Some thoughts on dust covers

@lewm

I thought you made your position clear in your first post, no need to say any more!

You are right - electrostatic forces are orders of magnitude more powerful than gravity. Another way to create static charges is to rub vinyl with a diamond stylus. Those charges immediately attract dust. Interestingly about 30% of dust extracted from records is diamond!

In my opinion the OP raised a good question - should the dustcover be raised or not when playing a record. Clearly this presupposes there is a dustcover and that it is hinged. If your turntable does not have a dustcover, or the dustcover must be removed when playing, this topic is not going to change anything for you.

I read up about the Wilson Benesh GMT One System turntable, which weighs almost half a ton and uses lots of materials science, university types and research grant money to minimise unwanted resonances. This behemoth does not have a cover, although it costs house-money! Obviouly they don’t worry about airborne feedback, or dust!

For the record (sic) my dust cover is hinged to an outer plinth which only connects to an inner plinth via the sandstone blocks they stand on. Otherwise there is an air gap, a bit like a double-glazed window.

Stylus rubbing on vinyl is not a cause of static charge. This was shown by Shure Corporation in their published white paper on static charge. I and some other guy here who also owns a static charge meter have repeated the experiment with the same result. No cigar on that idea.

My position has been stated twice already. I use no dust cover during play; I completely remove the cover, if the TT has one. But I advocate that each of us should make his or her own decision. My practice is based on my listening tests and my subjective opinion of what sound best. I do agree it’s a fine idea to cover the TT when it’s not in use. For the past many years I’ve had 5 TTs up and running with 6 different tonearms and cartridges, 3 TT s feeding one system and two TTs feeding another separate system.

@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.