I had an SQD 2020 a few years back ; I also sold them when new , along with other Quadraphonic kit ( not to be confused with Quad , which is the trademark of The Accoustical Mfg Co , Huntingdon ) .
Thanks to using these when new , I clearly remember what they ‘should’ sound like , and while the one I had , more than a decade ago , operated , it did not decode correctly - I put this down to ageing of the many discrete components inside , and also the possibility that previous owners may have been inside at some point .
When I bought the unit on impulse after spotting it on eBay , I had built up a reasonable home cinema system including , amongst other items : the Sony TA-E1000ESD AV preamp with Dolby Pro Logic ( I always wondered why Sony never included an SQ mode into any of their home cinema products , given the DSP capability ) ; the SDP-EP9ES AC-3 decider ; 5x TA-N55ES Power amplifiers ; IMF TLS80II loudspeakers ( Front ) ; B&W DM2A loudspeakers ( rear ) , and a home made centre speaker using the same mid/treble units as the IMFs . I had a variety of source components ranging from my Michell Gyrodec , several Revox and Ferrograph tape recorders , video sources from U-Matic , Laserdisc , Beta , VHS , Mini DV and latterly DVD ; oh and a SonyVPH 1270QM projector .
Anyway , I connected the SQD 2020 between the relevant outputs of the AC-3 decoder and the four power amps using the discrete inputs , and an additional 2ch input from the TA-E1000 to the input for decoding SQ records .
while there was output on all channels it just never was right .
I enquired at my local Sony Centre ( where I had spent many thousands ) . Their very competent engineer looked at it and said he wouldn’t attempt it , but had made enquiries and apparently Sony Japan had one specialist engineer who still worked on these and could restore and recalibrate, but it would take many months and would be expensive . I decided not to bother and eventually sold the unit on ( with full disclosure ) .
Some time later , I tired of the AV system and went back to my roots , building instead a quality 2ch music system ( as much as anything due to pressure from the lady of the house ) .
Out went the IMFs and B&Ws ; in came my Quad ESL63 Electrostatic Loudspeakers ; all the Sony electronics , including the projector went ( I don’t even have a TV now ) and in came Quad 77 pre , CD and Tuner , and the 707 Power Amplifier ( which was designed to match the ESL63s ) ; my SME Series III pickup was upgraded to a Rega RB700 arm with AT-OC9 and I got the QC power supply for the turntable . Sold three of my five Revoxes and both Ferrographs ; keeping just a std speed 1/4tr A77 and the high speed 1/2tr B77 , plus my Uher 4200 report , Nakamichi 700 and Tascam 133 ( for use with my slide projectors ) .
That has been my kit for the last decade now and I don’t miss AV . I still have a lot of video kit in my edit suite ( I work in video production ) but for relaxation I like to listen to music and still buy records regularly .
I've now come full circle ; after selling my train set when I was about 15 to fund my first hifi system , building up to a Transcriptor Hydraulic Reference turntable , Quad 33/405 amplifier and Kefkit 3 loudspeakers , before getting into AV and home cinema .
I even have model railways in the house again , thanks to my son who is into them in a big way - so everything comes back round again .
Maybe one day I’ll add a decoder / amp plus rear speakers to my existing system , but nothing will really match the ESLs .