Wow, great question!!! I didn't know I never used it, I never found a reason to spend the money when most of the best Rock at the time was in SQ, also the cost of buying another turntable and needle was a turn off for me at least at the time. When I bought my 150+ I was the breaking ground with all the Stereo experts who believed that Quad was not in the same league as their big Stereo receivers that were being offered to the public.
Basically my introduction to Hifi, when I was a kid, was my Uncle George gave me his HK Citation iV and Citation V amp and preamp when I was about 18, I used that setup till I was ruined the amp by not allowing enough space for the tubes to breath so I smoked her!. Being very spoiled with the great sound I decided to buy a Harman Kardon 930 Reciever, very very powerful 45 watts per channel with my Cerwin Vegas 3 ways with 12" woofers!
Then quad was introduced and I was a huge fan and promoter, It was lonely in those days being a quadder, I am not sure if it caused me to become anti-social to the Stereo audiophiles with their huge Marantz, Harman Kardon's, Sanusi, Pioneer flagships all nice and shiny with a million knobs and controls! I have an HK Cit 1, Cit 2 (in restoration) Cit 4 and Cit V in my audio room and they are sweet-sounding on my 4 speakers but I still prefer to listen to my music with distinguished speakers and my HK 900+ SQ circuit. Guess I am old fashioned or have grown to be stuck in my ways but hey its all about the music and I say Rock On if it makes you feel good Just Do IT!!!