The CBS SQ Quadraphonic System

The quadraphonic SQ system was developed by the CBS Corporation, and Motorola produced the integrated circuits. The system consists of three ICs; however the MC1312P decoder matrix can be used without the other ICs, which only serve to enhance front to back separation. As you can see from the block diagram, it is an extremely sophisticated system, and the ICs drastically reduce the component count. To get an idea of the amount of circuitry packed into these ICs, I later built the decoder matrix section using discrete MOSFET transistors, and had to use 12 transistors! Although these ICs are no longer in production, there is often some old stock available on auction sites, however be careful of fakes, as those are in circulation as well.

Circuit Diagram

There is plenty of information in the documentation regarding the SQ system and its mathematics, however one thing lacking is information on how to build one. Hence, this multi-part article focuses on the three circuits and their build. If you are considering building one, then the articles on this site might prove useful and provide ideas on how to best approach this project.

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