Quadraphonic L P played with a 2 chan. cart.


This may sound like a stupid question since I grew up in the 70's when quadraphonic recordings and equipmnet were around, but as I am getting older my memory is really begining to suck. Anyway, I am interested in purchasing a Japanese quadraphonic recording of rare LP and I can not remember if the cartridges were 4 channel or not. Thus; can a stereo cartridge process the information on the LP at least the front two channels?
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Yes.
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One kind of quad LP (SQ encoded) is simply a matrix system where the 2-channel signals are processed to derive four signals. No problem for the cartridge. It will probably sound OK.
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Another kind of quad LP (which I never tried) requires a cartridge with HF response up to at least 40 KHz, because the signal that separates out the rear channels is carried by FM modulation of a carrier in the range of 20 to 40 KHz. (Note that the cartridge does not need to have flat or low distortion in this upper range because the modulation is FM). If you play such a record with a cartridge lacking HF response you might damage the grooves. However, the good news is that because of this quad system the HF response of phono cartridges made a great improvement, and most if not all cartridges sold today would work fine. The quad system died, but we still benefit from it.
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This thread brings to mind one of the first foray's into stereo I remember. It was a tonearm that became 2 arms at the cartridge end. You put in 2 monophonic cartridges and it used special records - one channel on the 1st half of the LP, and the other channel on the other 1/2. The arm tracked both channels at the same time. It looked like a snake with 2 heads. I believe the arm and the records were manufactured by Cook.
I still use a Lafayette SQ quadrafonic decoder for the few QS records that I have. I also use it for a way to 'simulate' rear channel information for ambiance effect. There has been no damage done to the original SQ 4-ch recordings by using an 'ordinary' 2-ch phono cartridge - in my case, either the B&O MMC3 or Sumiko Bluepoint special.

Fear not, play away.

Bob P.