Quad 606 Power Amplifier

Peter Walker founded the Acoustical Manufacturing Co. in 1936, and since then all Quad products have displayed originality in design. Here we have a 606 power amplifier that is in reasonable cosmetic condition for its age with just a couple of minor blemishes – please see photographs. It will be suitably packaged and comes with our standard 3 month warranty.
Quad Say….
The Quad 606 is a high quality stereo power amplifier primarily intended for use in very high quality sound reproducing systems. It will normally be used in conjunction with a Quad control unit though other signal sources can be used.
The 606 uses a current dumping output circuit, a Quad Invention which eliminates many of the problems associated with transistor amplifiers and is covered by patents in several countries. In a current dumping amplifier, there is in effect both a low power very high quality amplifier and a high power heavy duty amplifier. The low power amplifier controls the loudspeakers at all times calling on the high power amplifier to provide most of the muscle. The low power amplifier is so arranged that it carries an error signal that provided the larger power transistors (the current dumpers) get within the target area of the required output current It will fill in the remainder accurately and completely. The reproduced quality is solely dependent on the small amplifier which because of its low power can be made very good indeed.
Problems of crossover distortion, quiescent current adjustment. thermal tracking and transistor matching all disappear. There are no internal adjustments or alignments, and the choice of power transistor types is less restrictive.
The performance of the Quad 606 amplifier is as accurate as it is possible to achieve by careful design, selection of components and rigorous test procedures.
Specifications:
Power output: 140 watts per channel into 8 Ω (stereo)
Frequency response: 20 Hz to 20 kHz
Total harmonic distortion: 0.03%
Input sensitivity: 0.5 V
Signal to noise ratio: 105 dB
Speaker load impedance: 4 Ω (minimum)
Dimensions: 321 (W) x 238 (D) x 140 (H) mm
Weight: 12 kg