4 Channel surround sound, a speaker in every corner.
Towards the end of the mid 70s to the early 80s, a lot of audio companies started to develop quadraphonic sound, possibly the next thing after stereo sound. But with several companies offering different ways in which stereo was “decoded” for 4-channel set ups, no standard was reached and so it sadly disappeared from the market. Luckily, a lot of the equipment is still around and is making a comeback, often rebranded as two-channel stereo equipment. Although there are varying standards, it still sounds great.
Overview
Most common among the Pioneer quadraphonic range, are the receivers in the QX range, followed by the rarer QM and QA quadraphonic separate power and pre-amps. These were as usual built to a high standard and look and sound great with a handy second feature of being able to handle a bi-amp set of speakers if quadraphonic is not your thing. By now, most do require an extensive overhaul; remember, these have double what a standard amplifier has inside it, so there is proportionally a lot more that will get tired or fail.
Electrical
Many of these units were designed and built between 1974 to 1979 and within this period, pioneer used a number of transistors in certain models that have been known to be a “bad batch”. These can cause most of the trouble with popping, crackling dead channels etc. Sometimes when one arrives, it doesn’t even make a sound!
When a unit comes to me, I check all functions and components and modules and then undertake a complete overhaul of the electronics to ensure the unit will continue to run for many more years without the need or worry of the same parts failing again. I replace all transistors with modern equivalents which do not detract or change the units sound or tone and can help reduce the noise floor or hiss level of the unit which is always an added bonus upgrade.
The amplifier sections can sometimes blow out but again, this is all checked and there is nothing within these units that cannot be renewed or replaced. If an amplifier does blow out all necessary measures are carried out to ensure the amplifier is fully checked over and rebuilt to a high and “bomb-proof” standard where applicable. I always replace transistor pairs if one fails and gain match where necessary to ensure the best possible sound reproduction.
Many of the earlier units use what would be thought of today as a non-standard amplifier design which incorporates an “output-capacitor” in the design. This has pros and cons. One positive, is that if an amp channel does fail, the capacitor can block the dangerous voltage and your speakers remain safe and no need for a noisy protection circuit. A negative would be that the capacitors can cause some added distortion or colouration to the sound output.
These output capacitors must be changed at this age, and I only select high quality capacitors which will maintain or improve the output abilities of the amplifier, maintaining a great warm sound.
Cosmetic
Most often, the range of quadraphonic devices come from an era during which Pioneer made wooden cabinets or housings for their equipment. Most are made from plywood with veneer and this can end up looking faded from UV damage or just generally get scratched or dog eared. I can make new cases or refresh the exiting case if needed. Any grills can be resprayed if there are any rust spots present and on the occasion that there is any internal corrosion to the chassis, this can be stripped back and protected with an undercoat to help prevent the rust from progressing into a more serious problem. Sometimes, this might mean having to remove circuitry or other case hardware which would incur an additional labour cost to remove and then replace the hardware or circuitry.
If you are interested in a new case, this option is also available, either in solid wood or plywood but always finished with staining and a clear top coat to give a high glossy durable finish.