Stylus Rake Angle

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.

Dear Kiddman: Great post/contribution. Thank's for that.

Regards and enjoy the music,
R.

@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).

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.

A question was posed about why the angle of the cutter and angle of the stylus need to be the same.

The trigonometry dictates that for small angles of deviation it does not matter much as the cosine is changing extremely little for angles of 1,2,3 degrees. For instance, cos 3 degrees = .9986!

Visualize this: a pointed shovel whose shape is a "V", with the "V" portion 10 inches tall. Put the shovel straight into the sand to a depth of 5 inches, and then pull it along making a "V-shaped" groove in the sand.

Now, with the shovel in the groove, lean it 3 degrees forward or back. The "V" shape of the shovel fits the V groove almost perfectly at the 3 degree angle, even though the groove was cut with the shovel vertical, or at 0 degree lean angle. It has to: the cosine of 3 degrees is .999!

But, if you lean the shovel to 15 degrees you will see that only the upper part of the groove will contact the sides of the groove, the rest of the shovel will be pulled up away from the groove. We'll only have 2 short contact points.

The shovel represents the stylus, of course, the sand the record, and the V-groove the cut groove in the record.

So, in reality, small deviations of stylus angle compared to cutter angle mean very little. Large deviations represent a increasing compromise as the difference in angles gets larger.