Hi-End, Hi-Fi, Home Cinema



Quad 303

The outstanding performance of the Quad 303 is largely due to the unique output circuit developed by Quad. The circuit employs symmetrical triples, greatly reducing distortion and rendering the quiescent current independent of output transistor temperature. This development enables the designers to reduce distortion to any desired degree without sacrificing stability, and to maintain this excellence under all dynamic conditions. To put this in perspective, the lowest theoretical distortion present on the very best tape and disc will still be some hundred times greater than that of the 303. Such a level is, of course, completely inaudible no matter how refined the test. The use of triples permits simple and effective control of the output current and since the voltage is also controlled, the output transistors are completely protected and must always operate within their ratings with the obvious advantages of greatly improved reliability under all conditions, without the use of elaborate and expensive circuitry. The amplifier cannot be upset even when overdriven by an asymmetrical signal or by shorting or disconnecting the loudspeakers.

Quad 303

Quad 303

Power Amplifier


Power Output:

The amplifier is intended for use with loudspeakers of 4-16 ohms nominal Impedance.

Power output and distortion for various frequencies. Continuous sine wave into 8 ohms resistive load.

100Hz any level up to 45 watts <0.03% Dtot

1 kHz any level up to 45 watts <0.03% Dtot

10kHz any level up to 45 watts <0.1% Dtot


Output Internal Impedance: 0.3 ohms in series with 2000µF and 6µH

Frequency Response: Ref. 1kHz. -1dB at 30Hz and 35kHz into 8 ohms

Signal Input Level: 0.5V rms ±0.5dB for 45 watts into 8 ohms. Amplifier loads the input by 22k ohms in parallel with 60pF

Signal Input Overload: Instantaneous recovery up to +20dB overload

Crosstalk (input loaded by 1k ohms): 30Hz-10kHz >60dB


Hum and Noise (input loaded by 1k ohms):

'A' weighted - 100dB ref full power

Unweighted (15.7kHz measurement bandwidth) - 95dB ref full power



This amplifier is suitable for use under the most arduous music conditions with speakers of impedances between 4 and 25 ohms, and for high level sine wave duty with loads of 8 ohms or greater


Stability: Unconditionally stable with any load

Power Input: 100-125 or 200-250V, 50-60Hz, 40-200 watts depending on signal level


Width: 120mm

Height: 159mm

Depth: 423mm (plus 38mm for connectors)

Weight 8.2kg

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