Stylus Rake Angle

Raul

The analog medium is full of imperfections and we have to deal with in the best way we can. Sometimes I think is an endless enterprise.

At the end each one of us have its own targets and MUSIC sound reproduction and each one trade offs choosed are related to achieve those targets.

Yes, I agree all is compromise with regard to set up, especially with regard to SRA and VTA which are decided by the cartridge manufacturer. It is up to each listener to decide what is acceptable to them, and to be aware of why it is so.

Csontos

For all intents and purposes, VTA and SRA are virtually the same thing because it is impossible to perfectly maintain standardized specs. This is why the only way to match the two is by 'listening' and at best, listening on the fly.

The issue isn't that there is or isn't a standard (if recommending anything between 15 and 25 degrees for VTA constitutes a useful standard), but that it appears that the SRA parameter is variable depending on the mechanics of record cutting, and is at best an approximation of between 91 and 95 degrees, and can vary across a record. It also varies with downforce, and with offset, which in turn depends on chosen geometry and the accuracy with which it is set.

Until someone makes a headshell which allows variation of VTA/SRA without altering overhang and downforce, then those will be factors...

More info - old articles- here

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John, What do you think is meant by the first sentence in that article you referenced?:

"Adjusting the cartridge for optimum SRA may alter the VTA away from optimum. Or vice versa."

I usually think of VTA as a useful surrogate for SRA, but I guess that a separate function of VTA, apart from its direct effect on SRA, would be to alter the angular relationships between magnets and coils, but that is a major function of VTF. The cantilever/magnets/coils are fixed in space except for the effect of VTF to re-position the cantilever, if too much or too little VTF is applied. Which takes me back to my question; what are they talking about?

There actually is a standard cutting angle. It was changed from 15 degrees in the '60's, to 20 in the '70's. I think you've reiterated the pertinent points I've already made. However my conclusion is still that the best compromise is the ability to adjust SRA on the fly. That way the manufacturers and cutting engineers can go fly a kite:)

From what I understand, the cutter head angle may be a particular value, but the resulting profile on the record is different due to the springiness of the lacquer material which varies with temperature, such that the resulting optimum SRA is not that at which the record was cut. Variations in modulation mean that the cutter has to dig more or less deep, thus varying temperature and hence the profile, so that an optimum SRA at one point on the side may not be so at another. Would that be correct?

No- but that is a common myth to which I subscribed before I started working with the cutting lathe. There really isn't 'springiness' in the lacquer surface. When modulation varies, the groove depth stays the same and the two can be set independently. The heated stylus cuts through the lacquer like butter if its set correctly - if not you get surface noise.

Csontos, I have been flying kites for some time :) seriously! But you are correct- if you can set SRA/VTA on the fly. LPs thicknesses vary as do the cutter angles. There is no other way to do it IMO. I don't think the thing you mentioned about standard cutting angles is correct though. What I have seen is that the cutter stylus needs a slight amount of rake (varies with each one as I said) and its really in the 1-4 degree range off of exactly perpendicular to the LP surface, so about 91-94 degrees. What we really don't know because no-one has really studied it is whether or not the best SRA position in playback is actually the same as the cutterhead was set to... I suspect that that varies with the individual cartridge.

I agree.