Anti skate question

I would bet it’s that Peter Ledermann is advising less antiskating than has been customary.

 

He supposedly is just quoting Schroders research, so if you can show evidence that its the correct way then customaries can go out the window for all I care, as long as its correct.

 

Peter didn’t show evidence. Do you have evidence that satisfies you on the topic?

 

Indeed, I dont, I just trusted his word on Schroders research, but Ive wanted to ask him about the topic for long.

 

Steve- maybe you can lend some clarity to this (and I could ask Peter too if and when I talk to him). The area "at the end of the record on the un-pressed flat space where the run-out groove is" (to quote from the above which I think is a quote from P. Ledermann) is not really blank- there is a run out 'spiral' (for lack of a better word) rather than a normal record groove with modulated information in it that drives the stylus toward the label.
Sometimes, these are cut very mildly and other times, very aggressively, in terms of curvature or in how quickly the stylus is driven toward the label.
So while I understand the concept and use it myself as one of several ways to monitor anti-skate force, to some degree the arm is still being driven by a groove in that 'flat' space-- perhaps not heavily modulated and obvious at the end of the record, but still guided by a groove in most instances. And, depending on the record, that run out groove or spiral has varying degrees of curvature, depending on the record.
How does this affect the validity of using this approach and your view on the subject?

 

It doesnt have to have any grooves at all though, as far as I understand it. You can have a totally blank record side and it could work in the same way. The only reason deadwax is suggested is because everyone has that while not everyone has a blank record.

 

I'm talking about the lead out, the gentle spiral cuts- not the modulated grooves- that appear in the deadwax- they usually lead the stylus to the lock out or label and used to trigger changer mechanisms. Still on modern records. The stylus traces those- I've had some that are tighter spirals than others. How that affects the behavior of the stylus in the run out is what I'm curious about---there's actually an RIAA spec for these but I've found them to vary in degree of curvature.

 

Yes, lead out grooves. Ive seen very varying speeds at which they lead towards the label too. But I dont see how they would affect the stylus when its only supposed to ride the blank area. If anything I think runout matrixes would have more of an affect.

 

Leon- I'm not trying to be difficult here. How does one avoid the run out grooves in observing the behavior of the stylus if using the end of the record? They are there to drive the arm to end and the stylus tracks them-- you can see the lead out from the last modulated groove to the lead out spiral and that spiral varies, depending on how the record is cut.
I thought Ledermann's premise (ala Frank Schroeder) was to avoid using a test record track which was too highly modulated to represent an good 'average' and that using a highly modulated track would tend to cause one to set anti-skate force too high.
I know there is a lot of controversy about how to best set anti-skate- I'm not trying to address all of the issues in this,* but one specific question- that is, the effect of the degree of curvature of the lead out groove on stylus behavior if you are using the Peter/Schroeder method. (As to playing matrix info- the inscribed alpha numerics or other things in the deadwax- I don't think that happens because that coded info is inscribed or stamped in the spaces between the lead out grooves- thus, the stylus never traces the matrix info, but is led around it by the lead out groove, at least as I can see based on a quick examination of several records).
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*One issue- which isn't necessarily germane to my question, is whether to use a blank disc or a modulated groove. I'm not taking a position on this here. I understand that skating behavior is affected by a variety of factors, including the degree of modulation of the groove- that is precisely Ledermann's point in avoiding highly modulated test tracks. The lack of modulation in the lead out groove is another question, which I'm also not trying to answer here.

 

I don't know if it is a valid approach, but using a mono record as a reference and following the Soundmith method I get these results:

 

Bad antiskate means the needle is pressing harder on one groove wall than the other.

The difference between correct antiskate and no antiskate is about 20% of the tracking weight. It isn't so much about groove wear, but the sound quality you lose from a stylus cantilever being pushed sideways by an invisible force, and poor surface contact.

If putting the needle on uncut vinyl was a questionable technique, this is only made worse by adjusting at the radius extreme of center dead wax, and on a turntable known to have a poor mechanism with inconsistent force.

Fun With Anti-Skate Adjustments?

 

Hey Bill,
I think Lederman suggests the lead out area just in case someone doesn't have a blank "one sided" record. The anti-skate test must be observed quickly before the stylus gets picked up by the lead out spiral. The time frame will be a brief moment to tell which way the arm "jogs" or moves before the stylus engages the lead out groove. It's kind of an awkward method to test the anti-skate, but does work.

Another problem can be the auto-return engages as the stylus is set on the lead out area.

The better blank test is with a blank LP, such as a one sided disco record.

 

This is true. Another way to look at this; the skating force is linearly proportional the the drag force. Obviously the drag force will be greater in an actual groove compared to a blank area. So the skating force will be greater in a groove compared to a blank area. So you should not set the anti-skate with a blank area.

After many years of playing records, I now fine tune the anti-skate control by ear. You can use a mono record with sibilant vocals played back in stereo. With the anti-skate set properly the hissing distortion will be centered with the vocals. If it images to the right channel, the anti-skate is too low.

 

Shure of course carried out a whole load of measurements of anti-skate, available to peruse here

https://www.americanradiohistory.com/Archive-Audio/60s/Audio-1967-10.pdf
https://www.americanradiohistory.com/Archive-Audio/60s/Audio-1967-11.pdf

Articles by James H. Kogen, called "The Skating-force phenomenon"

Also a summary here Skating Force Information

 

As @The FRiNgE suggested.

 

Thanks for these.

One thing that stood out was that an increase in surface velocity did not have an effect on the skating force. This has me rethinking my anti-skating because I find that a hotter cut 45rpm 12" requires more anti-skating. In reality, it might be that I am not using enough anti-skating force at 33rpm and don't really notice it because the recordings are not hot enough to cause audible issues.
Just this weekend I played a few 45rpm albums and bumped up the anti-skate to do so. It was audibly clear on the first side that I forgot and had to go back and adjust it. I guess I should leave it where it sounds best on the hotter cut records.

Another point from these, they compared un-modulated grooves to modulated grooves. This is different than using an non-grooved section of the run out area. We still don't know the differences between a smooth surface and a groove because we do not know what is on the bottom of every stylus tip and that would affect how it works.

And a note, the inner radius of the record requires less anti-skate than the outer radius. We should know this because of the higher tangent angle at the outer radius without having to do the math.

Lastly, why doesn't someone build and market that measuring tool. Cripes.

 

Thanks for those- brings back memories of reading "Audio" magazine back in the early '70s here in the States, which I think was probably the best of the mass market magazines published Stateside (at least among the ones I remember, including Stereo Review and High Fidelity). There was a fellow, Richard Heyser, who used to write for them, often very technical, but interesting - i believe he passed away at a relatively young age.

 

The actual skating force if a function of the friction of the stylus on the vinyl and the geometry of an offset headshell. So if there is NO friction there is NO skating force. Also for a linear tracking arm (with no offset) there is no skating force. All this discussion about using blank tracks, or deadwax space CAN'T work because the friction will not be the same as the stylus in a modulated groove.
Additionally, at 45 rpm I would think the friction would be greater and one would need more antiskate compensation.

 

There was a thread on VE some years ago about a poster making the same hinged device as Shure showed used to test skating/anti-skating. Basically the cartridge head could swivel and if the skating force did not equal the anti-skating force it turned in one or the other direction. From that post the dead-wax method was closer to the truth than using highly modulated test tracks. Can't find the thread now though.

 

I use the earliest AT-PL120 and also an AT-LP120-USB and neither have anti-skating issues. It is true that AT pretty much eliminated the anti-skate system, but then put it back. If you have one of the AT-LP120's with a disabled anti-skate, they have a kit with a different spring in it. Of course you'll need to be able to handle a screwdriver.
Not having an anti-skate is not a big problem. Many turntables never had one or even an adjustable one. My 1970's QRK radio station turntable doesn't use one although it has a jewel-suspended, tubular S-style tone arm. I've never had a record skip and my records all play as good today as when they were new over 60 years ago.

 

Did you read the articles posted? They tested different velocities and showed little to no difference in the skating force.

Which makes sense in hindsight because there are two directional forces at play, a straight pull and a tangential pull. The difference between them will be the skating force. Increasing the velocity of the spinning disk will affect both of those friction forces equally leaving you with the same or close to the same skating force.

 

Sorry but this is just factually wrong. There is only one force and that is the friction force of the stylus in the groove. Maybe that is what you mean by straight pull. Anyway, the skating force is simply the component of the friction force that points inward.
Only one force, everything depends on friction.

 

Right. Sorry, one source of force.

 

I’ve been doing more testing in this lately and have found that setting my anti-skate via modulated test tracks, the dead wax result is that the stylus more or less stays put.

I have also found that Shure’s suggestion to match anti skating to tracking force is about where my modulated test tracks excel.

I may be prematurely wearing the outside of my gem, if Schroeder/SoundSmith are correct.

 

If you look at Fig 7 in the Shure article, you can see that the skating force is higher for higher velocities. Others have also seen that very high modulated grooves show more skating force. What can be seen is, except for the stick-slip friction between stylus and groove, that there is an increasing force to move the stylus sideways with high modulation. So where does the counterforce come in to the overcome the suspension force? Dissipated entirely in the suspension and/or an increased friction?