RADAR is a price search engine. We link to the original listing — we never sell direct. Transactions happen on the source site.
Quad 303 power amplifier in good working order, early serial number. Clean overall with only minor marks.The Quad 303 is a solid-state stereo power amplifier made by the Acoustical Manufacturing Company in Huntingdon, England, designed to partner with the Quad 33 preamplifier.
Key specifications
Amplifier Topology: Class AB, solid-state (Triples output stage)
Frequency Response: 20 Hz – 20 kHz (±0.3 dB)
Total Harmonic Distortion (THD): <0.002% (1 kHz)
Loudspeaker Impedance Range: 4–16 ohms
Speaker Output: Gold-plated 4mm binding posts (stereo pair)
Specifications
Audio Inputs: 2
Audio Outputs: 1
Colour: Silver
Country of Origin: England
Year Manufactured: 1960s
Connectivity: 5-pin DIN input
Mains Voltage: 240V
Amplifier Topology: Class AB, solid-state (Triples output stage)
Input Types: 1x RCA (single-ended), 1x XLR (balanced)
Speaker Output: Gold-plated 4mm binding posts (stereo pair)
Loudspeaker Impedance Range: 4–16 ohms
Frequency Response: 20 Hz – 20 kHz (±0.3 dB)
Total Harmonic Distortion (THD): <0.002% (1 kHz)
Signal-to-Noise Ratio: >108 dB (A-weighted)
Input Sensitivity: 700 mV RMS (RCA), 1.5 V RMS (XLR)
Maximum Output Current: 10A
Dimensions (W × H × D): 325 × 176 × 120 mm
Weight: 8.4 kg
At US$383, this sits just above the median used price of US$336 and still well within the normal band between US$259 and US$411, so it reads as fair rather than cheap or stretched. Against the obvious alternative of a newer budget integrated amp, you’re paying for a classic power amp with real pedigree, not modern features.
The 303 is respected for its smooth, slightly warm presentation, good drive, and easy partnering with a wide range of speakers. If this one is electrically healthy and reasonably original, the appeal is the combination of vintage charm, solid reputation, and resale resilience; at this price, the main check is simply age-related service history rather than a pricing red flag.
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.
