Quadraphonic records (LPs to you and me)

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.

i bought my first system during the 4 chanell era. i bought a marantz 4300. back then you had 'sq' c-d 4 and qs. 'sq and qs' did'nt need a special cartridge. but c-d 4 did. 'c-d 4 needed a stylus that would reach up to 40,000 hertz. that's when the audio technica came out with their 'shibata 'stylus. it was an 'at15 or an at20. i beleive the 15 cost 100 dollars and the 20 was 150 dollars. i bought the 15. 'sq a needed a decoder with full logic, front to rear to have the best separation. i'm not sure about 'qs'. when i had my system i bought an album that would start with testing your c-d system. it had a tone that would signal the 4 chanells as a test to hear if your 4 chanells were working. one thing i remember is that the more plays you had on a c-4 album. the noise would increase.

also, i forgot to mention that c-d 4 needed a demodulater for the c-4 records. the 'sq' needed a decoder that would be installed on the bottom of my marantx receiver. i'm not sure wheather the 'qs'. form needed anything.