Evolution ain’t what it used to be!
But you can still have a laugh!
Some thoughts on dust covers
Over the course of time there have been many discussions concerning the subject of dust covers. They tend to revolve around the central question: Should the dust cover be down or up while playing records? Some of these discussions have been nasty, consequently I have refrained from participation. It is hoped that I can provide some common sense that was given to me by someone of unquestioned authority many years ago. During college and after, from 1970 to ~1980 I worked in HiFi retail, selling high end lines of audio equipment. One of these lines was Thorens. Sometime around 1977 or 1978, if memory serves, Thorens introduced their new TD126, as a top of the line TT with their own arm and I sold the first one at our store to very good customer. He came back very unhappy after the first night of frustration with it. The problem was that with the dust cover closed some of his favorite records were hitting tangentally on the very back were the platter came closest to the dust cover when it was in the closed position. I called the manufacturer's rep and he set up a three cornered phone call with himself, the Chief Engineer of Thorens at the time, and me. I don't recall the man's name, but it doesn't matter, it is what he said that matters, then and now. The Chief Engineer explained that the problem was caused because the hole in the offending records was slightly off center so there was an eccentricity as such a record rotates about the spindle. The solution was simplicity itself, the dust cover should be removed always when playing records. That the intent of the cover is to protect the turntable when not in use. I pointed out that we lived in a semi-arrid environment (San Diego, CA) which is dusty to which he replied that if the environment was too dusty for records it should also be considered unhealthy for people to be breathing the air. He recommended are filtration, not dust covers to address environmental concerns. The rep asked about air bourne feedback from speakers and the Thorens guy laughed and said that if that was a problem in a given system, relying of the dust cover was a very flimsy and ineffective solution and that proper measures should be instituted to provide meaningful distance and isolation to ameliorate the problem. So the often offered extremes: a) Always play your records with the dust cover down, or b) put the dust cover away in it's box and never use it, should both be recognized for what they are are - not solutions at all. First principles: Identify the problem(s), seek solutions and alternatives, prioritize.
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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. |
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