Among my engineering projects, I cut all the custom RCA test records which we manufactured for a number of clients during my years there. RCA maintained a large catalog of test records which nobody these days seems to know about. too bad I didn't "liberate" copies of more of these when we shut the plant down. They'd be useful to me now. I was also the developer of the RCA Quadulator which was the disc mastering signal encoder required to cut the only discrete 4-channel disc analog record ever manufactured, the CD-4 process. The Quadulator was about one tenth the size of the massive three-relay-rack system developed by JVC who invented the system. Toward that end, I did a LOT of disc mastering at 1/2.7 speed and 1/2 speed, both in my Indy lab and in our New York studios which were the only two CD-4 mastering locations maintained by RCA. My equipment in Indy consisted of a Neumann am32b lathe with SX-68 and SX-74 cutter heads and Neumann SA-66 (if I remember right) amp set, an old Scully lathe that I can't remember the model number of
and several older vintages of Westrex and Western Electric cutting heads and amps. But the best setup was the Ortofon DSS-731 cutter and matching GO-741 200 watt cutting amps. The 731 cutter was specifically designed by Ortofon to cut CD-4 at half speed. It had the widest frequency response of any audio disc recorder ever designed and could easily cut up to 30kHz in real time. But that performance still wasn't good enough for real time cutting of CD-4 which required response up to 45kHz with minimal phase shift between the the two channels, so we used the 731 at half speed with wonderful results. The stylus and collet assembly was very small compared with the clunkier Neumann mounts which went a long way toward providing the wonderful high frequency performance, but changing the stylus was much more of a challenge. Anyway, there's much more to relate about that experience if anyone is interested in it.
For now, I'm curious if there are any more of us old codgers on this board who have professional cutting experience from back in the 70s and 80s. Anybody out there? Anyone with experience cutting DMM in copper?
