Stylus Rake Angle

Csontos,

If the cartridge manufacturers want to refer to SRA as VTA and vice-versa, so what?

They can call it what they wish, as can you, but the terms are distinct, and in adjusting every cartridge varying one varies the other.
VTA in a cartridge should be the same as the equivalent angle in a cutting lathe.
SRA should be the same as the cutting stylus angle.
My point is simply that optimising one does not automatically mean that the other is also optimised. This was the argument for using SRA rather than VTA to set up in the first place.

I used the cantilever angle as a easily understood approximation of VTA. The actual angle is that between a line drawn from the cantilever pivot point to the stylus tip and the record surface. For most cartridges this is close.

Lewm

Once the LP is cut, why should the cantilever give a damn about the cutter angle? The stylus "cares" about that in terms of SRA. So I would think that you set VTA so as to obtain proper or optimal SRA

The reason there is such a thing as VTA is that the stylus moves through an arc which is described by a radius the length of which is approximated by the cantilever and ostensibly at 20 degrees +/- 5, to the record surface. The reason for that is that the record was cut in a similar manner, the cutting stylus (while set at, say, 92 degrees to the lacquer surface), also describing an arc, as it is constrained within the cutting head. Variations in VTA cause distortions. They may be less of an issue than SRA but do exist.

But doesn't VTA become a moot point when matching SRA to whatever it is, by ear? VTA is static and fixed whether it's accurate or not. The angle of the stylus relative to the cantilever is not a fixed standard. I don't understand why you keep referring to the cantilever. If you insist that I refer to SRA as VTA, fine. It seems to be a matter of communication. Could you please explain to me the correlation between SRA and VTA?

I think what John is trying to explain is that the arc of the stylus as it moves from side to side will be slightly different if the angle of the cantilever does not match that of the cutter. Irregardless of the SRA of the stylus/cutter.

I've never seen a LP cutting lathe up close. Does the cutter have a cantilever and suspension just like a cartridge?

It's not clear that he understands the mechanical process of the cutting lathe. That could very well be a fault of mine. But what John doesn't seem to understand is that stylus/cantilever angle is not a fixed standard and cannot be used as a set up parameter by itself. As I've said, I've used cartridges with 'curved' cantilevers. My Dynavector Ruby has a 'faceted' cantilever. Cantilevers come in 'varying lengths'(think about that one for a moment). My London Decca doesn't even have a cantilever. Or at least not something resembling one as it is perfectly parallel to the surface of the record. Has anyone here seen cantilever specs being referred to for the purposes of adjustment or set up? If so , I'd sure like to see a copy of that.

I've never seen a cutting lathe either. If it does have a cantilever, then John has simply revealed an inherent design flaw in every cartridge cantilever that doesn't match either a standard length and stylus angle or that doesn't happen to match a particular cutting lathe. I personally don't think the arc of the cutting stylus is relevant just because of the motion of the medium or lacquer as it's being cut. The shape of the modulations are certainly not going to be that of a partial circle. Which affirms my position that I don't believe SRA needs to match VTA necessarily. It has to or 'may' have to match a particular 'angle', not an 'arc'.

I've found a1981 article in my "files" which explains things better than I've been able to, and uploaded it on to my blog:
Vertical Tracking Angle Explored - Keith Howard, Hifi Answers 1981

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