scott@ubvax.UUCP (Scott Scheiman) (08/26/85)
-- Hello, world. My first "real" posting to the net (I've been an avid reader for quite a few months now). Please bear with the length of this. At the end are some questions I'd like answers to. What this is about is a new (?) technique I developed a while back for adjusting anti-skating with traditional pivoted tonearms. I came upon the idea partly by accident and partly by analyzing just what skating is caused by, but later I realized that my technique just might be an improvement over relying on the anti-skating calibration provided by turntable manufacturers. I make this statement based on two things: 1) the amount of skating force (and therefore the anti-skating compensation needed) is a function of the amount of friction between the stylus and record, which in turn is dependent on (among other things) the shape of the stylus. My turntable's anti-skate adjustment has three scales, one for spherical, one for elliptical, and one for the newer "vertical line" type styli, but it seems to me that these scales are guesses on the manufacturer's part and that in some cases I might not be able to pick the proper scale or even that the manufacturer's guesses are "right". 2) When I checked the calibration of the vertical tracking force (controlled by a dial on the vertical tonearm pivot) against a balance, I found that the calibration of the VTF dial was off. Presumably the anti-skating dial can exhibit similar variation. My method is dynamic, and ignores any pre-set calibrations. I'm going to skip the physics lesson (it seems VERY difficult to send vector diagrams through this medium) and let you all work out yourselves whether my idea is valid or bogus. (If there is a demand, I just might try posting my analysis of skating/anti-skating!) So here it is: With a record spinning on the turntable, cue the tonearm over the record somewhere and then sight along the length of the stylus cantilever. Then alternately cue the tonearm onto the record and back up. The anti-skating is NOT adjusted correctly if you notice any apparent bending of the cantilever from straight toward you as it settles onto and leaves the record (horizontally, that is--it will, of course, be seen to "bend" vertically due to the VTF). That's all there is to it. Adjust your anti-skating until you see no horizontal bending as you cue up and down. (If it bends such that the cartridge body seems to move toward the center of the record as the tonearm settles onto the record you need more anti-skating compensation, and vice-versa.) I've used this technique for a few years now and it seems just fine. However, I once tried it on a friend's turntable and ran into a couple of problems. First, the amount of anti-skating which my method implied was necessary was beyond the range of her turntable (!). So, with the anti-skating set to its maximum, we proceeded to notice that the tonearm would be "pulled out" by the anti-skate mechanism whenever it was cued up (it couldn't be lowered to the same spot on the record). The friction of the cueing needed to keep the tonearm from going left or right was not up to this amount of anti-skating force (!!). So here are my questions: 1) I've subscribed to many of the major audio magazines for years now and I have never seen any reference to this technique. Have any of you heard of it before? 2) Does this method have validity, or have I made a mistake in my analysis somewhere? 3) Just how much difference does the precision of anti-skating compensation make, anyway? Maybe the calibration on my turntable is good enough as it is! 4) With the last two questions in mind, is this new technique good enough? It might be, for example, that the typical stylus' compliance is stiff enough that the amount of anti-skating variation needed to get a visible deflection might be much greater than the refinement I'd really need to achieve. Post answers directly to me or to the net or anywhere else you think they belong. Thanks! -- "Ribbit!" Scott Scheiman (Beam Me Up, Scotty!) Industrial Networking Inc. `/\/@\/@\/\ ..decvax!decwrl!sun!megatest!ubvax!scott 3990 Freedom Circle _\ \ - / /_ (408) 496-0969 Santa Clara, CA 95050
mjf@columbia.UUCP (Michael Foster) (08/29/85)
Talk about tweak!! There's a much easier way to adjust anti-skating. You can buy several test records that have tones recorded at high velocity on each channel separately. You adjust the antiskating so that mistracking distortion is equal (with luck, absent) in both channels.
rdp@teddy.UUCP (08/29/85)
In article <310@ubvax.UUCP> scott@ubvax.UUCP (Scott Scheiman) writes: > >What this is about is a new (?) technique I developed a while back for >adjusting anti-skating with traditional pivoted tonearms. >try posting my analysis of skating/anti-skating!) > > >>>>>>much stuff here<<<<<<< > >So here it is: With a record spinning on the turntable, cue the tonearm >over the record somewhere and then sight along the length of the >stylus cantilever. Then alternately cue the tonearm onto the record and >back up. The anti-skating is NOT adjusted correctly if you notice any >apparent bending of the cantilever from straight toward you as it >settles onto and leaves the record (horizontally, that is--it will, of >course, be seen to "bend" vertically due to the VTF). That's all there >is to it. Adjust your anti-skating until you see no horizontal bending >as you cue up and down. (If it bends such that the cartridge body seems >to move toward the center of the record as the tonearm settles onto >the record you need more anti-skating compensation, and vice-versa.) > > >>>>> an example of why id didn't work <<<<< > >So here are my questions: > >1) I've subscribed to many of the major audio magazines for years now >and I have never seen any reference to this technique. Have any of you >heard of it before? > This technique is QUITE old. I remember seeing references to it back in the 50's, when people first started thinking of these things. Many installers use this as a quick empirical check of things. >2) Does this method have validity, or have I made a mistake in my >analysis somewhere? > This method has some validity, presuming the following: 1. The cantilever is straight to begin with, and the suspension is linear (or at least symmetrical!) 2. The tone arm is not suffering from significant amount of friction. In the case where it didn't work, I suspect that this might have been a problem. 3. The whole assembly is level. The problem is, as you have alluded to, that the forces are dynamic in nature (by this I guess you mean varying). >3) Just how much difference does the precision of anti-skating >compensation make, anyway? Maybe the calibration on my turntable is >good enough as it is! > See below: >4) With the last two questions in mind, is this new technique good >enough? It might be, for example, that the typical stylus' compliance >is stiff enough that the amount of anti-skating variation needed to get >a visible deflection might be much greater than the refinement I'd >really need to achieve. > This is the real bugaboo of your technique. The skating forces, compared to vertical tracking forces are very small, on the order of a few percent. To get a visible deflection, you are playing with forces that are probably an order of magnitude to high, and you will end up masking other things that may be effecting the stylus (friction, etc). I had performed several experiments, using piezo-electric cartridges mounted in such a way that I could measure directly the skating forces. Those forces varied wildly, due to the following: 1. Stylus geometry 2. Tracking force 3. Modulation level on the record. 4. Radius at which the stylus was tracking 5. Humidity 6. Temperature (extremely non-linear!) 7. Cleanliness of the record 8. How the record had been previously cleaned 9. Tracking error 10. etc. So the method you mention can be fraught with all sorts of errors, and is I suspect, no better than the anti-skating force gauge. At best, they are all a compromise. Dick Pierce
sjc@angband.UUCP (Steve Correll) (08/30/85)
> ...alternately cue the tonearm onto the record and > back up. The anti-skating is NOT adjusted correctly if you notice any > apparent bending of the cantilever from straight toward you as it > settles onto and leaves the record (horizontally, that is--it will, of > course, be seen to "bend" vertically due to the VTF). That's all there > is to it... My curmudgeonly opinion is that the best solution to the tonearm skating problem is to buy a CD player, and the next best solution is to ignore the problem. But that doesn't really answer your question. You're wise to suspect the calibration of the antiskating dial on your tonearm. But I wonder (mind you, I don't know) whether your method is any more accurate. Most tonearms behave at least slightly like your friend's, drifting outward under the influence of the antiskating mechanism as they descend toward the record surface. Even if the antiskating is adjusted precisely, I would expect that at the instant the stylus touches the record surface, the inertia of the tonearm would cause it to continue moving sideways for a moment, deflecting the cantilever horizontally. One canonical approach is to play a stereo test record with identical high-level sinusoids recorded on both channels, watch the output on an oscilloscope, and adjust the antiskating so that both channels clip identically. But that assumes you have both such a test record and an oscilloscope; and it's still only an approximation because music isn't a sinusoid, and the stylus friction in the groove may differ. A simpler approach is to listen. If, on loud passages, you hear distortion from one one channel and not the other, readjust your antiskating accordingly; if not, worry instead about the deficit, nuclear warfare, or the declining morals of the young. -- --Steve Correll sjc@s1-b.ARPA, ...!decvax!decwrl!mordor!sjc, or ...!ucbvax!dual!mordor!sjc
mohler@drune.UUCP (MohlerDS) (08/31/85)
In response to your questions: 1) Yes, Audio Critic 1977 issue, several english audio magazines. 2) Fairly valid, you should probably check it at several points across record surface. Also it should preferably be an unmodulated groove - between tracks may be good enough. If it is non-linear I suspect the best place to have it closest to correct is the inside tracks (near label) because of the more difficult tracking there. 3) Tracking and thereby distortion and wear will be improved if anti-skate is fairly close to correct. 4) Anti-skate is at best a compromise, but I believe it is much better than just tracking heavier as some recommend. David S. Mohler AT&T - ISL @ Denver drune!mohler
mohler@drune.UUCP (MohlerDS) (08/31/85)
With test disc's, on a suitable track, you can also sum the two channels output after reversing the leads on one channel at the cartridge. It is not perfect for some of the reasons D. Pierce outlined in his posting, this method also has some weak spots, but you can audibly or visually (with a scope) set anti-skate fairly accurately. You may also learn some things about how good your cartridge is. David S. Mohler AT&T - ISL @ Denver drune!mohler