Quad 66 Preamplifier

A two-box preamp with no knobs on the box that matters. Quad put the whole control surface on a battery-powered infrared handset.

Overview

The Quad 66 is one of the stranger ideas to come out of Huntingdon. The preamplifier chassis carries no controls at all. Every function lives on a separate, battery-operated infrared control panel, and the preamp is essentially a remote-controlled switching and gain stage with a display. Quad's own service documentation is blunt about it: "No controls on preamplifier." Owners either like the clean front panel or curse the day the PP3 goes flat. The manual anticipates the second group by noting the control unit can be powered directly from the preamplifier if the battery fails.

The system is two units. The mains-powered preamplifier takes the sources. The control panel holds rotary Volume and Balance plus a dense field of press buttons: Disc, CD-Play, Radio, A-V, Aux 1, Aux 2, Tape, two Tilt buttons, two Bass Step buttons, two Filter buttons, Cancel, Stand-By, two Search buttons, Track, Pause, Stop and Store. The panel measures roughly 241 mm wide, 175 mm deep and 50 mm thick, and weighs about 0.76 kg with the battery aboard. The battery is an alkaline PP3, and Quad rated its life at approximately one year with normal operation.

Input flexibility is the quiet strength here. The preamp accepts up to seven sources - Disc, CD, Radio, A-V, Aux 1, Aux 2 and Tape with off-tape monitoring - and a second tape recorder can hang off the Aux 2 input. The A-V and Aux 1 inputs get anti-hum-loop circuitry. The Disc input is specified at 3 mV into 47 kΩ with 220 pF, and Quad's literature notes other disc-loading options were available. Line inputs sit at 100 mV/100 kΩ for CD and Radio, 300 mV/33 kΩ for A-V and Aux 1, and 300 mV/100 kΩ for Aux 2 and Tape.

The measured numbers are respectable for the period. Signal-to-noise runs 90 dB at volume maximum and 75 dB at the 300 mV reference for Disc, rising to 93-99 dB on the line inputs depending on setting, all A-weighted below 500 mV output. Distortion is quoted at a worst-case 0.05% on any input. Frequency response is ±0.2 dB from 15 Hz to 20 kHz on everything but Disc, and the RIAA stage is flat within 0.5 dB from 30 Hz to 20 kHz. Channel separation exceeds 75 dB across the band, and residual noise with the volume at minimum is a claimed −105 dB. The amplifier output is 500 mV into 940Ω with 1.5 V maximum. The tape outputs are 300 mV into 3k3Ω.

HiFi-Stereo (August 1990, p.35) reviewed the 66 preamplifier alongside the matching compact disc player, and its test report describes the control panel as a separate, essentially complete infrared remote — which is exactly the point and exactly the problem. The same review (p.36) walks through the ergonomics: the volume and balance knobs are finished in a darker metallic gray, settings are echoed on a trapezoidal display to the right of the preamp's front panel, and the volume indication is a row of indicators whose count scales with the setting, with a short line beneath marking center balance. The Stand-By button fades the volume down and shuts the system off, restoring settings when powered up again — a genuinely civilized touch, and one that reviewers singled out.

The 66 uses the Philips RC-5 system for the Quad CD player or any other player speaking that protocol, and the control panel carries a dedicated microprocessor for the job. The preamplifier's own display shows all functions selected. Mains voltage is set by links on the PCB, covering 100-120 V or 200-240 V at 50-60 Hz, with consumption around 6 VA and a 100 mA anti-surge fuse. The preamp chassis is 321 mm wide, 80 mm high and 255 mm deep plus connectors, at roughly 3.3 kg.

Servicing is straightforward by the standards of the day. Quad's service data notes the 66 contains no internal presets or adjustments, and dismantling needs only basic tools. The top cover takes four screws and only refits one way round, with the longer cut-out to the rear. The audio boards are split left and right and unplug via connectors. The main processor/display/power supply board comes out with five screws plus two into the front panel, and later issue boards add two yellow fuse wires and a black neutral wire to disconnect. Display bulbs are a replaceable item, and the parts list runs to a screened rear panel, a grey painted chassis, phono socket banks and a pair of 3 mV disc modules.

The honest caveats are the obvious ones. A preamp with no local controls is a single-point-of-failure design: lose the handset and you're reduced to whatever the front panel offers, which is nothing but a display. The PP3 is a consumable, and a decade-stored example will likely need one plus a check on the display bulbs. Collectors should also confirm which disc modules are fitted, since the 3 mV input was configurable. None of that makes the 66 a bad buy — it makes it a preamp you buy with your eyes open, ideally with the control panel present and working.

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