Stereo Amplifier

Review: Audiolab 8000P Stereo Amplifier

The 8000P stereo power amplifier which is really two amplifiers in one case, for the only other common item is the massive toroidal mains transformer which occupies the central area. This has a single voltage primary, for 240 Volt supplies in the UK, and two secondaries, one for each channel. Each feeds a rectifier bridge and a pair of high quality 10,000 microfarad electrolytic capacitors to give equal plus and minus supplies. These are mounted, together with loudspeaker output relays and a comprehensive protection circuit, on a central high quality glass fibre printed circuit board immediately behind the toroid. The amplifier circuits are quite elaborate, using some 30 discrete transistors each and are also constructed on glass fibre boards. They are skillfully laid out and the standards of manufacture and quality of components are of the highest. Parallel pairs of complementary output transistors a t the rear of these boards are bolted to wings projecting from large area internal heat sinks. Ventilation slots in the base and cover are situated so as to duct air through these and as a result this amplifier stays relatively cool even after a period of heavy driving. The metal-work and its paint finish are of an equally high standard and, although the appearance is low key to the point of modesty, this is a British design which will withstand comparison with the world's finest. Happily it sounded good too.

Loudspeaker connections are via terminals with integral 4mm sockets, and power via a three-pin IEC connector incorporating a user replaceable 3.15 amp slow-blow fuse. The left and right input phono sockets are 200mm apart which is something of a problem with some manufactured twin leads (none came with either the pre- or power amplifier s although two-metre, three-core mains leads with moulded IEC sockets were provided). An unusual feature is the provision of a paralleled socket for each input to permit the addition of a load resistor if the normal 50k Ohm is too high in some applications. Connected up to the lab 8 Ohm dummy loudspeaker loads and subjected to the usual tests, it was soon obvious that the performance of the 8000P as quoted in the specification was too modest. With the mains supply standing at 240 Volts exactly and both channels driven at 1kHz, clipping occurred at a fraction below 150 Watts. Below this point, distortion measured around 0.01 % and only rose to 0.03% at 20kHz. All other parameters were met or exceeded. Substituting real loudspeakers for the dummy loads and music instead of the test tones was such an enjoyable exercise that I carried on longer than I should, using both a top-grade CD player and a professional OAT machine as sources. However, as I was later to use these same sources through the matching control unit as well, it was not time wasted. Changing back to my standard Sony Esprit power amplifiers (out of fashion some would say, but so good) produced a result so indentical as to defy identification. The 8000P is worth every penny of the near £500 it costs, particularly as it maintained its high standard driving an experimental loudspeaker which presented it with a very awkward load. The only control is a push-switch for power; there is a tiny red LED and the logo and model number appear in the discretest of type faces.