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How to play Quadraphonic records on a surround stereo:

Here’s a neat thing I found — if you needle drop a QS record (I did Steely Dan’s Can’t Buy a Thrill) and play it back through a Dolby ProLogic II Music decoder (there’s one built into the Oppo 970), you get pretty darn close to the original quad effect.

SQ or QS = 5.1 play back

CD4 = need decoder.


About quad records: quad records were actually always played with (technically) a stereo cartridge whether playing them in stereo or in quad. They are ‘matrix’ quad media: the rear channels’ information was electronically ‘piggybacked’ onto the front channels’ information, and the master discs for quad records were all cut using stereo cutting equipment. The two channels of information retrieved from a quad record must be passed through an appropriate decoder to extract the rear channels’ information and (more or less) reconstruct the four channels of sound.

I expect the Jefferson Airplane album is a CD-4 disc, as it’s on RCA Victor. (CD-4 was developed by JVC, Japan Victor Company.) CD-4 encoded the rear channels onto the front by mixing them with a ‘pilot’ signal, a sine wave of 22.5 kHz frequency. The proper means of playing CD-4 quad records involved using a stereo cartridge fitted with a Shibata stylus, which could accurately track this pilot signal, with less wear than other styli, and reproduce it accurately, so the decoder worked properly. In fact, the JVC Super Vinyl that Mobile Fidelity Sound Lab LPs from the 1970s and 1980s were pressed on was actually developed for the CD-4 records for its low noise and long-wearing qualities, to help reduce the tendency of the pilot signal to get obliterated from them over numerous plays.

Many of today’s higher quality cartridges and styli will play CD-4 records without damage. I can’t vouch for how well they’ll work with a CD-4 decoder, etc. The worst thing that would happen to CD-4 records back in the old days was when they got played on really crappy stereos (think many BSR changers) whose stiff styli could literally erase the pilot signal from the grooves of these records, ruining the effectiveness of them as a source of quality quad reproduction ever afterward.

The records that are marked with SQ or QS sound incredibly different, not always better to my ears, Santana’s Abraxas comes to mind, as not sounding that good at all. way to much echo, the vocals don’t seem natural either.

Some quad records I have did not have any discernible difference in sound, I did not realize at the time, I needed a decoder for the records marked CD4, as this was the only discreet quad mix, and just sound bad in the Pro-Logic setting.

The CD4 marked quad pressings sound OK using the regular stereo settings, But I would rather listen to the original through the Pro-Logic, as at least it doesn’t sound synthetic, as on the quad CD4 pressing. Also is worth noting that, some people have reported that the Pro-Logic setting only pushes the sound to the center on these SQ or QS LP’s. I have not experienced this.

Perhaps they have ears that are better trained, or possibly they have a super sensitive, or not sensitive enough receiver. The bottom line is for me: I don’t hear this push to the center at all.

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