EXPIRED For Sale Quad Classic Integrated Integrated Amplifier (Valve)

Further Information

Xmas Special Price

Recently purchased as a floor stock Demo unit.

Lovely sounding KT66 Integrated Tube Amp.

25 watts of Class A goodness.

Not recommended for loads that dip below 4 ohms.

I spent over a thousand dollars replacing the original tubes with:

Shuguang 12ax7-T's.

6922's to NOS Siemens E88CC's

EH Gold Lion KT66's.

Will be suppied with original tubes as well.

The output section is configured as autobias so no mucking around biasing tubes.

From Stereophile review:

The new integrated is, essentially, a pair of Quad II amplifiers (ca 1953) powered with silicon rather than glass rectification and bundled with a perfectionist-quality control unit and a solid-state phono section. According to de Paravicini, the output section runs in pure class-A and is modeled after Walker's Acoustical circuit, in which a portion of the output transformer's primary winding is coupled to the cathodes of the KT66 output pentode tubes (as opposed to their screen grids, as in Ultralinear output circuits). Those transformers, of course, are designed by de Paravicini, and made in England to his very exacting specifications. The amp's output section is configured as autobias, and a bit of global feedback is used—although a less-than-typical amount is required, given that the Acoustical circuit itself provides local feedback, with apparently little loss of gain and power.

The small-signal tubes in the Quad II Classic—four 12AX7 dual-triodes and two 6922 dual-triodes—function as the phase splitter/driver stage for the voltage-hungry output section; the Quad's line stage is passive. The phono section is described as "a simple and elegant circuit with five transistors per channel." It's powered by a 36V drop from the rail voltage, and uses a combination of active and passive filters to achieve RIAA equalization. Gain is 42dB in moving-magnet mode, and 62dB when switched to moving-coil mode.

The Quad's innards are built on four PC boards: one for the input-switching relays, one each for the two pairs of output tubes, and one main board for the small-signal tubes and various power-supply components. (I never did locate a silicon full-wave rectifier, although I found a small diode bridge tucked away at the front edge of the main board.) The parts quality appeared to be fine—the output transformers were lovely to behold—and the build quality was excellent.

The casework and controls of the Quad II Classic are clearly influenced by the classic Quad 22 control preamplifier (ca 1959): The faceplate is shaped is the same manner, with a similarly big, beautiful volume control. The new Quad's source selector is a four-stop slider in a crescent-shaped slot with an old-style needle indicator above. From the outside, it gives that end of the Quad's faceplate a somewhat enigmatic smile. Not 

Given that Quad's founder, the late Peter J. Walker, wasn't around to design the Quad II Classic Integrated, the English firm relied instead on Tim de Paravicini, whose credits include the comparatively recent Quad II-eighty mono amplifiers and QC-twentyfour preamplifier (not to mention his own line of E.A.R./Yoshino electronics and countless other well-regarded products). It's with respect for both men that I say: In turning to Tim de Paravicini, Quad has probably chosen the closest approach to the original.

Installation and setup
Unlike the Leben CS300 and Luxman SQ-38u integrated amps, which I also review in this issue, the Quad II Classic Integrated is physically deeper than it is wide; nevertheless, it fit well on the top shelf of my Box Furniture D3S rack, with all four feet making full contact with the wood surface (a requirement for optimal performance, I think, but that's a topic for another day). The full-function Quad replaced both my Shindo Masseto preamp and Shindo Corton-Charlemagne monoblocks, with no need for an external phono preamp. Per my usual practice, I fed the Quad's MM inputs with signals from my Auditorium 23 SPU Standard and Silvercore One-to-Ten phono transformers, rather than use just the Quad's switchable MC input with MC pickups—but the results weren't always what I expected. Whereas I tend to prefer loading and stepping-up a cartridge with a transformer rather than an active stage, the Quad's solid-state phono preamp seemed to narrow the gap between those two approaches, differences between which were subtle.

Again, my line-level sources were an Apple iMac equipped with Decibel playback software and a Wavelength Proton USB

Listening
The first things that struck me about the Quad's sound were its up-front presentation—this wasn't at all a laid-back performance—and its readily apparent sense of drive with up-tempo music. The musical timing of all recordings was well preserved, although the Quad II Classic sounded especially fleet of foot with quick, snappy acoustic music such as David Grisman's "E.M.D.," from the first, eponymous album by the David Grisman Quintet (LP, Kaleidoscope F-5).

With line and phono sources alike, the Quad's midrange was lush and warm, with decent contrast between timbrally light and dark sounds in the mix, albeit less natural texture than I expected. In my system, driving the Audio Note cone-and-dome speakers, the Quad's most notable shortcoming was a lack of extension at the frequency extremes—especially the bottom end. Through the Quad II Classic, the dB's' "Happenstance," from their Repercussion (LP, Albion ALLP 400032J), sounded overly midrangey: the inverse of the rightly maligned hi-fi "scoop." There was fine punch and presence in the electric guitars, and the drumming sounded acceptably forceful, but the electric bass lacked that last bit of extension and power, and the Quad's slight lack of top-end sparkle conspired to make the voices sound a bit dull and lacking in presence.

Chamber music and very well-recorded symphonic fare were better served by the Quad's timbral balance. Of the former, the II Classic did a splendid job with the richly recorded sonorities of the Affetti Musicali's recording of Biber's Mysteriensonaten (CD, Winter & Winter 910 029-2). It missed a lot of the natural texture in that recording, but the Quad did allow the music to unfold with near-hypnotic intensity. As to the latter, recordist René Laflamme's masterful recording of Hindemith's Escale Romantique, performed by Daniel Myssyk and the Ensemble Instrumental (ripped from the Fidelio sampler Escales, no catalog number, www.fidelioaudio.com), was clear and spacious through the Quad amp, yet engagingly rich and warm.

Note the Quad ii Classics do not come with a remote control which for me wasn't a problem as I'm only a couple of meters away from my hifi rack.

Receipt provided for Quad & tubes.

Thanks for looking.