The Quad Control Unit QCII


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Quad was one of the pioneering British HiFi manufacturers and the company continues to have great success today. Along with Sugden, Radford and Tannoy, Quad helped set the standard for HiFi equipment in Britain and across the world

The Quad Control Unit QC II was one of the last valve preamplifiers produced by The Acoustical Manufacturing Company Ltd of Huntingdon. Quad was an acronym for “Quality Unit Amplifier Domestic”. Subsequent products were branded Quad Electroacoustics but universally dubbed “Quad”

The QC II was introduced in 1953 and manufactured till 1959. It predates the Quad 22

When used with its partner FM and AM tuners, and a Quad power amp, the valve Quad setup represented a high point in audio design which many audio purists argue has never been bettered

The preamplifier is powered by the power amplifier (not included) and has two tuner inputs, for AM and FM tuners, plus a disc input with switchable equalisation. EQ presets include Col LP, AES, FFRR 78 and Std 78. FFRR refers to the then-new Decca Full Frequency Range Recording standard which enabled a wider range of frequencies to be recorded & reproduced. Each recording standard requires a reciprocal equaliser in the pre-amplifier to reproduce a flat response. The manual includes a table giving appropriate EQ settings for LPs and 78s from various record labels. Later record releases adhered to the RIAA curve which became the standard around 1954, but the Quad preamp allowed switchable de-emphasis for the popular standards of the day

The controls on the QC II preamplifier will be instantly familiar to anyone who’s used a Quad 33 – the later transistor preamp uses the same control layout but loses the beautiful knurled, machined aluminium knobs of the QC II. The volume control incoporates the on-off switch, there’s a switchable 5K / 7K / 10 KHz filter with a level control to cut disc noise and traditional bass & treble controls. Finally there are two white Radio / Mic input selectors and four disc equalisation switches. With both switches depressed, the tuner buttons act as a tape replay switch. The power indicator is a perspex lozenge on the bottom right of the panel marked “Acoustical”

This is a vintage amplifier from the 1950s and will need maintenance before using. It is sold as-is & untested and with only the cables & accessories shown. I have the matching Quad FM tuner in another auction (see both in the last photo)

There is a huge quantity of information about Quad amplifiers online and I’ve included links for further research in the links tab

Quad 2 Series data QC II instruction Manual QC II Data Sheet Quad - Wikipedia Radio Museum page Restoration 1956 vs 2006 - Quad versions Quad 22 info Keith Snook Quad Info