Steve_Graham@ub.cc.umich.edu (03/13/91)
To the usually correct and lucid Bill Vermillion: Sorry, but you got this one wrong. The cutting stylus is angled INTO the cut, and the angle varies more than we'd all like, as I pointed out before. (I've read a number of the articles in the AES disk anthology which discuss such things.) But you are right in that ideally the playback angle/geometry should match the cutting.
bill@uunet.UU.NET (Bill Vermillion) (03/14/91)
In article <10163@uwm.edu> Steve_Graham@ub.cc.umich.edu writes: >To the usually correct and lucid Bill Vermillion: Sorry, but you got this >one wrong. The cutting stylus is angled INTO the cut, and the angle varies >more than we'd all like, as I pointed out before. My mind must have been out to lunch. You are so right. I went back to a couple of ref manuals and checked. When I was mentally picturing the cutting stylus I was picturing it wrong. Speaking of pictures, I couldn't find my book by Larry Bowden that he put together when he was at JVC cutting labs. Not very thick, but it is filled with lots of microscopic pictures of disk mastering. Probably more closeups of grooves and stylii than you would ever want to see. Looking at a couple of diagrams I can really see why there is so much of a problem tracking stereo LP's whereas mono LP's aren't. In stereo, since you are cutting at a 45/45 angle you get vertical as well as horizontal movement. The cutting stylus will describe an arc whose angle at any moment varies from the plane of the lacquer. In monaural cutting the stylus angle will always be at the same angle. So if the playback stylus pivot length differs from the cutting stylus length there will be only one place in the arc where the two match. Probably won't make a lot of difference, but it points out that it is virtually impossible to get an exact match. As I said in my reply questioning this, I think I mentioned that I might be overlooking something :-) :-). bill -- Bill Vermillion - UUCP: uunet!tarpit!bilver!bill : bill@bilver.UUCP