dmmartindale@watcgl.UUCP (Dave Martindale) (04/24/84)
Is there any reasonable way to check/set antiskating on a tonearm,
other than playing a test record with signals of successively higher
cutting levels until mistracking occurs?
I KNOW the antiskate calibration scale on my arm is incorrect for my
cartridge. Doesn't the required antiskate force vary from one cartridge
(and stylus) to the next anyway?
Dave Martindale
{decvax,ihnp4,allegra,clyde}!watmath!dmmartindalesjc@mordor.UUCP (04/24/84)
I've heard that using a grooveless disc to determine the optimum antiskating gives significantly different results from using a disc with heavily modulated sine waves and looking for clipping. Allegedly, having the tip of the stylus rubbing against smooth vinyl isn't the same as having the sides of the stylus bouncing around inside a groove. Myself, I wouldn't know. My Antique Research turntable never discovered antiskating, so I just set the vertical tracking force to the max that Shure recommended, and bought a CD player as soon as I could.--Steve
rcd@opus.UUCP (Dick Dunn) (04/26/84)
<> >I KNOW the antiskate calibration scale on my arm is incorrect for my >cartridge. Doesn't the required antiskate force vary from one cartridge >(and stylus) to the next anyway? Yes, somewhat - but the variation is related to the required tracking force. That's why some tonearms have an anti-skate scale calibrated the same as the tracking force, and others do the anti-skate adjustment automatically. Backing up a bit, why does it skate? (Why do I ask? Because understanding this makes it easier to figure out what to do about it.) It skates because the end of your tonearm is bent: * \ \ +-------------------------------------------o---| * = cartridge, o = pivot The record obviously "tugs" on the stylus ever-so-slightly as it moves underneath. If the tangent to the groove at the stylus went toward the pivot, the force would be directly out from the pivot and no anti-skate correction would be needed. (In fact, this is the case with so-called "linear-tracking" turntables - and they don't need anti-skate force.) Since in the case above the tangent goes wide of the pivot (below in the drawing), there's a component of the force that acts to turn the tonearm toward the center of the record. [Why, you may ask, is the damn tonearm bent, anyway? To allow a reasonably short tonearm, yet keep the stylus reasonably aligned in the groove across the record. And so you ask, why not just use a longer tonearm? Because it's heavier, more subject to resonance problems, it looks stupid, and your wife doesn't want it in the living room.] So you add a little force to counteract the inward tendency. What determines the skating force? First, tracking force - remember your physics; frictional force is proportional to how hard you sit on it. Second, cartridge compliance interacting with the type of material you play. (At this point, the problems become intractable, but you've got something to worry about and spend a lot of money for someone else to fix.) Another comment (Jeff Frey) on the same topic: >...Spring-adjusted anti-skate leads >to difference force at the inside and outside radii of the disc, >however, so no setting will really be optimum. Yes, although you can get rid most of this - you just don't let the spring stretch very much over its travel and you can easily get the variation below a few percent. -- ...Cerebus for dictator! Dick Dunn {hao,ucbvax,allegra}!nbires!rcd (303) 444-5710 x3086
tynor@uiucuxc.UUCP (04/27/84)
#R:watcgl:-246900:uiucuxc:18500026:000:552
uiucuxc!tynor Apr 27 12:22:00 1984
The Telarc Omni-disc has a band of closely modulated sine waves.
Its a fairly easy test for anti-skate (just adjust your anti-skate until
the distortion goes away...)
The rest of the disc has other useful testing tracks including
some 'real music'. Here, they present a difficult musical passage
recorded at four volume levels, the first being relatively easy to
track, the last, quite difficult.
Highly recommended.
Steve Tynor
ihnp4!uiucdcs!uiucuxc!tynor
University of Illinois Champaign-Urbanaschamberlain@wateng.UUCP (Ray Chau) (04/28/84)
A standard procedure to set up antiskating is as Dave Martindale
mentions would be to play successively higher record signal
modulations until mistracking does not occur. An algorithim
for this might be as follows:
1) Select a modulation level representative of the records
you use. (ie. Telarc records are more difficult to track
than 22 hists/side K-tel specials
2) Have the above in some sort of sinusiodal test tone form for
ease of alignment (distorted sinusoids can be percieved
with wads of cotton stuffed in your ear)
3) if distortion occurs on both channels then increase tracking force
until one of channels tracks.
4) if distortion on right channel > left channel decrease skating
until roughly equal. And vice versa for the converse situation.
repeat 3)
The aim is to track both channels equally, while at the same time
to provide minimum tracking force requirements for minimum wear.
The underground has it that cartridges sound best at around this state,
tending to go murky with to much stylus force. The sad truth is
that the 'goden ear' maintain that the above algorithim does not
produce optimum sound. So much for trackability factors.
Ray:SIDev Group