Pass Lab X350.5

Pass or not?

I think every audiophile has probably heard it before. A power amplifier’s job is to produce enough wattage to power the speaker. It should not add anything to the sound at all. But I think we all know that this is not true. This is due to the fact that there are many types of amplifiers around at the moment. From single ended triode (SETs) to high wattage solid-state amps, your choice is aplenty and all of them sound different.
Due to many choices of amps out there, matching amps with speakers are the utmost importance to achieve musical bliss. For example, if you own or like SET amps, you know that they need to mate with high efficiency speakers like horns. But if you own any other type of speakers, you know that quantity matters as much as the quality.

What’s with the Pass?

Pass range of preamplifiers and power amplifiers are very well known in these parts of the world. They started with the highly successful Aleph range, which is then replaced with the X series in the late 1990s that utilizes the patented SupersymmetryÔ circuit. The first example of this design is the Pass Labs X1000, which was introduced in 1998. But Pass did not sit on it’s laurels but continue to work hard to come up with a totally new design which incorporates both the X-SuperSymmetric and Aleph single-ended Class A circuit which is called the XA series range of amps.
With learnings obtained in building the XA range of amps, Pass has refined the design of the X series to come up with improvements that resulted with the X.5 series. The Pass Laboratories X350.5 stereo amp which is the object of this review embodies the design technology and refinements of the X series Changes include improvements to power transformers, paralleled high speed / soft recovery rectifiers, improved AC EMI filters, more paralleled power supply capacitors, increased supply RC filtering, refinements to the front-end input circuits, and the addition of single-ended Class A bias circuits for balanced single-ended Class A at low power levels
All of these changes bring the X.5 series closer to the sonic signature of the XA series amplifiers. The X.5 series feature the distinctive front panel meters indicating of the level of current running through the output stages that have long been the visual signature of X amplifiers. The X350.5 accepts both single-ended and balanced inputs. The X350.5 is rated at 350 watts per channel in 8 ohms

Pass me the amp

It’s no joke muscling the Pass amp into place. You need 2 able bodied person to carry the 150lb behemoth. Not a joke when the amp with so many sharp heat sinks. I was lucky as my wife helped me. Such a sport!
One thing that struck me is how beautiful looking the amp is. I know, I know. One shouldn’t be thinking a power amp as beautiful but I can’t help it. The blue light that comes into life when you turn the amp also happen to turn me on as well! I spend some time marveling at the craftsmanship in building this humongous amp.


Does it Pass the sound test?

I have spend many happy listening hours with my own Rowland 8 amp and am pretty familiar with the sound. After obtaining the Pass X350.5 from the dealer, I unhook my Rowland and played the Pass amp continously for more than 2 weeks before doing any serious evaluation.
Although the Pass has a rated 350 watts on hand, the first test cd I used for evaluation was vocals. The seductiveness of Ms London in Cry Me a River (Best of Julie London, Rhino R2 70737 S2 18810) is just plain marvelous. Makes me want to cry her the sea worth of water! Every breath and movement of her lips is there to be heard. However the details heard are not forced but rendered so effortlessly and truthfully that some might not believe that they are listening to a cd source with solid-state amp. The euphonic bloom that I hear from tube amp is present. It actually make my Rowland sound a bit lean in this department.
To ensure that the vocals are aptly reproduced not only with one cd, I also tried another favourite cd of mine, Belafonte at Carnegie Hall (Classic Compact LSOCD 6006). The same seductive touch-your-soul vocals are again demonstrated when I listened to Jamaica Farewell. I also wanted to bid farewell to Harry but not before I listened to other tracks first. For those of you who are familiar with this cd, I think the most important to note is that Harry tends to shout in certain songs. This is best demonstrated in Day O. And even though Harry was shouting, the size of the mouth is still well rendered and I did not experience any listening fatigue. But what is beyond my comprehension is the air surrounding Harry Belafonte when he sang Man Piaba. When Harry was singing about what he learned about the birds and the bees, I was learning about another wonderful thing aspect of audiophilia, air that I hear due to the reverberation of the Carnegie Hall. This air also seems to envelop my listening space, making me feel like one of the audience.
Listening to more dynamic songs like the titled track in Janis Ian’s Breaking Silence (Analogue Productions CAPP027) shows me another character of the Pass amp. It can differentiate every musical instrument perfectly with no smearing at all. The drums’ heft also did not affect the Pass one bit. But what’s great is that I find that transparency has improved a few notches when compared to my older Rowland 8 amp.

What about Pass with more dynamic music?

No one will buy the Pass X350.5 and not whack it, right? I proceed to listen to Get Over It in Eagles “Hell Freezes Over” (Geffen GEFD 24725). The intro of the electric guitar, followed by the drums shows me the great layering rendered by the Pass that is just excellent. The soundstage is not just deep but wide, probably slightly wider of what I got with my Rowland 8 amp. Pace, rhythm and timing is all there to be heard. Just want to make your dance.
To “torture” the Pass amp further, I turn to track 2 of Dadawa’s Sister Drum (JVC XRCD 4509 99592-2). The starting of the track is nothing special, just vocals and some drums. But as you listened further into the song, you will hear power the drum as it is being whacked. It was so powerful that I was just awestruck. All the time, what I hear is a well-controlled bass, no fuzzy outlines or smearing whatsoever. The soundstage is still well defined with great depth. I am not joking when I say that this is not a disc for the faint-hearted.

Pass the conclusion

Pass has done it again. It is never easy to design a high wattage amp that can sound delicate when it need be and also powerful when the situation warrants it. But with the X350.5, what you get is a marvelous amp that can combine both virtues. Many tube amp devotees will always say that many high power solid-state amps are dark sounding with a pinch of glare when pushed hard. The Pass X350.5 amp shows me that this is not so. What you hear is an amp that sounds neither like a typical solid state nor a tube amp. What I get is the best of both worlds without the disadvantage of both types of design. Have a listen. I promise that you will get hooked instantly. Don’t say I didn’t warn you! Now where is my checkbook?