From Stereophile's review of the XA25 we learn that like the XA-30.8's published 30/60wpc spec which scales comfortably to nearly triple 90/150wpc into 8/4Ω when THD relaxes to 1%, the smaller amp's 25/50wpc rating then reads 80/130wpc. Or as John Atkinson commented, "… it appears from the shape of the traces in these graphs that Pass specifies the XA25's power as when THD+N is close to 0.01%." To paint the connection between available power and distortion with an example from that other part of town, consider the German Audio Valve Baldur 300. It's a tube mono with 10 x 6AS7G power triodes per channel. Its peak power is a massive 300 watts. At 1%THD it's a still mighty 240. At 0.3%THD we're down to 100 watts. If we wanted half that distortion, we'd end up with just 10 watts. Yet 0.15%THD would still be a decimal point higher than the 0.01% which JA measured for the Pass. And that makes 25 not 10wpc, does so with less noise, lower output impedance and sells for $5'150 not £22'000. Strong talking points for transistor lovers.

In his review Terry London reminds us that versus the XA-30.8, the XA25 increases damping factor from 150 to 500, lowers output noise from 200µv to 50µv and doubles slew rate from 50v/µs to 100. Finally Stereophile shows a 10kHz square wave with very short rise time and no overshoot or ringing. Clearly the XA25 has some impressive figures going for it. In the same or at least next breath, we admit that none of it tells us what it sounds like. For that we need ears. Accompanying hardware for my first auditions had our then usual suspects: iMac FusionDrive digital transport or Soundaware D-100 Pro SD card reader; Aqua Hifi discrete R2R DAC; Wyred4Sound STP-SE II preamp; Audio Physic Codex speakers; and for first contrast our XA-30.8.

The two above stack shots show the XA25 to be narrower, lower and shallower than the 30.8 so more compact in all three dimensions. It doesn't show how much less that torques the lower back. Age becomes inversely proportionate to joy over raw component mass. If something must be big and heavy to work—class A bias at significant power pretty much dictates it—one accepts the fact that reality bites. But size for the sake of size or to impress anyone with certainly dissipates as motivator. On the lumbar score the XA25 had the obvious advantage. Having run the XA-30.8 over its XLR inputs for a while, I now had to revert to RCA to keep comparisons simple. On the matter of balanced inputs, the XA-30.8 has the edge.

For thermal readiness, both amps had 40 minutes of idle before I cracked into tunes. First up was Mayte Martin's Al Cantar a Manuel. It marries high production values of guitar, violin, bass, drums and cajon to vocals which seem to expose the uvula, that wiggly little worm inside the throat. Here the XA25 managed an unexpected troika of attributes. Tonally especially in the vocal band it was slightly fruitier than the XA-30.8. Microdynamically it was clearly more expressive like a faster circuit. This was particularly evident on Mayte's voice. It scaled more dramatically so felt bigger. When bass and drums kick in to suddenly light up the soundstage in its outer quadrants, their contrast ratio relative to the guitar, violin and singer which were already on was higher.

With the XA-30.8 in my estimation being slightly dark, bassy and dense, the XA25 stirred in some quicksilver. The mean trick was injecting quickening without diluting the tone density and chunkiness I adore in our stable mate. Typically so-called fast amps like our 1MHz LinnenberG Allegros light up. It's as though to go so fast they must shed some tone mass or physicality. Decisively the XA25's uptick on the accelerator did not. The core beneficiary on this first track was higher dynamic contrast within the range of a first-rate singer, i.e. not the intense climaxing of symphonic peaks nor the envelope of a heroic tenor at his best but rather the emphatic expressiveness within a non-operatic melodic arc. Audiophilia calls that microdynamics. As the XA25 showed, those needn't be so micro.

For my second pass I transitioned to virtuoso Arabian chamber Jazz compliments of The Khoury Project's Revelation, a prior year's favorite find. It showcases violin, oud and qanun against bass, hand drums and percussion. Again the XA25 took the lead on dynamic range. It also notched up the frisson or electrifying aspect of drum hits, cymbal slaps and wooden cracks though neither amp peeled those from the surrounding thicket like our ultra-bandwidth LinnenberGs. Ditto for harmonic envelope. The Middle-Eastern violin played as modal fiddle and the region's lap zither can scratch and splash. It takes a leaner amp with more treble exposure to maximize those coarser rawer aspects. By implication such amps reduce some tonal mass and color saturation in trade. Yet versus the XA-30.8, the XA25 did reach a bit deeper into the bubbling cauldron of fire flies and metallic glitter as those scintillating refractions which come off strings played hot. On these Khoury tracks I also appreciated how the previously mentioned enhanced contrast tied directly to the XA25's slightly quicker percussive transients and somewhat more open overtone window. Finally and admittedly unexpected, the XA25's bass was a bit more emphatic and potent. These small but significant gains didn't come about at the apparent expense of anything else. At least on these speakers, the smaller amp began to make a most reasonable appeal to downsize yet get ahead. Time for the king of instruments, some piano.