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Anti-skating question

I recently installed a new phono cartridge (DynaVector 10x4 MkII on Origin Live modified Rega RB250 on Planar 3 table). At first, I set the anti-skating force so that on a spinning grooveless record surface the tonearm would pretty much stay where it was set down or drift slowly outward. That, I assumed, was a pretty good and direct way to set the level of anti-skating force needed. Then, I put on HiFiNews&RecordReview’s test LP and used the anti-skating tracks – basically, you adjust the anti-skating until you hear no tracking distortion of the test signal in either channel. This procedure gave me a very different setting – one that does not counter (not nearly totally, anyway) the inward skating of the tonearm when set on a grooveless record surface. I would have thought the two methods would have produced more similar results. Any explanation for this? (I’ve stuck with the sonically-based setting for now.)
jayboard
arcmania's avatar
arcmania
39 posts
 
A bit off topic, but does anybody know of a website with turntable setup help/advice?
jayboard OP
301 posts
 
Arcmania, Laura Dearborn's article on turntable setup shows up several places on-line, including The TNT-Audio site has an article that describes the HFNRR test LP i mentioned earlier. It's a good record for those who don't have testing equipment. A post at Vinyl Asylum has some more links on the subject.
jayboard OP
301 posts
 
Hmm, lost some info in my previous attempt to post this..... Arcmania, Laura Dearborn's article on turntable setup shows up several places on-line, including www.gcaudio.com/Archives/ttsetup.htm ..... The TNT-Audio site has an article that describes the HFNRR test LP i mentioned earlier. http://www.tnt-audio.com/accessories/hfnrrdisc_e.html It's a good record for those who don't have testing equipment. ..... A post at Vinyl Asylum has some more links on the subject. http://www.audioasylum.com/audio/vinyl/messages/32767.html
arcmania's avatar
arcmania
39 posts
 
Thanks Jayboard, those were very helpful
bkearns
10 posts
 
You are right to set anti-skating by using modulated groves rather than blank bands on a record. The inwards force arises because a tangent to the record grooves, at the point of contact of the stylus, makes an angle of about 20 degrees to the line from the stylus to the pivot. The friction between the record surface and the stylus exerts a force on the stylus in a direction which is tangential to the record, and this is opposed by the tone-arm which pulls in a direction from stylus tip to pivot; however since these two forces are not acting in opposite directions, there is a net inwards force which is given by the following equation. Inwards Force = F * sin(theta). The angle theta, between the line from the arm pivot to the stylus and a tangent to the record groove is easy to calculate, the friction is a different matter One might expect that the friction would be less when the stylus rests on a blank band, but your observations contradict that; I also noticed the same effect with my turntable; and there was a long experiment conducted by Helge Gunderson on the Vinyl Asylum about the same question. My guess is that the stylus is carefully polished so as to reduce the friction between it and a V shaped groove, and when the stylus rests on a blank band the friction is higher, as it is the tip of the stylus which determines the friction in that case. The key point here is that many people (including the article by Laura Dearborn) recommend setting anti-skating using the wrong method, ie so that the tone-arm moves slowly outwards when resting on a blank band. Experiment shows that when anti-skating is correct it usually moves inward. Brian
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