Stylus Rake Angle


I am trying to set up my new VPI 3D arm as close to perfection as I can. On the Analog Planet, Michael Fremer gives one opinion, however, a different opinion was voiced by Harry at VPI, and Peter at Soundmith. I've been discussing this with them....Fremer says that SRA should be adjusted even if the back end of the arm is WAY high up as needed, whereas Harry, and Peter said to start with the arm in a horizontal position and move it slightly up and down to find the sweet spot. Peter said that my cartridge (Benz LPS) and some others have an additional facet in the diamond so bringing the arm up in back would be exaggerating the proper SRA. When I wrote back to Fremer, he answered with an insistance that he was correct. Does anyone want to add to the confusion??
128x128stringreen
Dear Csontos: I understand your point an opinions and I can tell you that's really tiresome to make overhang changes everytime but IMHO is necessary. Of course is up to each one of us do it or not: our each one privilege.

I really appreciated all your posts. Only under a friendly discussion we can improve our self.

regards and enjoy the music,
R.
Doug and Csontos seem to have the way of it.

The cutting stylus on an LP cutterhead only does about 10 hours before it needs to be replaced. You'd think they were all exactly the same but after replacement you wind up resetting a lot of parameters on the cutterhead. Tiny little adjustments can have a huge effect on the groove you cut, so its anything but cut and dried. I find the talk about SRA a bit amusing as a result.

As the stylus wears, sometimes you have to make little adjustments, like the stylus temperature. Funny thing- it cuts a slightly different angle depending on the temperature. Some LPs don't have very much in the way of dynamics so you can change groove depth a bit to allow for more time on the LP, conversely if something has a lot of dynamics or out of phase bass, you might cut a little deeper. So groove depth affects stylus angle too.

Bottom line: don't get too upset about it. Its more important for the mastering engineer to cut a good groove than it is to get it exactly at 92 degrees. You are never going to be too far off either- the stylus won't cut right if its a few degrees off... trust me on this one- there are far more important things to worry about :)
I don't get this "slur" thing. The stylus is rigid/ inflexible and so whether the tip or farther up encounters the groove wall first, a deflection occurs. I'm not saying none of this makes a difference but if a guy who cuts lacquers for a living and a guy who builds some of the most coveted carts in the world says move along, there is nothing to see here, then maybe we should believe them.
On the subject of stylus overhang:
If the pivot to spindle distance is set exactly right, meaning +/-0.3mm of the recommended, because that is the best anyone can do, then it seems to me that small errors in overhang (say +/-1.0mm, but I would have to do the geometry before settling on that margin) can be tolerated.
Reason: None of the accepted tonearm geometries achieve more than two points on the arc of the stylus tip where there is tangency. The various algorithms differ only in the locations of these two points along the LP surface (and they also do differ in the amounts of tracking error at other points along the way, but I am not debating that here). A small error in overhang, assuming P2S is correct, will only move those two points of tangency by small distances in or out on the radius of the LP. So long as those two points remain on the playing surface, what is lost?