Sansui introduced the QS quad encode/decode system in February 1972. Similar to SQ and EV-4, QS can decode any matrix-type quad encoded record along with synthesizing quad from a stereo source. Often, QS is shown on quad equipment with the designation “RM.” This stands for Regular Matrix. Supposedly, RM is the QS type without logic in the decoder.
I think Sansui’s grooviest invention was the famous Vario-Matrix circuitry. Various audio magazines described this circuitry in a most confusing manner. Some described Vario-Matrix as a “logic circuit” that improves channel separation. Another writer said it was specifically designed to synthesize a stereo source into a quadraphonic output. Whatever it was intended to do, it sure does sound good. Almost everything I play; FM, Compact Discs, records, whether it’s a quad or stereo version, is passed through my Vario-Matrix circuitry. Stereo sounds dull, lifeless, and boring compared to the sound of my quad receiver pumping out the tunes through its Vario-Matrix decoder.