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Review: Pass Labs X250.8 power amplifier

The equipment upgrade path in my household steepened in late December of 2014. I thought I was in shape, but I’ve been panting. A lot.

I’d been using a Parasound A21 power amplifier for the past couple years. Before that I had a 7.1 Marantz home theater amp, the MM8003. Previous to that, a craptastic Denon AVR887 7.1 receiver. Going further back — oh yeah, there was that Adcom five-channel amp/preamp combo that I got cheap because it was pre-HDMI. The latter has outlived the Denon doorstop by about five years, by the way. It’s still seeing active duty in our conference room at work.

ANYway…I had strayed from two-channel stereo, seduced by all those 5.1 DVD-A releases I saw on Amazon.

The Parasound was good, at first. It drove a pair of Paradigm Studio 100 v5s more than adequately. I felt like I was getting back to my two-channel roots.

Soon after I’d bought the A21 used on Audiogon, I began going to audio shows, and listening to systems in hotel rooms. These were settings as incongruous as they were …un-optimal. Loud music door-to-door, no soundproofing between small, boxy rooms … and over half the music I heard coming out of the doorways made me cringe. I’d walk through the floors twice: the first time, listening for some artist I could at least stomach for a song or two, and visiting those rooms — and then going into rooms that had equipment I was interested in no matter what was being played.

I noticed that a significant number of otherwise-diverse setups had a common element — an amplifier made by Pass Labs. Sometimes those rooms weren’t even playing Diana Krall, or Stevie Ray Vaughn, or Dire Fucking Straits. I took this as a sign.

A rather grainy iPhone shot  of the Pass labs room at CAS 2014

A rather grainy iPhone shot of the Pass labs room at CAS 2014

I saw lots of Pass monoblocks, like at Cookie Marenco’s 2013 California Audio Show Blue Coast live DSD recording session with Alex de Grassi. Sometimes Pass amps were driving six-figure Wilson speakers, or top-of-the-line Sonys. At CAS 2014, Pass had its own tiny room, with XA60.8 monoblocks and Tannoy coaxials in disproportionately large custom cabinets, with source material provided by a vintage Technics turntable.

Almost every system with a Pass Labs amp sounded great, or at least interesting. Even in a hotel room, Pass easily stomped my humble home Parasound setup. I’d go home and listen to it with the highest-resolution files and the best LP pressings I had, and grumble.

The A21 had volume, but when I cranked it above 75db or so, the music took on a hard glare that became fatiguing after fifteen minutes or so. Half of what I play is modern classical, and the violins and pianos sounded…digital, even on vinyl. On live albums, when the audience applauded, it often resembled rain on a tin roof instead of a few hundred people putting their hands together in a nice theater.

When I first bought the Parasound, I’d sit in the dark and listen to old and new music for hours. But somewhere along the way the amp lost its allure, and the edge and grit would get to me, and I’d multitask. I’d grab my laptop. Play with the cat. Fidget. Go into the other room and watch TV.

I’d lost the focus that used to motivate me to pull out LPs I hadn’t listened to in twenty or thirty years.

IMG_4504I realized I had been in denial. I had a amplifier problem.

My solution was to procure a slice of the Pass Labs amplification pie and, last October, I resolved to quit drooling on the window of the bakery and do something about it.

At CAS 2014 — in the room with the Tannoys and the Technics — Pass Labs’ Kent English had given me the business card of Mark at Reno Hi-Fi. I contacted Mark via email and told him what I had, and what I was looking for. He was patient, friendly, responsive, accommodating and professional. I imagine he still is. Over the next three months he humored my hemming, hawing, and hedging. He encouraged me to take my time. He didn’t try to upsell me, or talk me out of my preamplification plans (which involved Zesto, not Pass). Other than my ninny-esque indecision, the process was a pleasure. As Vonnegut would say, everything was beautiful, and nothing hurt.

In December I purchased a demo unit under full transferable warranty; Mark told me it’d had about a month of use. It was a Pass Labs X250.8 stereo power amp. Why not monoblocks? In addition to, um, budgetary considerations, I didn’t think I had the necessary air conditioning for them — and I was going to my hands full fitting the one chassis in or near the rack, as it was.

A very large box arrived on January 2nd. Timmyhead, our 9-month old half-Bengal adolescent, donned his customary mantle of Box Inspector.

I’d been told to have another person handy just to extract the 250.8 from its substantial packaging. Nobody was around or available, however (“hey, good buddy, want to come over on the day after New Year’s and help me lift an amp out of a box?”), so I decided to go solo. In the specs we’re told the boxed weight of this particular Pass is around 120 lbs. My physique is not exactly what you’d consider … burly. So you figure out how I got the amp out of the carton, the plastic wrap off, and the beast onto the dolly I’d so cleverly placed in front of the rack. Or you can just ask the disc material between my L4 and L5 vertebrae (you don’t want to sit down next to my vertebrae in a bar, let me tell you. They’ll bore you for hours. You’ve been warned).

Backing up

The steel posts on the Mapleshade rack are maybe 3/8ths of an inch wider than 19″. Guess how wide the 250.8 is? This is whatcha’d call your basic close tolerances. I had to gradually slide the amp off the dolly and onto a 2″ maple plinth suspended on IsoBlocks. So I was scrambling to the front of the rack and pushing the 100+ lb. amp onto a wobbly wooden platform, then stumbling back behind the rack to pull the thing through an impossibly small horizontal space without scratching the handsome black anodized heat sinks. Without the handles placed so thoughtfully in the back panel, this would have been impossible. As it was, it took about 10 minutes to gently wrestle the amp into place, then reposition the groaning IsoBlocks (soon to be replaced with Stillpoints Ultra SSs).

It is easier to pass a Pass Amp through the eye of a needle...

Then I went outside and cooled down. Changed my sweaty t-shirt. Fed the cats. Grabbed some water. Caught my breath.

Hooking up speakers was almost easy (as easy as hooking up speakers ever is. I only cussed three or five times). I love the ratchet binding posts that prevent over-tightening spades. Spades, not bananas. Those handy handles conveniently doubled as torque-relievers for my new, thick, stiff and somewhat… disobedient Acoustic Zen Absolute speaker cables.

I made sure everything was secure, plugged the amp into the wall (no power conditioning), and pushed the oversized beveled metal button on the front panel.

The meter glowed in its very Pass-like fashion.

There was music.

The amp went through some interesting changes over the next two weeks. I wasn’t certain if the previous owner had really broken it in. The audiophile cliché invoked for the sound during that break-in interval is often polite. I understand the concept. The X250.8 sounded like it didn’t want to piss anybody off, especially at high volume. That said, it sounded reasonably good out of the box.

IMG_4532Then some weird stuff happened.

After about four days, following the addition of some new XLR interconnects and the swapping of certain source component power cords, the sound coming out of my new amplifier suddenly resembled that of a chrome-dioxide cassette being played through a Kenwood receiver and a pair of circa-’78, hand-me-down Utah 3-ways (my particular pair had candle wax dripped down on the all three drivers on the right speaker. What, yours didn’t?).

Inoffensive? Un-dynamic? I’m talking peevish.

“Who are you and what have you done with my X250.8?” I asked the glowering blue-meter’d ogre at the bottom of my rack.

My speakers, then about 12 days old, are Acoustic Zen Crescendo Mk IIs. They were still breaking in, too. I realized that it wasn’t just the new-ish amp.

I’d also changed interconnects, power cords, preamps, speakers…pretty much all over the same two weeks.

My system was a newborn baby with an upset stomach, and was taking it out on my ears like a colicky infant on a packed 737.

A couple days later, though, the amp really settled in and made itself at home.

It knew where the coffee and cereal and vodka and good towels were. It might have filled the bird feeders in the backyard and watered the orchids if I’d asked it nicely. I’d left it powered up for a week straight, as suggested (can’t wait for my electric bill next month) and the sound began to resemble what I’d heard at various CAS hotel rooms — only better.

It’s now been almost a month since its arrival, and everything that was new then is now broken in. How is it sounding?

IMG_4535The 250.8 is a stern taskmaster or, at least, some variety of benevolent dictator — with the right source material. Today I played a 16/44 CD rip of Bill Nelson’s 1981 album, Quit Dreaming and Get on the Beam (Cocteau JCCD16). The songs were and are wonderful, but the CD was from that mid-eighties era when, I believe, compact disk mastering meant shoveling the LP two-track to aluminum and plastic as quickly as possible. The sound was just plain bad. I kept turning it louder, for some reason. Shrill, strident, high-midrange-y… yuck. The 250.8 shook its head, rolled its eyes, and played what JRiver and PS Audio’s DirectStream DAC threw at it. No sugarcoating.

Then I played the 24/96 .wav of A Winged Victory For the Sullen’s Atomos. On my old system, it breathed. Well…at higher volumes, it sometimes wheezed.

Audiophiles like to talk about the quality of “air” in an amp’s sound. It’s shorthand for a sense of space within the soundstage where high frequencies dwell. The 250.8 possesses air. Maybe that’s not the word. It caresses air, and the giddy feeling that results from a serious listening session actually makes me believe that the air might be a little thinner in my living room since I coaxed the thing beneath my rack.

Sitting in the dark, listening to AWVFTS’s Atomos in high-res via the Pass was like hearing the band play live at 15,000 feet.

Due to some in-progress turntable/preamp upgrades (phasing out a Clearaudio Concept MC and awaiting delivery of the new VPI Classic Signature, plus a cranky tube or two in the Zesto Andros 1.2 phono preamp), I haven’t spun as much vinyl as I’d like through the Pass. The dozen or so things I did play during the break-in period showed more than mere promise, even on a 2-year old Concept turntable. I’ll go into the amp’s relationship with analog in a review of the Zesto Leto/Andros combination and Acoustic Zen Crescendos sometime soon.

I could parrot a bunch of stuff I’ve read online about class A/B amplification and bias and distortion and feedback and harmonics and try to convince you I really know what I’m talking about. I could raid the audiophile glossary for terms like “fast transients” and “warmth” and “transparence.” I’m not gonna bother. I reserve the right to do so in the future, mind you, but all that stuff just sounds dumb when trying to describe what Pass amplification does. One term I might parse is “detail.” With the X250.8 there’s detail, but there’s also texture, which trumps the bejesus out of detail every time, sorry.

There’s no tubes in the massive chassis, but the sound coming out of it is…tube. Without tubes. Tube mids and highs without the startup/shutdown thump, or microphonics, or hum. Tubes without the wear-out factor.

(I’d like to say it’s like tubes without the tubes heat, but I have a feeling this summer may have me sweating those words).

IMG_4519I’ve been sick with the flu for the past week so I’ve had lots of time to contemplate and philosophize and listen to music. Do I have a developing ethos about music amplification in the personal space? Sounds kind of exhausting, this personal-ethos development regime, but the old saw about iron fists and velvet gloves comes to mind. I used to think amplifiers just needed to make noise, be loud, not trash your speakers… y’know, that sort of thing. Over the past couple years I’ve really began to value how quiet an amplifier can (and should) be. Pass’s grasp of the solid state platform yields the blackest, most starless silences — and masterful bass control that renders such lazy adjectives as “taut” as so much faint praise.

I always wanted to get to the point where I could close my eyes and not really tell (or care) where the speakers were. I can’t be certain I’ve arrived at that point just yet, but the Pass Labs 250.8 is making the high-altitude journey very alluring.

It’s good, this compulsion to just sit and listen to music again.

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Other music used in this review:

Bernard Szajner Visions of Dune LP (inFine iF1029LP)
Harold Budd The Serpent (In Quicksilver) LP (All Saints, Cantil WAST039LP/181)
Brian Eno The Shutov Assembly LP (All Saints WAST032LP)
Interior Interior LP (Yen Records YLR22002)
Arcangelo Corelli Opus 1 & 3: Church Sonatas The Avison Ensemble SACD (Linn Records CKD414)
Mark Mothersbaugh ‎”Chechi” from Muzik For Insomniaks Volume 1 CD (Enigma 7 73365-2)
Neil Young On The Beach DVD-A (Reprise 9 73945)
Arvo Pärt Da Pacem Estonian Philharmonic Chamber Choir, Paul Hillier 24/88 .AIFF (Harmonia Mundi, via HDtracks)
Various Artists Look Again To The Wind: Johnny Cash’s Bitter Tears Revisited 24/44 .AIFF (Masterworks, via HDtracks)