Stylus Rake Angle

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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Sorry - the article is from Practical HIFI not HIFI Answers - (from the days when there were too many hifi mags to keep track of...)

Csontos: I perhaps shouldn't have mentioned cantilevers per se, as opposed to the function of the cantilever. But have a read of the article mentioned.

John

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Atmasphere:

Take it as a definition unique to the technology that 'groove depth' means how deep the groove is with no signal.

I understand that. It is the reference point. A silent groove has a fixed depth and smooth sides.

If the cutterhead were to rise and fall with respect to the lacquer surface, then we would see a varying groove depth

Clearly that is the case.

But when the cutting stylus records any signal other than a pure mono one it must move more and less deep into the lacquer, otherwise how can the signal be cut? That was what I was getting at and confused by your answer. I didn't mean the whole mechanism moved, solely the cutter itself.

It's an interesting subject. Maybe I should get my hands on a cutting lathe...

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