Quad II-eighty Tube Amplifier Reviewed

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quad_ii_eighty.gifWhile Quad's Peter Walker is up there sparring with SME's Alastair Robertson-Aikman, arguing about how AR-A modified all of the various ESLs, there's another battle going on that might have PJW shaking his head. As far as my knowledge of Quad's founder goes, he treated power as did Rolls-Royce: adequate is always enough.

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But that hasn't stopped audio's equivalent of the arms race, and many of us savor high power as much as we show contempt for the three-watts-from-a-300B single-ended triode brigade. Clearly, the original Quad II's 15 watts or so limits its usefulness in a modern climate, mainly to users of early Quad ESLs, or - for those with no hearing above 2kHz - the most horn-loaded speaker.

Equally, the slightly beefier Quad II Classic and the first of its modern children, the II-forty with more than double the power, only just about master with the current Quad ESLs. My own experience with them has to be tempered by the fact that 1) my room is only 12 by 18 feet and 2) I am not a chronic head-banger. But bullied, cajoled and downright harassed as I have been by power brokers such as Dan D'Agostino of Krell and Antony Michaelson of Musical Fidelity, well, let's just say that I'd want 75 watts per channel, even with the most sensitive of horns.

Not that the brand-new Quad II-eighty, with a quartet of KT88s per monoblock, is going to cause Messrs. D'Agostino or Michaelson to lose any sleep. As its name tells you, the rated output is 80 watts, the '88s running, according to designer Tim de Paravicini, "As two pairs in push-pull with the hallmark tradition of partial cathode loading in the output transformer line arising the output stage, permitting lower distortion than the usual Ultra Linear or triode methods."

Suffice it to say, I am not unfamiliar with amplifiers carrying four KT88s per channel, having lived since its inception with McIntosh's sublime MC2102, which is rated at 100 watts per channel. I can tell you that the Quads hold their own, even alongside this modern classic. Politely British? Yeah, if "politely British" to you means Aston-Martin V8s and Vincent Black Shadows.

You can see by the valve complement that you're getting essentially twice the II-forty: the aforementioned quartet of KT88s, driven by two 6SL7GTs and a single 6SN7, in a substantial 177 x 230 x 422mm (WHD). It even looks like a II-forty on hormones, and I'd hazard a guess that each unit weighs twice as much, too. An IEC mains socket accepts the AC, input is single-ended-only via RCA (balanced would have been nice) and taps are provided for four- or eight-ohm speakers. Minimalism continues as per its predecessors from the 1950s.

Also likely, though, to set the heaven-bound PJW's teeth on edge, is the thoroughly modern, un-Quad-like price of £5000 per pair. This immediately places Quad in a market sector where it has only ever competed with speakers: the high-end. Instead of fellow Brits, its rivals now include all of the world's major valve amp manufacturers, brands such as Jadis, Conrad-Johnson, Air-Tight, Unison Research, LAMM, Audio Research, VTL, Manley, AudioValve and, yes, even EAR-Yoshino.
Quad sent us Tim DeParavicini's design notes, which show just how much he adhered to Walker's original concept, while manfully modernizing the design. A main difference, according to Tim, is that "Instead of two pentodes, two twin triode valves are used in 'cascode,' providing slightly more gain with lower distortion and accurate balance. DC feedback controls the 'up' pair of the cascode to ensure accurate matching of the anode voltage, as a tapped sample of the anode voltage going to the grid of that valve ensures that the cathode provides the correct voltage for the prime lower tubes, so that they run in a constant voltage mode."

Other detail changes conceived by Tim include a more robust and modern output transformer, "designed to improve high-frequency performance and accurate balance of the two push-pull halves. Also, the transformer has been designed to make sure that full output is realized at the bass frequencies down to 20Hz." Tim also stated that each output valve has its own cathode resistors to provide reliability and self-matching, while the screen grids of the KT88 valves are run from a lower voltage again for good reliability.

He restricted feedback for the whole amplifier to only 16dB, expressly to provide "good stability into virtually any loudspeaker and especially the famed Quad electrostatic loudspeakers, known to be difficult for many other valve and transistor amplifiers."

It was only natural that I feed them straight off the Quad CDP99 II CD player in variable output mode. Wires were Yter from CD to amp to speaker, the latter including Sonus faber Guarneris, which are peculiarly hungry, Quad ESL 63s and B&W Signature Diamonds. Nothing rattled this amplifier; equally, I suspect that they are overkill as far as LS3/5As are concerned.

Released when the Quad II was current, the Four Seasons' earliest hits were possessed of bass as voluminous and rich as is needed to satisfy modern tastes. With the Jersey Boys musical having rendered these recordings topical, I was delighted to find them also of reference quality for the blending of those inimitable voices, for hot, fast transients, astounding percussion as regards both mass and attack, and for cinematic stereo width. Turning up the wick ever higher, the II-eighty simply rose to each occasion, excelling with every instrument.

Thunderous though the bass is on "Walk Like a Man" and "Big Girls Don't Cry," the Quads never lost control. Those of you familiar with the difficult yet full and satisfying bass of the original Guarneri - ported enclosure, hungry crossover - can appreciate that this is quite an achievement for an amp that many would still consider to be only medium-powered. But they continued to work the lower octaves with authority and authenticity, through the Four Seasons' canon and on to the less bombastic yet equally impressive lower registers of Keb' Mo's version of "For What It's Worth."

Here the performance needed to be not just massive and controlled. It also had to exhibit a trait not often demanded of bass: a way with detail. Each note stayed its course, with convincing decay, plenty of body and proper scale. When you also consider that both the Four Seasons and the Keb' Mo' recordings are about as disparate as it gets - pure AM radio fodder, however majestic, vs. blues-based rock recorded to unplugged standards - the two are showcases of equal merit for vocals, however dissimilar. The Four Seasons based just about everything around Frankie Valli's falsetto, while Keb' Mo's voice operates a couple of octaves to the south.

Neither presented any challenges to the Quads, with vocal textures correct and present. What was truly special, though, involved the backing singers. A handful of tracks on Keb' Mo's Peace, Back By Popular Demand, feature vocal blends as impressive as the Four Seasons' trademark harmonies. Time and again, the Quads provided a shade more space around each vocalist, or good ol' separation, so that one could focus on an individual singer.

Of course, ripping recordings into their myriad parts is the antithesis of what a sublime system should do: the final result must always be a coherent whole. With the Quads, the effect was to produce something more involving by virtue of the sense of looking into the performance; at the same time, the portrayal was more realistic because of the seamlessness of the sound. 

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