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The audible difference
Since most T20 users will be confronted with the question "To PSU or to SLAP", my audition would focus on A/B-ing between the two. It was conducted in the room with my diagonal setup, bi-amping two pairs of Loth-X BS-1 sourced from a Marantz SA8260 SACD player occasionally outputting digitally through the Deltec DAC.


Britten's Simple Symphony played by Trondheim Solistene [2L 50SABD] is the world's first commercially marketed high definition Blu-Ray audio disc but the hybrid SACD is stunning enough to get anyone to sit up and listen. (Okay, I haven't got a Blu-Ray player.) This is simply ensemble artistry and recording marvel in perfect harmony. The PSU presented the dynamic first movement with more presence and slightly forward soundstage, varnished with brighter sheen and sharper (in terms of focus, not ear-drum piercing sharp) textural details. The pizzicato second movement was delicate but loaded with tension, and the PSU demonstrated somewhat more immediate bite, which was a good thing. Switching over to SLAP didn't tone down the excitement at all, and the soundstage definitely had more depth and layering. Textural subtleties were intriguing, smoother and conjuring a more valve-like atmosphere. The pizzicatos were comparatively more pearl like, yet still bouncing with vitality.

Spanish composer Roque Baños' Salomé [MK2 Music 8345106042] is an exotic musical journey that traverses time and space. The composer's imagination has taken ours back to historical Roman times to roam freely through a contemporary fusion of Hebrew and Flamenco music and Near Eastern cultural and musical idioms. The wide dynamic range and transience of this recording would have undoubtedly sent the PSU well over and beyond the 3A mark when played loud. This was the moment for SLAP to claim supremacy. By supremacy, I don't mean the SLAP could play louder. It just controlled the louder better. The opening drums in "San Juan Baustita" were not just sheer brute force but had inner detail. The Flamenco stamping and clapping in the foreground was unrestrained and in good proportion relative to the yearningly passionate chanting in the far back. When the two most challenging tracks, "La rabia de Salomé" and "Los 7 velos" got congested with the PSU, the SLAP rendered them impeccably. It was particularly impressive that in the earlier track, which vividly depicted the insuppressible rage and insatiable desire of Salomé, the excitement and sensuality of the music itself was exponentially heightened through the build-up, yet the actual musical components -- i. e. the rhythmic complexity and sonic ecstasy -- were articulated with effortless ease. New layers of conflicting meters were being invariably revived by clapping, drums, guitars, tinkle-bells and more. New angles of interception were being constantly introduced through puffing and wheezing, panting and gasping, coming from all four corners of the deep and wide soundstage. Clarity reigned. Suaveness excelled. Likewise with the discretely localized instrumental placements in the densely orchestrated climax of the erotic dance of the seven veils.

At this point, a quick note on the speakers might prove useful. When listening to the Britten piece, the Klipsch Synergy F2d showed their compliments to the warm strings and produced a luscious valve bloom. When listening to the kaleidoscopic Salomé, the Loth-X BS-1 offered spotless definition and cloudless clarity. Continuing with the Loth-X, Stokowski's Symphonic Synthesis on Themes by Wagner conducted by José Serebrier [Naxos 8.570293] achieved the same degree of spontaneity without any trace of stress with SLAP. From the thunderous opening to the triumphant climax of "Entry of the Gods into Valhalla", bi-amping and bi-slapping had proven that concert hall grandeur could be made believable. A quick reference to my favorite Dared VP-20 bi-amp + Mark & Daniel Maximus-Mini showed that both system could do real bass without the need for added subwoofers.

If the idea was to push the PSU into rippling noise to prove that it's audible, then the ultimate test would have to be Carl Orff's Catulli Carmina, which I already used in my T20 review. However, the Jochum/DGG release appeared to be out of print so this time I went for the 1995 recording conducted by Franz Welser-Möst [EMI Classics 5555172]. Although personally I still think that Jochum's interpretation is hard to beat, the EMI release is easier to find. (Note: The Jochum album of Orff's complete theatrical triptych on the DGG catalog are 1950's monaural recordings. The 1970 stereo recording has been removed.) There's no doubt that the SLAP advantage was evident in every respect, from transient attacks to three-dimensional holographic verisimilitude. At this point, I changed the T20s to T20Us and found that the benefits of SLAP were just as audible if not more pronounced. Somehow with T20U + SLAP, I found the vocals more harmoniously rich and refined. Something to do with the larger caps in the USB version that I didn't notice before?


In the following days, I downsized from bi-amp to single amp, with one T20U driving a pair of Loth-X BS-1. The before-and-after effects of SLAP were even more noticeable, most evident in 3D layering and effortless fortissimo although the magnitude of orchestral opulence was inevitably compromised due to the single amp. In order to achieve the same sound pressure level, the volume knob had to be dialed up from the 11:00/12:00 position to 1 to 1:30, even 2:00 sometimes. At this point, the benefit of bi-amping became self evident. I should also clarify that in the above audition notes, I've only cited the worst scenario for PSU or the best for SLAP. In most cases with less 'aggressive' music, the difference wouldn't bother me much. I was happy with the PSUs, the reason simply being that with bi-amping and high-efficient speakers, most music under normal listening wouldn't suck the caps dry. It would be a tough call whether one should invest in a T20U plus a SLAP, or two T20Us plus two PSUs. If you know me, you know what makes my heart grow fonder.


Having said that, I knew that it was pointless to interrogate the single amp further. So I took a different direction and changed to a new course, which was to see if I could find some CDs that would make no difference whatsoever between PSU or SLAP. I was under the assumption that it wouldn't be very difficult. There had to be some peaceful music that begged to be played soft. How wrong I was. Even with the 94dB/8ohm efficient Loth-X BS-1, I failed. The closest I thought I was to success was Gil Shaham's The Fauré Album [Canary Classics CC03] and Jacqueline Schwab's Down Came an Angel [Dorian DOR-90275]. Smooth sailing at first with Fauré. I honestly couldn't hear any difference with "Sicilienne", "Berceuse", "Sérénade toscane" or "Après un rêve". But then even a mild and placid man like Fauré had his moments of eruptive passion as in the 'Schumannesque' Sonata No. 1, Op. 13 in which he declared his vow for his long-time love (who, alas, rejected him). So was the emotionally charged Andante, Op. 75.