Country of Origin
Reviewer: Srajan Ebaen
Financial interests: click here
Main system: Sources: Retina 5K 27" iMac (4GHz quad-core with Turbo, 32GB RAM, 3TB FusionDrive, OSX Yosemite. iTunes 14.4), PureMusic 3.02, Audirvana 3, Qobuz, Tidal, Singxer SU-6 USB bridge, LHY Audio SW-8 switch, Sonnet Pasithea DAC; Active filter: icOn Gradient Box 2; Power amplifiers: Kinki Studio EX-B7 monos, Enleum AMP-23R, Goldmund/Job 225 on subwoofer; Headamp: Cewn.Grand Silver Fox; Phones: HifiMan Susvara, Meze 109 Pro; Loudspeakers: sound|kaos Vox 3awf + sound|kaos DSUB15 on Carbide Audio footers, Audio Physic Codex, Qualio IQ [on loan] Cables: Complete loom of Allnic Audio ZL; Power delivery: Vibex Granada/Alhambra on all source components, Vibex One 11R on amps, Furutech DPS-4.1 between wall and conditioners; Equipment rack: Artesanía Audio Exoteryc double-wide 3-tier with optional glass shelves, Exoteryc Krion and glass amp stands; Sundry accessories: Acoustic System resonators, LessLoss Firewall for loudspeakers, Furutech NCF Signal Boosters; Room: 6 x 8m with open door behind listening seat
2nd system: Source: Soundaware D300Ref SD transport clock-slaved to Denafrips Terminator +; Preamp/filter: icOn 4Pro + 4th-order/80Hz; Amplifier: Crayon CFA-1.2; Loudspeakers: MonAcoustic SuperMon Mini or Acelec Model One + Dynaudio S18 sub; Power delivery: Furutech GTO 2D NCF; Equipment rack: Hifistay Mythology Transform X-Frame [on extended loan]; Sundry accessories: Audioquest Fog Lifters; Furutech NFC Clear Lines; Room: ~3.5 x 8m
Desktop system: Source: HP Z230 work station Win10/64; USB bridge: Singxer SU-2; Headamp/DAC: iFi iDSD Pro Signature; Headphones: Final D-8000; Active speakers: DMAX SC5
Upstairs headfi/speaker system: Source: smsl Dp5 transport; DAC: Auralic Vega; Integrated amplifier: Schiit Jotunheim R; Phones: Raal-Requisite SR1a; Active DSP speakers: Fram Midi 120
2-channel video system: Source: Oppo BDP-105; All-in-One: Gold Note IS-1000 Deluxe; Loudspeakers: Zu Soul VI; Subwoofer: Zu Submission; Power delivery: Furutech eTP-8, Room: ~6x4m
Review component retail: €5'150
Photos by Dawid Grzyb.
Passed out, over or up. When it comes to Pass Labs, we've seen all the passable puns. Today continues where this left off. Read it to paint the full picture; and appreciate why today is all about five years later. For me it means new room, new speakers, new active crossover, new subwoofer, new DAC, new USB bridge. All good things are six after all. The only items that haven't changed are my music iMac with Audirvana; and moi. But I can't really be sure that I haven't changed. Age, experience and taste are all moving targets. So when the opportunity arose to revisit the smallest of the Pass Labs stereo amps, I jumped at the chance to reacquaint myself with one that got away.
Photos by Dawid Grzyb. Use mouse-over loupe function; or right-click to open in new tab for full size.
Five years on, I listen to class A/B direct-coupled amps of very high bandwidth like Kinki's EX-B7 monos, Crayon's CFA-1.2 and Enleum's AMP-23R. Both upstairs/downstairs systems now anchor via subwoofer integrated by active analog outboard xover. That also precedes the main speakers with an 80Hz/4th-order Linkwitz-Riley high pass. In the smaller system, those speakers are mini monitors with isobarically doubled 4" Alpair widebanders plus ATM super tweeter. The sub is a 2 x 9½" Dynaudio.
Downstairs it's hybrid open baffles around a 6" SB Acoustic Satori dipole midrange with dipole Mundorf AMT tweeter mated to a ported 9½" Satori woofer in a big bass bin. The sub is a 2 x 15" cardioid/Ripol affair. How would the XA-25 slot in now?
Let's start upstairs. Here Enleum's 25wpc power seems perfectly equal but when relaxed to 1% THD up from 0.01%, the XA-25 triples its published rating whilst costing $1'000 less than the Korean. Also, its 800w/40A output devices are a different breed than Enleum's. Their smaller power supply is already down to 45 watts into 4Ω. The XA-25 keeps stubbornly doubling to 100wpc into 2Ω—200 watts peak—and claims stability into ½Ω.
Not all watts are created equal or accompanied by the same current. Finally there's class A vs A/B so always on vs switched transistors. That said, being already down 6dB at 80Hz given my actively high-passed mains, neither amp was tasked with bearish bass burdens. With those out of the way, how would the remaining bandwidth react to swapped drive?
Before we find out, one more bit of confessional housekeeping. These small metallic widebanders are lively types which suits my mostly low SPL in this room perfectly. However, after a power-line upgrade to Akiko Audio's Corelli and a DAC upgrade to Cen.Grand's best DSD1'024 deck, overall liveliness had grown just a bit too fresh at times.
Rather than DAC direct through its analog ladder-on-a-Muses-chip volume, I'd inserted Vinnie Rossi's L2 Signature linestage fitted with my favorite Elrog ER50 power triodes. Run in grounded-grid mode without output transformers or coupling caps to be of exceptional bandwidth, this insertion injected the desired textures which the decisive uptick in overall resolution handled without any clarity confusion. Going in I assumed that with the XA25, I could probably remove the L2 and arrive at very equivalent sound. Now we've pegged my hardware and wetware scenario to key into sonic changes.
As it turned out, the Enleum/Pass game was one of core steadfastness against peripheral redecorations. Yes the XA25 was darker, moister, chewier and softer; but only at doses homeopathic enough to not upset my overall balance of tone over incisiveness. That's a key decision of system tuning. In car terms it weighs acceleration and comfort. Between the outermost polarities of a sedan that drives like a waterbed on wheels versus the pared-down two-seat racer which telegraphs any rain groove with its 'sporty' suspension lies a vast realm of degrees. Except for hifi radicals, that's where the great majority of listeners live. It's in the between zone where most find their ideal mix of speed and curves. For my tastes Enleum previously Bakoon Int. set that ideal balance. They just don't deliver sufficient current to do right by my downstairs Qualio IQ. So whenever I cross paths with people who love Enleum's sound, I inquire whether they've met anything alike; just with more useable power. Could I have simply asked the me of five years ago? I began suspecting as much by how ideally the XA25 bedded in upstairs without asking for any tweak-based counter steering.
I'd only know for sure once the XA25 hoofed downstairs to replace 250-watt Kinki EX-B7 monos as my high-power Enleum alternates. There the AMP-23R gets plenty loud but with insufficient control over the dipole 6-inch Satori cone. Using the same Exicon lateral Mosfets just many more of them, the Kinki amps on those loads are demonstrably better. Would the XA25's low-Ω stability and 'super' transistors follow suit? I'd know soon enough. Just then I was enjoying what it did for the isobaric SuperMon Mini. Even Chai Baba the lounge leopard had snuck in to exploit a temporary sun spot on the carpet. Quite unlike my assumption that I'd have to pull the direct-heated triode preamp to compensate for classic class A warmth and mass, the XA25 demanded no such thing. Percussive skin slaps and cymbal tickles retained their splattering acuity and steep rises as that sharper bite of highly damped transients which crack or tick without bloomy follow-up. Göksel Baktagir's qanun strings on a live DJ session with the Hakki Bros. were properly piquant and zingy whilst the counter clarinet sounded appropriately reedy and watery. Again, the shift between amps worked at the sound's periphery to not dislodge the core.
Whenever that's the case, the change registers in the moment to quickly elude attention because nothing fundamental keeps rubbing against our status quo to shout 'wrong'. Once I'd transitioned to this after state of full sync with the only marginally new, the only aspect I could still point at with a good degree of certainty was the XA25's greater tonal fruitiness. I like how suggestive that word is of plump juicy vegan fleshiness redolent with natural sugars that intermingle with tart vibrant acids. It's very different from bottled jams that have boiled their fruits in 50% sugar for cloying sweetness. The XA25's tonefulness suffered no such sugary artifice. Over the class A/B Enleum, it simply felt more deeply hued yet still fully capable of peeling out sounds of inherent piss and vinegar. Put differently, if the XA25 stayed on, I wouldn't miss the AMP-23R. Though not identical, the Pass in this context was similar enough—even down to the most minimal of push/pull outputs—to displace our far smaller resident, no tears shed but money saved. How about heavier downstairs lifting to formal status as a legitimate Enleum stand-in with more real-world power? Again, not all watts come with equal current. Not all watts behave the same when impedance sinks to new lows and power supplies begin to choke.
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