Some thoughts on dust covers

@lewn

Thanks for that Shure thing! I guess it is in a chapter from 1978 in high-fidelity-phonograph-cartridge-technical-seminar-faq.pdf entitled CHARGES ON THE RECORD--A STUDY OF STATIC ELECTRTCITY ON PHONOGRAPH RECORDS.

The only mention of stylus rubbing causing electrostatic charges seems to be "Incidentally, measurements with these instruments will also show that electrification from the direct friction between the diamond and vinyl is, oddly enough, negligible’.

The author created static charges initially by rubbing the record surface with cat fur (labelled CAR FUR in the table!) resulting in 30,000 Volts when the record was lifted from the table. Considering he switched cat fur for a more repeatable 10,000 volt probe, I am not surprised the stylus is regarded as a negligible (but not zero) contributor!

The seminar reinforced that the most effective way to temporarily remove static is to use a carbon-fibre brush. One was attached to the V15 Type IV cartridge but this approach seems to have gone the way of the dodo.

Saved me spending on a Zerostat!

Another surprise for me was learning just how much static electrical forces can change the tracking force!

All good stuff ...

In my informal "experiment", I first yanked an LP from its paper sleeve (in order to be sure it got charged up) and measured the charge on one surface, 11kV.  Then I treated that surface with my 40 year old zerostat and measured the same area again, 0.1kV.  Then I played the LP and measured the same area yet again, 0.2kV.  That is the definition of "negligible".  And the very small increase in charge density may well have been due only to my handling of the LP after playing it. However, you are not alone in your previous belief that the diamond stylus rubbing on vinyl causes static charge.  Several makers of the very expensive static charge removal devices (not the relatively cheap Zerostat) parrot this belief in their advertising brochures.

@lewm 

It seems the 30,000 Volts recorded by Shure corresponds to the breakdown voltage of air in a Californian winter - with a very low relative humidity of 10%.

Shure's measured voltage dropped dramatically when the record was placed on the grounded platter (much of the field migrated to the platter side) and returned as soon as the record was lifted.

Prima facie it seems that when you played your record, it doubled the charge so I am keeping an open mind on whether the rubbing stylus can create charges. Charges attract dust like crazy, and dust down to smoke-size particles and even down to a few microns may be significant.

If I remember, I now run my carbon-fibre brush both before and after playing to try to remove fresh dust before the records goes back into its anti-static sleeve.  I am still waiting for an ultrasonic cleaner to arrive from China!

In modern physics theory, electromagnetic and gravitational forces have hugely different magnitudes.  About 1,000,000,000,000,000,000,000,000,000,000,000,000 times different!  Which explains how plastic combs can pick up paper on a dry day, and charged records can significantly affect stylus tracking forces.

That Shure seminar was not too keen on Zerostat-like devices: "Another form of active ionizer is in the form of a pistol-shaped, device, which produces positive ions when the trigger is pulled, and negative ions when the trigger is released. This device is effective for large charges, but it is hard to avoid leaving residual charges on the record since there is no way of detecting the zero charge condition" which accords with your measurement.

"Prima facie it seems that when you played your record, it doubled the charge" First, 0.1kV to 0.2kV is a range where the meter is not very accurate and readings are not very repeatable.  The meter never reads zero, for example. So the difference between the two readings may not even be statistically significant.  Second, like I said, it is much more likely that my touching the LP had more to do with the difference, if it was even real. Third, such a low amount of static charge is inconsequential even if real. The problem we are addressing has to do with charges far in excess of 100V (0.1kV). 10kV (or 11kV in the specific case I noted) is 100 times higher 0.1kV. Do you have a background in this field, or are you a physicist or other scientist? If so, feel free to point out the error in my thinking. Since you don't have access to my meter, you could not have known its quirks, so I don't mean to criticize you for that.

I don't know why you compare "electromagnetic force" to gravity. First, the magnitude of the difference as you express it has no meaning unless you know the relevant parameters for the source of the EM force, in the case of EM, and the sizes of the objects that experience gravitational attraction and the distance between them, in the case of gravity. But also, electrostatic attraction is not identical to electromagnetism. The point about the Zerostat is only that if used properly it will reduce the charge to a harmless level. And it costs a lot less than most of the modern alternative gadgets.

Some flat earthers maintain that what we experience as gravity is due to electrostatic attraction. They have to resort to such an explanation, because if the earth were flat, it would not be massive enough to account for the gravity we do experience.

@lewm I don't know why you keep posting on this either--you've covered it soup to nuts and, at this point, you won't change anyone else's mind who disagrees.

@dwette Having a custom cover made of acrylic to protect the TT is not expensive--i had one made for my custom Jean Nantais table for $120.  I remove it when i play but i have a second TT, an old Sony DD from the 70's that has a hinged dust cover that i just put up when i play LPs and have both removed it and played LPs with it down and i can't tell the difference in any position, although i would probably unhinge it and remove it if that were convenient when i play LPs.