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Quad 303 Amplifier

In 1967, QUAD introduced their Series 3 range of hi-fi equipment, the first of their transistor range, which replaced the now legendary QUAD II valve amplifier. The series 3 comprised of the QUAD 33 control unit, the QUAD 303 stereo power amplifier and the FM3 stereo tuner. According to Quad, they were not in a rush to produce this range, as they were keen to iron out problems associated with early transistor design.

The outstanding performance of the QUAD is largely due to the unique 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 QUAD 303.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. The amplifier won a Council of Industrial Design Award in 1969.

I have owned many 303's over the years and they never fail to please, a good compact size, with that great retro look and QUAD reliability. 

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