Stereo Amplifier

Review: Quad 606 Stereo Amplifier

The design philosophy and the basic circuit are as before but this time the 'current dumping' ability has been trebled by paralleling three pairs of output transistors in each channel and providing them with a greatly enlarged power supply. How large can be judged from the weight of the amplifier which also approaches three times that of the junior model. Even so, for an amplifier which can put out over 200 Watts of music per channel when asked, the 606 is remarkably compact. This has been achieved by making virtually the whole amplifier perform as its own heat sink. The top and bottom covers are heavy alloy castings, deeply vaned to increase the radiating area and finished in dark char coal grey Nextel paint. Internally these covers bolt to a pair of 5mm thick U-section castings on which are mounted the power transistors and the glass-fibre printed circuit boards carrying all the smaller components. Between them sits the massive power transformer and, bridged over it, a steel platform holding the two pairs of 6,800 microfarad reservoir capacitors and rectifiers providing each amplifier with positive and negative 55-Volt supplies fed from separate windings on the transformer.

The wrap-around centre section of the 606 is finished in a lighter grey metallic paint with the QUAD 606 logo in a somewhat darker shade, less prominent than it appears in the photograph. There is a small green LED recessed near the top left hand corner which illuminates when the amplifier is operational. A deeply recessed panel at the rear carries all the connections and the thermal cutout, all identical with those on the 306 but, in this case, the now obligatory On/Off switch is also at the rear. Incidentally the deep recess makes changing the main fuse rather more of a tricky job.

Summarizing in the more practical terms of reproducing music, this amplifier approximates to 150 Watts per-channel into 8 Ohm loads and over 200 Walls into 4 Ohms. This adds up to a lot of energy, easily capable of inflicting serious damage to many loudspeakers in a fleeting careless moment and no-one should buy it under the impression that, because it is Quad 's most expensive model, it must be the best. My careful listening tests have been unable to detect that this amplifier does anything to change the character of the signal fed to it-unlike a few others, praised in some quarters, which warm up the bass by allowing damping to fall off at low frequencies and soften the treble in some loudspeaker crossover areas where impedances drop. None of this for Quad. In quality of sound, the Quad 606 exactly mimics the 306 and the professional 520 (which simple statement puts it on equal terms with the best sounding amplifiers in the world) and so, if you don't really need its prodigious power, save your money by settling for the less expensive model.

If, on the other hand, you have suitable loudspeakers and like to listen loud, you will still be able to save, for at £449 the 606 can see off quite a number of rivals costing thousands. In a nutshell, economic, elegant, truly excellent and - British. We shall see and hear a lot of the 606 in the coming years.