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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??
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csontos
1,311 posts
 
I'm still wondering why, if slant angle varies not only from record to record but by the signal itself, by a cutter who's VTA is for all intents and purposes static, does cartridge VTA/SRA need to match VMA? Does it not stand to reason that in the same way variations are produced, the same information will be retrieved? Albeit once external influences such as adverse lacquer/cutter interactions are compensated for via SRA adjustment? Once adjusted, will the play back stylus not follow the same behavior as the cutting stylus. Same VTA constant.
csontos
1,311 posts
 
When I adjust SRA to where it sounds correct, how close is it to (average?) VMA? It sure sounds like the entire frequency spectrum is correct, not just parts of it.
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rauliruegas
13,101 posts
 
Dear Kiddman: Great post/contribution. Thank's for that.

Regards and enjoy the music,
R.
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ack
115 posts
 
@peterayer: adjusting VTA/SRA affects tracking force and other parameters, so what you are hearing is probably a combination of all these parameters, and perhaps more of the tracking force than the very tiny SRA/VTA adjustment you affected (if you do the math for your 12" arm, you will probably see that the difference is less than 1/4 of a degree for a 1mm vertical movement of the arm at the pivot point - perhaps significant, but I somehow doubt it).
peterayer
1,382 posts
 
Ack, that may well be the case. As overhang changes, so does zenith along the tracing arc. I can see by how much at the null points on my MINT protractor. I lent out my VTF gauge, so when I get that back, I will see if it can measure a difference of 0.1 gram, for such a tiny VTA adjustment. Don't know if it will.

I'm hardly going to adjust all parameters for each LP. I'm going to settle on an overall good sounding average and decide how often I want to adjust VTA. I'm guessing it won't be too often, though I've found during the last few evenings, that adjusting VTA on my SME is not that difficult. There just is not a convenient scale marked on a tower like some other arms have.

I think these parameters vary less with a 12" arm than they would with a 9" arm, but then a 9" arm would have to move less than that 1mm for the same 1/4 degree SRA change. Admittedly, these are tiny changes and many will not find them worth the effort or sonic improvement to make.

I wonder if anyone has thought about designing an arm which would automatically compensate overhang and VTF for VTA changes.
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