AV8074 - SQ Encoder
 
SQ quadraphonic encoder according to CBS SQ-system from the good old days in about 1970. I intended to use it for encoding decoded CD4 records and 4-channel tapes into SQ-signals that can be saved on an audio CD and then played back via an SQ-decoder (like Sony SQD-2020) to get quadraphonic sound.
It uses two decoder ICs Motorola MC1312P for the phase shifting as described by Kenneth Parsons.
Below are some pictures and the phase relationship for the various signal inputs. The balance control is normally not needed but can be used for testing and it also looks impressive.


 
The following measurements are made with Rohde & Schwarz UPL Audio Analyzer.

Phase difference between outputs LT and RT when signal is applied on LB input

Phase difference between outputs LT and RT when signal is applied on RB input

Phase difference between outputs LT and RT when LF = RF input

Phase difference between outputs LT and RT when LF = LB input

Phase difference between outputs LT and RT when RF=RB input

Phase difference between outputs LT and RT when LB=RB input

Phase difference between outputs LT and RT when LF=RB input

Phase difference between outputs LT and RT when LB=RF input