Even 30 years after four-channel quadrophonic gear disappeared from the consumer electronics stores, it still has a handful of die-hard followers. There are several websites devoted to all things quad, and four-channel equipment regularly appears on eBay. This month's find however - a Panasonic SA 710 quad receiver - was found in a thrift store, still in working condition.
Among knowledgeable collectors, Sansui quad receivers are among the most sought-after four channel devices. It’s easy to forget that back in the day the hi-fi market was flooded with quad gear at every price point. Lafayette Electronics and Radio Shack were big players at the lower end, and there were many mid-level offerings from companies like Panasonic.
A Real 'Display' of 'New' Technology - by 1970 standards at least
The Panasonic SA 710 dates back to 1970, and one of the coolest things about it is the display. At this time, 7-segment digital displays were not found in consumer gear, but there were often displays with incandescent lamps and light shields that moved when switches were selected, which changed the display. Some were functional, but most were for show. Changing the mode switch on the 710 from stereo to discrete or matrix causes the display to switch from a green two-channel indication to a red four channel indication.
The 'new' technology in this receiver was the power amp integrated circuits. Previously, ICs had only been available for the preamp and line driver stages of receivers. Power amp ICs came out in the early ‘70s and were available in power levels up to about 30 watts. They featured an inexpensive, simplified circuit design, and took up far less real estate on circuit boards than amps with discrete components. Nowadays, it can be difficult for restorers to locate replacements for some of these devices. The 710 has four power amps in a neat row, all ending in a power amp IC. Fortunately, all of them are working.
The receiver needs minor cosmetic work to repair a broken shaft on one of the speaker volume knobs. A quick fix with brass tubing and a drill press should have things back in order.
Discrete and Matrix Quad Technology
Quad media came in two flavors: discrete and matrix. Discrete reproduction is the only true Quadraphonic system. In discrete formats, the original four channels are passed unaltered through a four-channel transmission system, presented to a four-channel reproduction system and finally passed on to four speakers. This is known as a 4–4–4 system.
With Matrix, on the other hand, the four channels are encoded down to two channels. These are then passed through a two-channel transmission medium (usually an LP record) before being decoded back to four channels and passed on to four speakers.
This receiver could accept four discrete channels for phono (there were stereo phono inputs too) as well as quad tape inputs and outputs. As of 1970, a standard for FM quad had not been developed, but the tuner had an MPX output, which presumably could be connected to an FM quad decoder box.
The 710 also had a connector on the back for a four-channel balancer. Often used with this receiver was the Panasonic RD-9775. It was basically a joystick that allowed users to virtually position themselves anywhere within the four-channel environment.
There was a lot of excitement around quad in the early to mid-1970s, but it slowly faded away. Media critics cite several reasons for the lack of success. The medium was never promoted effectively to consumers; manufacturers tended to promote their own systems to the detriment of competitors and the quad industry as a whole; confusion surrounded the competing standards for four-channel records. As for FM quad broadcasts, the battle between the front runners, Sansui and CBS, went on for several years. By the time the FCC picked a standard, interest in all things four-channel had waned.