Quadraphonic records (LPs to you and me)

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.

The demodulators are for the CD-4 LPs.

I remember all this stuff, but doubt I ever even heard a CD-4 record back in the day set up on a system to properly decode it; the SQ and QS formats had more market penetration, at least where I was in the NE in the early ’70s, but even those faded pretty quickly-
I gather there are people who like the effect of some of the matrixed (not discrete) mixes for two channel playback, never really bothered, though every once in a while an old record will come across my path where it is claimed to be ’quad mix’ (presumably SQ).
And in addition to the Shibata, CD-4 is what got us that lovely JVC vinyl compound for a while. 

@tatyana69

The Bryston very successfully codes 2 channel into 7.1.
I never play analogue into stereo

Why do you need 7.1 if you’re playin’ stereo vinyl at home ?

Proper stereo set-up reproduce holiographic 3D imaging and this is all about analog, you don’t need another speaker on the back of your chair and additional side speakers to play stereo vinyl.

If you playing 2 channel stereo via home theater 7.1 setup then i don’t know what you’re actually listening to, but definitely not what is on the record (mixed and mastered for 2 channel stereo in the studio). The sound/mastering angineer has just Left + Right monitors in front of him. 

When you decodes 2 channel to 7.1 how come it can be better than just Left + Right if the recordning was made for Stereo?