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Quad 405 chassis, disassembled and incomplete — faceplate and PSU sub-chassis only. Spares or repairs. Everything shown is included, nothing else. Specifications
Audio Inputs: 2
Year Manufactured: 1970s
Mains Voltage: 240V
Power Output: 100 W per channel into 8 Ω
Amplifier Topology: Current-dumping (Class-A front-end + Class-B output stage) with feedforward error correction
Speaker Load Impedance: 4 Ω to 16 Ω
Input Connector: 4-pin DIN socket (stereo; DIN-to-RCA adaptor cable supplied)
Input Sensitivity: 500 mV for 100 W output
Frequency Response: –1 dB at 20 Hz (12 dB/octave subsonic filter); –0.5 dB at 20 kHz; –3 dB at 50 kHz
Damping Factor: 80
Channel Separation: 85 dB at 1 kHz
Dimensions (W × H × D): 340 mm × 115 mm × 195 mm (13.4" × 4.5" × 7.7")
Weight: 9 kg (20 lbs)
At US$56, this Quad 405 is priced way below the recent used-market center: the median is US$390, with the 25th percentile at US$333 and the 75th percentile at US$521. That makes this a strong bargain on the numbers alone, assuming the unit is functional and not missing anything major.
The 405 is well-regarded as a straightforward, muscular power amp with a long reputation for delivering clean, controlled sound and pairing well with revealing speakers. At this price, the upside is obvious: even a cosmetically ordinary example can be a very good buy if it powers up properly and hasn’t been abused. The main thing to check is basic operation and service history, since age-related maintenance matters more than cosmetics on a piece like this.
Independent perspective — not a price guarantee. Always verify condition, accessories and provenance before purchase.
Quad, the venerable British hi-fi brand, traces its origins to 1936 in London, when engineer Peter J. Walker founded S.P. Fidelity Sound Systems, soon renamed the Acoustical Manufacturing Company. Relocating to Huntingdon in 1941 after wartime bombing, the firm shifted from public address gear to domestic audio amid post-war demand for superior sound reproduction. Walker's pioneering ethos—prioritizing "the closest approach to the original sound"—defined Quad from its early QA12 amplifiers, adopted by the BBC, to the iconic Quad I of 1953.
The brand excels in amplifiers and electrostatic loudspeakers, revolutionizing both categories. The Quad II power amplifier of 1953 introduced cathode coupling for vanishingly low distortion, while the 1956 ESL 57 delivered the world's first full-range electrostatic speaker, employing a massless film diaphragm for unparalleled transparency and transient speed. Quad advanced into solid-state with the 1967 303 and transistor designs featuring innovative "Triples" output stages, later expanding to integrated amps like the 99 series, moving-coil speakers, and modern electrostatic models such as the ESL 988 and 989.
Today, under the International Audio Group since 1997, Quad holds a prestigious position in the high-end market, revered by audiophiles for its unyielding pursuit of accuracy over trends. Its heritage components command vintage collector status, yet contemporary offerings maintain a niche boutique appeal among discerning buyers seeking refined, distortion-free reproduction that honors Walker's legacy.
See all Quad listings on RADAR.
