tonearm questions

I have had problems with the stylus skating in from the lean in spiral, even though, I seem to have all my adjustments properly set up...

Dave,
This is normal for any properly set up arm with high quality bearings, which your IV certainly has. Four factors combine to cause this behavior:

1. the stylus is more likely to touch down onto bare vinyl than hit the groove, so there are no sidewalls to resist lateral movement;

2. the instant the stylus contacts spinning vinyl, skating forces try to pull the arm inward

3. most LP's have an inward sloping lead-in ramp, so gravity is reinforcing the inward tendency;

4. high quality bearings present little resistance to arm movement (arms with rough, tight or sticky bearings have enough friction to mask this situation, which is why people moving to a top level arm from cheaper ones are often surprised or think they've misadjusted something).

There is no adjustment you can reasonably make to counteract this. Increasing antiskate to very high levels would prevent it, but that would be far too much antiskate for proper performance once the stylus finds the groove.

The "cure" is to cue slowly, carefully and purposefully. Don't just flip the cueing lever and walk away. Maintain control of the arm during cueing and listen for the stylus to find the groove. Once it does it's safe to release or push the cueing lever all the way down. This is especially tricky on edge-warped records BTW. Practice on flat ones first.

Doug

Good info here from Neal and Doug. I have found that some of my lp's just defy cuing without falling into the groove with a bit of a jolt.

Just me or do you guys have a few of these records as well?

ALWAYS drop the stylus into the first groove and not into the lead-in spiral -- for all the reasons Doug says. Yes it requires eyesight (glasses?) and a little practice -- but any decent engineer has cut a few seconds of silence into the first track, so you won't miss anything once you get the hang of it.

Rolloff, maybe I misunderstood. Did you add the curved horizontal damping trough? -- the one that comes standard on the SME V, or are you talking about something else? (I don't understand how it helps with VTA for instance.)

Also the SME IV comes with a damped cueing lever, so why would you need the Thorens Q up -- or is it an automatic device for convenience?

Doug,
Thanks for your reply. I have been very carefully placing the stylus onto the lead in spiral. I'll try your suggestion of placing the stylus in one of the first grooves instead.
Also, call me stupid, but I always figured that anti skating worked in the opposite direction. It seemed, that if I were a stylus, riding in a groove, centrifugal force would tend to spin me towards the outer edge of the record, so I figured anti-skating would counteract this, by exerting some inward counterbalancing force. What you're saying is that the opposite is true. Yes?
Nsgarch,
Yes, I purchased the curved horizontal damping trough. It comes with an adjuster for easily raising or lowering the VTA. That's the main reason I spent the money to get it to add to my arm. I find it does make a difference when switching between 200 gm vinyl, and the thinner discs, if I adjust. I haven't bothered much in the past, but the damping trough comes with a little adjuster wand that lets you dial in those minute changes. I haven't installed it yet, but someone (Doug?) mentioned it in another post, and, looking on the SME site confirmed that it provides that function. I'll let you know how easily it works once I install it. It just arrived yesterday.
The Thorens Q-up is an automatic lifting device for convenience, it lifts at the end of the record. I used to have one on my old Thorens table. I actually gave it away when I sold that table, figuring there'd be something more modern and stylish by now to go with my Oracle. Hated the Stylift, and that was all I could find, so I bought a Q-up at hugely inflated prices on Ebay. The Q-up fits between the arm and the platter. Then I bought the Audio Technica Safety Raiser on Ebay too, but I'll use that on my Lenco project table as the Thorens fits so well on the Oracle. I love not having to jump up, or even listen to the stylus at the end of the record riding in the lead out spiral.

Thanks agin,

Dave

Dave, excuuuuse me! I completely forgot about the height adjustment screw that's incorporated into the damping trough piece (more likely I "repressed" rather than "forgot" it because it's such a pain in the ass to use!)

If you haven't read the long thread I started on determining proper stylus rake angle (SRA, a term more descriptive of reality IMO than VTA) go here:

http://forum.audiogon.com/cgi-bin/fr.pl?eanlg&1140840022&openmine&Nsgarch&4&5&st0

As for your question about antiskating forces, it is somewhat counterintuitive isn't it!? The INWARD directed force is the result of the tonearm being either "S" shaped, or having the headshell cocked at an angle -- both designs are ways of keeping the the tonearm physically short (9 inches) while minimizing the tangential error of the cartridge alignment to the grooves. (Early tonearms were 12", 16", or even 18" long, straight, with no headshell offset.)

However this "offset" design creates a virtual "lever arm" which when pulled on by the friction of the stylus in the groove, tends to twist the arm inward.

The easiest way to visualize it is to imagine tying a string to the front of the cartridge and pulling on it. The motion of the tonearm will be in toward the center of the record.

If the tonearm post, the armwand, and the headshell were all lined up straight and you pulled on the string, nothing would happen. But with modern tonearms, if you draw an imaginary centerline thru the cartridge front to back extending it backwards, you'll see that the line misses the tonearm post by a couple of inches (to the right). The friction in the record grove multiplied by that two inch virtual lever arm creates an inward twisting force (torque,) which must be counteracted by an equivalent outward twisting force (antiskating force) in the opposite direction. Now, isn't that just as clear as mud !? ;--)
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