QR Code Link to This Post This is a unique piece of audio history. There was a lot of excitement around quad in the early to mid-1970s, and this receiver was one reason why. The Panasonic SA-710 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.