Turntable antiskate adjustment

This is my own turntable I've just gotten out of the closet. I'd like to listen to some of my 70's records. The unit I'm working on is an old Thorens TD160 turntable with an Stanton gold body 500 cartridge. The cartridge is equipped with the elliptical stylus designed to track at between 1 and 2 grams. I'm presently tracking at

1.25 grams without any apparent problems.

I would like to set this up as accurately as possible. I'm hoping that someone can advise me on this. The manual I have is for a slightly different unit with a newer tone arm, and all it mentions about anti skate is to set it just slightly lower than your tracking weight. It seems to run fine what ever anti skate is set to and although I've made that adjustment to just over 1, I would like to be a bit more precise than that if possible.

I thought I recall (way back when) that there was a procedure whereby you leveled the unit, and then you played this "record" without grooves. If the stylus remained in one spot without drifting then your anti skate was correct. If it drifted, then a slight adjustment on the anti skate was in order. I don't have any such "record" and I can't think of a way to do something like that without damaging the stylus. I was wondering if anyone had any further information pertaining to this procedure? Thanks, Lenny

Reply to
captainvideo462009
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I think I do recall reading about that procedure. Even it is somewhat approximate, though.

If I remember correctly... the antiskating mechanism is providing a sideways force, which is intended to counteract force which attempts to cause the cartridge to skate inwards. This compensation helps the stylus track the groove with equal pressure on both groove walls, so that neither channel will start mis-tracking (stylus bounces away from the groove wall) prematurely during loud passages.

The inwards force appears as a result of friction between the stylus and the groove. This friction generates a force which is along the axis of the cartridge (perpendicular to the contact line between the stylus and the groove), and because the cartridge is mounted at an offset angle (its axis does not point straight back at the tonearm pivot) part of the friction force acts to pull the cartridge inwards.

The actual amount of skating force generated, depends on the amount of friction "pull" between the stylus and the groove. This, then, depends on the stylus tracking force (downwards pressure), the shape of the stylus and thus its contact area with the groove (conical, elliptical, line-contact), the speed with which the vinyl is passing under the stylus (faster at the outer edge), and the amount of groove modulation (louder passages -> more friction).

So... the "correct" setting of the antiskate adjustment is always going to be a compromise. Some antiskate systems generate a constant sideways force at any given settings (e.g. those which use a simple weight-and-thread mechanism). Others may vary the actual sideways pressure as the record plays, to compensate for the vinyl-to-stylus speed variations (e.g. those which use magnets, or play interesting geometric games in their mechanical contact to the arm).

Setting the anti-skate using a "blank" vinyl disc is certainly one possibility. I don't know whether a disc of other material (e.g. a plate of glass) would have the right amount of friction. A disc without grooves would have a very different vinyl-to-stylus contact shape, though, and might generate a different amount of skating force than a real record would.

Another approach I've seen uses a specialized test record, which has highly-modulated (loud) grooves using a single sine-wave tone. You play the record at several positions (inner and outer grooves), look at the left and right channel waveforms using an oscilloscope, and adjust the antiskating force so that mis-tracking starts to occur in both channels at the same time.

Unless you really want to get into laboratory-grade fiddling around of this sort, though, I suspect that what you've been doing is probably right in practice... set the anti-skating adjustment to a value corresponding to your stylus tracking pressure, on the reasonable assumption that the turntable manufacturer calibrated the adjustment in this way (it's a very common technique).

Set it up this way, after you've set the tracking force correctly (mid-way through its recommended range, or perhaps a bit higher... using the low-end of the range is often not a good idea as it can result in premature mistracking) and you'll probably be in the "sweet spot".

Reply to
David Platt

I thought I recall (way back when) that there was a procedure whereby you leveled the unit, and then you played this "record" without grooves. If the stylus remained in one spot without drifting then your anti skate was correct. If it drifted, then a slight adjustment on the anti skate was in order.

This is a good starting point, but the antiskate won't be high enough. There is less friction when the stylus contacts a flat surface, rather than the groove walls.

Stereo Review had a test record with an overmodulated groove. The left and right channel differed by three Hz (I believe) -- 300 Hz and 303 Hz. This caused the lateral and vertical modulations to go in and out of phase three times a second. You simply adjusted the anti-skating until the distortion was the same on both channels.

That's the way I remember it, anyhow.

Reply to
William Sommerwerck

There's another way to do it, which I'd forgotten.

While the pickup is playing a modulated groove, look at the pickup from its front. When the anti-skating is correct, the pickup will be centered over the groove.

Reply to
William Sommerwerck

Good luck with the adjustments. Though I can't contribute anything useful to your post I can say that about the only good thing from the

70's was some of the music. For example, Swiss Movement. Though recorded in '69 I first heard Les McCann and Eddie Harris in the early 70's. Compared To What, Cold Duck Time, and without Les McCann Listen Here.There was good music from Pink Floyd too. Oh, and Jeff Beck's album Blow By Blow. I especially like the cuts She's A Woman, You Know What I Mean, and Freeway Jam. I always play Freeway Jam when I start out on a long road trip. I recently played She's A Woman for my 34 year old son. Just because it was next in the queue when I wanted him to listen to the sound system in my car. He remarked after it was over "Who was that? Is it new? That was great! Excellent guitar work!". He was surprised it was older than him. Eric
Reply to
etpm

More correctly, it will be at the same place it is when the needle is held up in the air (not all styli -- especially old ones -- will be perfectly centered).

Isaac

Reply to
isw

I saw Britt Floyd in Boston last Spring. If you've never seen them you should. They were incredible. The Wall, they made Pink Floyd sound like the tribute band. Lenny

Reply to
captainvideo462009

aying a modulated groove, look at the pickup from its front. When the anti- skating is correct, the pickup will be centered over the groove.

THAT is the really right way usually. I lik the distortion method but there should be no distortion, at least visible.

Personally, if I own the LPs I track it very high. Very high, but it is onl y for transcription purposes. I play it once. Well I might have to do once to get the level right. I havd a 0.002 X 0.007 hyperelyptical I tracked at about twoo and a half for thisd purpose.

Sue me. I wanted i once, for this time only and recorded it in the highest format the PC would do, and then burnt it to disk. Want to hear it ? I cvan arrainge that. it is a Cristmas album. From about 1968, it has close to th e best quality sound i have ever heard on an LP to this day, and that inclu des half speed masters and shit.

I used an Audio Technica At 13Ea for this on a relatively cheap turntable, a Marantx 6120. I lost my Dual in the fire and never replaced it. Anyuway, I cranked the tracking force, I want this clean THIS ONE TIME.

Give it trackng force until it cannot take anymore, and then adjust the ant iskate to where the stylus is in the middle. You MIGHT have to adjust this for different tracks on the LP.

Another thing is to realize the actual angle the cartridge must be placed. It is not always what the manufacuturer says. A Thorens probably will set u p right using the factory instructions, but then is it what YOU want ?

if you are going to use this for transcription, you could concievably adjus t the antiskate for each track.

the oproblem here is the lack of REALLY good linear tracking turntabtles. T he record were CUT with a linear tracker, what stands to reason here ? The problem is that by the time they started builing them, much of the quality i s gone. If you got a couple of grand for the really good stuff you can ge t like thatl you would not be asking about this.

For transcription, I know this sounds so hillbilly, but stick a dime on it and two VHS tapes on the left side to prop it up.

In fact, I forgot that I had already put up the file, here it is :

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I think it sounds pretty damn good.

Reply to
jurb6006

Yeah I know, got a buzz on, can't see wortyh a shit and......

Reply to
jurb6006

This won't be much help to you with your particular problem of the moment, but if you want accurate reproduction, parallel tracking is the right way to do it.

With a radial arm, the spurious side forces due to friction are the least of your worries. There is a constant variation between the angle of the cartridge and the angle at which the groove was cut. In stereo this results in time displacement of the two channels and in mono it results in comb-filtering at high frequencies.

I didn't believe there was much improvement to be gained by using parallel tracking until I was persuaded to try it - the results were worth all the time invested. Fiddling about trying to optimise the geometry of a radial arm is just 'polishing a turd' by comparison.

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Reply to
Adrian Tuddenham

moment,..."

This is S.E.R. which means out of fifty responses about two of them hit the spot. How many S.E.>rers does it take to answer a question ? The number ha s never been determined.

You are absolutely right about the linear tracking, though realize it is no t perfect either. Nothing is friction free enough so therefore there is a m otor and an optical pickup that tells the little motor when to turn. It jog s along as the record plays which thus means there is tracking error oscill ating between negative and positive angle to the groove. It is still a hell of alot better.

Among the worse of ideas was the aesthetically attractive yet a practical n ightmare known as the S shaped arm. First of all the thing has more mass. T he best arm is a straight line because it will have the lowest mass. Anothe r thing about those Ttables is that most of them set the cartridge wrong an yway.

They generally tried to set the geometry so that tracking was perfect at tw o point of the radius. they made a mistake thogh because they set the secon d point too far from the innermost grooves. That is where it is the most cr itical. That is where this non-tangental angle HURTS the most and causes th e worst groove wear.

I had a couple with the S shaped arm and once I set it up as I saw fit, it looked like the cartridge was in cockeyed, but the thing played well. I mea n really well. I didn't get that muddy sound toward the end of a side.

I played ALOT of vinyl in the day. Funny now I would only consider it for t ranscribing to digital.

One of my favorite Ttables ws the Dual 1229. First of all you could set the thing right on top of a speaker and it wouldn't get much feedback. Secondl y, not only did the thing not have to be level, it would play standing up o n its side. I shit you not. the arm is balaced in all axes and the tracking force and antiskate were applied by calibrated springs. If you are going t o have a conventional arm, that's the way to do it.

And of course make it as long as possible.

Reply to
jurb6006

Lenny,

That is a very nice turntable but not a very good cartridge. I would track it at at least 2 grams. Chuck

Reply to
chuck

The un-servoed parallel tracker was of dubious value, even in the days of coarse-grooved 78s.

If the servo is correctly designed, the error can be very small indeed - probably smaller than the error in the original cutting facet.

The trick is to have a high loop gain with a very long time constant, lurking in the background of an ordinary much faster loop with less gain. Velocity-proportional feedback is also needed for damping the loop. Finally, there needs to be an over-ride system which disables the time constants and puts the motor on full power when the error exceeds a certain range. Otherwise, when the user lifts the pickup to return it to its stand, he will have to wait all day for the servo to catch up.

Not every disc was cut with a correctly-aligned cutter, so it is helpful to have the cartridge on a swivel mounting if you intend doing archive work; an X-Y scope on the two channels is the most accurate way of aligning it.

Also, there could be worse torsional resonances in an 'S'-shaped arm than in a straight arm of similar construction.

If the arm is radial, that makes sense because it minimises the angular changes; but there are advantages to a short arm, which can be exploited if a parallel tracker is used with the carriage track running partly above the turntable.

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Reply to
Adrian Tuddenham

That's not a good setup for discs that are warped or had an eccentric hole -- and there were a lot of those. Arm mass should be low to deal with those problems.

Isaac

Reply to
isw

Trevor Wilson forklarede:

You might want to rephrase the last statement :-)

Leif

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Reply to
Leif Neland

An S-shaped arm is theoretically inferior to a straight arm, if only because it's less rigid. It does, however, accrue several advantages from the ability to easily design a removable head shell.

Reply to
William Sommerwerck

It's the effective rotational inertia of the mass which is critical, not the actual mass. An arm could be massive at the pivot and slender at the cartridge end whilst still retaining a reasonably low rotational inertia.

Other problems arisewhen attempting to play very badly warped discs, such as the disc hitting the underside of the arm. If the arm is designed to be well above the cartridge, so as to avoid contact with the disc, then the displacement of the cartridge mass from the centre of torsion of the arm can worsen the rotational resonances in the arm.

The whole business is fraught with difficulty

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Reply to
Adrian Tuddenham

That about sums it up. Thing is, remember at one time that's all we had. Th ink of all that went into making this inherently imperfect system work "per fectly".

I liked it. I liked the challenge of making things sound as good as possibl e given rotating disks and moving tape across heads. I liked looking at the print of an FM tuner even and figuring out which one was best. Damn, I rem ember when there wasn't even a PLL in an FM tuner, it had a sharply tuned c ircuit to pick up the pilot frequency and then a doubler. No oscilator. (

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jurb6006

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dave

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Adrian Tuddenham

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