [Mar 23, 2000]
Strength:

Beautiful, supremely powerful, musical, but not euphonic or theatrical. Conveys 'inner truth' of performance

Weakness:

Not the last word in subterranean low end slam

A $9K gamble -
Talk about taking a $9K chance. I bought this amplifier solely on the basis of the advice of a couple of audiophile friends of mine, and on the recommendation of Stewart Marcantoni of A Sanctuary for Sound in Port Orchard, WA dealer whose advice has proven to be consistently reliable and accurate. Two weeks after placing my order, the amp arrived on my North Idaho doorstep. The first thing you'll notice about this amplifier is that it's a brute: 150 lbs w/carton. You'd best have a friend handy to assist you with unpacking and placement. A sturdy hand truck is also a Good Thing to have, especially if you have to negotiate stairs.

A Homer Simpson moment -
Since I had ordered the amp with the IEC 20 amp power cord option, I hadn't reckoned that my conventional AC outlets were the wrong configuration for this type of AC cord - NEMA 5-20 outlets are required instead. Doh! So, I had to do a retrofit to my dedicated AC outlets. This inadvertent upgrade was easy to do and resulted in better quality AC outlets. Upgrading to higher quality outlets seems to have reduced the overall noise level in the system. Cheap tweak, come to think of it: $20 for four pair of these NEMA 5-20 outlets at your friendly Eagle hardware store.

Looks don't hurt -
The X350 is a gorgeous piece of industrial design BTW. Massive - and I do mean massive - face plate and fascia, with one Cyclopean meter dead center on the front panel. Lit up, the meter face assumes a beautiful brilliant blue hue, with the same brilliant Cherenkov-like hue spilling from the amp's ventilation slots. Sturdy Rack mount handles on the back of the amp, too - and that's another Good Thing, considering its sheer mass. Five sturdy but soft rubber feet support the chassis, making it difficult to slide on a smooth floor (just forget about carpet!). The composition of the feet suggest that there may well be some damping and isolation benefit there.

Initial impressions after 48 hours of run-in -
The X350 beats my old Krell KSA250S hands-down. There’s a far more ‘organic’ feel to the music, more ‘weight’ somehow. Scads of inner detail - you can actually hear the impact of fingers on keyboard on good piano recordings, for example. Voices are to die for - whole, deep, organic and real. Even without the lengthy break-in period recommended by other reviewers, the mids on this amp are breathtaking.
There’s a crystalline clarity up top that is more a reflection of additional information in the form of detail as opposed to a tilt towards the top. The five foot ribbon tweeters of the Magnepan MG20Rs are mercilessly revealing, but at the same time they are quite possibly the best high frequency drivers on the planet. At no time did they sound hard or harsh - unless that was present in the recording. There was no sense of 'solid state' hardness or the infamous 'MOSFET fog' heard in other MOSFET designs.
The X350 delivers a better presentation of the entire dynamic envelope - ‘smaller’ bits of acoustic information aren’t masked by larger events, so you’re actually hearing more of what’s there. And all of that is kept in perfect proportion up and down the dynamic range of the performance.
Some reviewers have reported a initial mid-bass emphasis that disappears after 200+ hours of run-in - I don’t hear it, and neither does my wife, Candace. I would agree with other reviewers in that this amp isn’t the last word in Krell-like low end slam and ultimate depth, but I have a feeling that it’s more a matter of the fact that the X350’s doing a much better job of sorting out low-end detail and definition. I'm just hearing more information in the low end than I did with the Krell. I can hear the transition from one low-pitched note to another, something that simply wasn't there with the Krell. Low-pitched timbres emerged with distinct identity where they were not evident before.
And then there's the sense of sheer, effortless power. The X350 exhibits a sense of utter and effortless control over the MG20Rs, and at any level. The 20Rs can be driven to ridiculously high levels, and the amp never loses its composure or alters its spectral balance.
As the X350 warmed up, the soundstage began to unfold and deepen. Placement side to side and front to back is nothing short of phenomenal.
Still, there’s something that I can’t really put my finger on when trying to describe what this amp does (or maybe doesn’t do). Candace may have got it right when she said that everything seems alive now. For me, it seems as if everything I listened to was somehow more compelling, more worthy of my attention. Perhaps it’s that the X350 allows more of the emotion and what we might call the ‘inner truth’ of each performance to come through. While there's nothing euphonic or theatrical about this amp, it somehow manages to come across as the most musical design I've ever heard.
Other reviewers have consistently said that this amp really takes around 300-400 hours to truly settle in. I can’t imagine how much better it can get, but I'm looking forward to finding out! The reality is that the speakers, the amp, the speaker cables and interconnects are all relatively new and are still 'settling in'. The overall presentation is becoming deeper, more articulate and more effortless - it’s as if the system is doing a slow dissolve and leaving just the musical event in its place. And that's what it's all about, folks.
Present system
ARC LS22 preamp
Pass X350 power amp
Classe CDP-1 CD player
Linn LP12 / Ittok V / Dynavector 10X4 turntable/arm/cartridge combo
Magnepan MG20R speakers w/XO20 crossover.
Cables and interconnects
Cardas Golden Cross interconnects
5' Electra Glide Speaker Glide mains (Dave Elrod's latest mods)
4 pair of .5 meter Audio Magic Spellcaster II jumpers (to go from the XO20 crossover to the MG20Rpanels themselves)
Electra Glide Fatboy power cables.
Bybee Signature Pro power purification.

Similar Products Used: Krell, Levinson, Bryston
OVERALL
RATING
5
VALUE
RATING
5
Richard   an Audiophile [Sep 11, 1999]

I have been living with the Pass X350 for about 3 months now,and I am extremely pleased. The best way of describing its
sound is supremely NATURAL. This is especially true with voices I am
familiar with from 30+ years of critical listening.
I am consistently astounded with
the honest and lifelike sound of John Lennon, Carly Simon, Joni Mitchell,
Carole King, Paul McCartney, Roy Orbison, Elvis Presely and other vocalists.
(If you can, get a copy of Elvis 24-Karat Hits from DCC -- a wonderfully
recorded disk.) The timbre of voices is as close to perfection as I
have heard.
This naturalness also holds true
for instruments, especially strings and brass. (I think brass is one
of the most difficult tests of audio reproduction, and the PASS really
excels here. Poor systems can sound like a telephone when
portraying the brass section of an orchestra or jazz group.)

The other wonderful quality of the X350 is the way it decongests
complex orchestral music, such as Ravel's Bolero and Beethoven's
symphonies. I can easily distinguish between separate instruments.
My previous amplifier (see below) tended to scramble
and congest mixed sounds.

About my system:
The introduction of the X350 to my system was a controlled experiment:
I swapped out my old amp (an Aragon 8008ST) and, for a while,
changed nothing else. I eventually switched to Cardas Golden Cross
interconnnects (from plain Cross). Golden Cross is magnificent.
I use a Threshold T3 preamp;
I sometimes switch to a Stax T1W tube preamp (see conclusion below).
My speakers are 1 year old Aerial 10Ts. (I use Cardas Cross speaker cable.)
My only source is a Meridian 508.24 CD player.

More about the X350 sound:
While the Aragon imaged nicely, I often felt like a central voice
or instrument was coming from a simulated center-channel speaker.
Not so with the PASS. The imaged sounds have a realism I cannot
really describe, except to say they sound as if someone is sitting
in the room singing or genuinely playing an instrument right in front
of me. The timbre of all sounds is far superior to the Aragon.
The bass is extremely detailed, the opposite of "one-note" bass.
(A Krell FPB600 through B&W 801 Nautilus had a deep and beautiful bass,
but voices seemed a little smudged. The PASS's bass is
very precise and quite satisfying.)

Operation:
The X350 benefited greatly from a long break-in period.
I left low-level classical music playing about 10 hours
a day for 3 weeks. At first
it had an overwhelming upper bass and slightly shrill sound,
but this entirely disappeared after the break-in, and the sound
blossommed magically, becoming perfectly balanced and smooth.
(I really wish PASS Labs had mentioned this in the user manual.)
It really needs 6 inches of clearance on top and to the sides.
It gets very warm, but not too hot to the touch. It raises the
room temperature 1 degree F (according to my digital thermostat).
It was no problem, even in a recent heatwave (using central A/C).

Conclusion:
The X350 is an excellent amplifier for intimate listening;
it conveys a compelling sense of realism and detail that
is often startling. Perhaps a big Krell or Levinson would
produce a bigger movie-theater/ampitheater type sound,
but that is not my preference, and this is not really natural.

I also find that the spatial details and
depth is better with my (tubed) Stax T1W than with my
Threshold T3. I plan to bring in a tubed Audio Research
preamp as an upgrade to test this hypothesis.

I am very satisfied with my purchase and would buy the PASS x350
again in a heartbeat.

OVERALL
RATING
5
VALUE
RATING
tom smith   Casual Listener [Feb 12, 2001]
Strength:

nice warm, detail and airy sound

Weakness:

big

Pass is much better in term of smooth and open with solid sound yet detail.
The system
marantz cd-7
Pass pre and power
b&w signature 30.

Similar Products Used: mark levinson 336
OVERALL
RATING
5
VALUE
RATING
5
J Yum   Audio Enthusiast [Sep 11, 2001]
Strength:

Accurate, dynamic, resolution, deep bass, quiet and transparent

Weakness:

midrange not sweet enough. resolution a little bit not in detail in midrange.

Equipment in use:
Pre: Sonic Frontier Line 3, tubes changed to Telefunken ECC88.
DA : PS Audio SLIII
CD : Marantz CD19
Spearker: B&W Nautilus 803, KEP LS3/5A Piano Black
Cables: Audioquest Exterme Clear, Taralab Air-1 and CARDAS Netural Reference.

I have used the amplifier from Nelson Pass for many years. Started from the Adcom 555 to Threshold T100 , T400 and then PassLabs X350. Since It is too great and nobody would sell it, I needed to spend also a year to book for it from 2nd hand market.

The 1st CD that I played with this amp was piano. I could hear the difference between X350 and T400 although the amp not run-in. I could clearly see how the pianist press his fingers on the piano any play the music. Very detail and accurate!! At the same time, the bass become more controled and more punch when compare with T400.







Similar Products Used: Mark Levinson 335, 336.
OVERALL
RATING
5
VALUE
RATING
5
David Lin   Audiophile [Jun 07, 2001]
Strength:

Dynamic, transparency, resolution

Weakness:

Too accurate

I have owned too many gears, my wife called me an "equipment-phile" instead. With Sonus Faber Extrema and Dynaudio Confidence 5, I can't enjoy music unless music are amplified grainless.
I am not a solid state person, so I knew shopping would not be easy when I ran out of power on my Sonic Frontier Power 3 (best sound/value tube amp on earth). First came Classe, it has everything I dislike about solid state - edgy top and thin midrange, music sounded coarse. Levinson was smoother every where, but music sounds "sterile" and no soul. Krell brought back the rhythm, but also added some annoyance on top and mid. McCormack was surprisingly good for the money, but reliability was an issue and factory was not helpful to correct my problem. Last came the Pass X350, the first solid state amp that does not remind me of solid state. It has incredible dynamic, coupled with SF Line 3 and Sony SACD player, so every listening session is a new experience. Bottom end is close to the best, but I am not a bass freak and even tube amps can satisfy me. What matters the most is top end; my ears have been spoiled by tube amps and Pass is able to reproduce that inner details without harshness or grain. But nothing is perfect and it also applies to Pass X350. Midrange can sound lean on some system, so careful system matching is required.

Similar Products Used: Krell, Levinson, Classe, McCormack, Bryston, Sonic Frontier, Audio Research, and some others
OVERALL
RATING
5
VALUE
RATING
4
Showing 1-10 of 12  

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