Quadraphonic records (LPs to you and me)

akg_ca

You need a proper real Quad receiver, whether is was SQ formate or the synthesized stereo-based format QS format.

This is mistaken. There’s no reason to confine yourself to a "quad receiver" to reproduce quad. You just need a proper decoder - these were available as outboard devices.

... or the synthesized stereo-based format QS format ...

QS quad was no more "synthesized" than SQ quad. It was four channels matrixed to a two-channel format.

Ok but  a proper decoder is what ...?

tatyana69

Ok but a proper decoder is what ...?

You'd need a decoder designed for the format you’re trying to decode, such as a JVC CD-4-50 for the CD-4 format. Or something like a Sansui QSD-1 for QS-encoded LPs.

Ok but a proper decoder is what ...?

@tatyana69 see the link below:

https://www.ebay.com/itm/Vintage-Sony-SQD-2070-SQ-Decoder-Tested-Works-Great/292327234714?hash=item4...

i used to have a 4 chanell setup back in the early 70's. cd-4 had the best separation. but you needed a cartridge to pick up signals up to like 40.000 hertz with a unit called a 'demodulater' i notice that today many cartridges can go up to 40,000 hertz. i don't know if any demodulaters are available today but that's how it was back then.