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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.

billstevenson
ricmech23
107 posts
 

My Pro-ject tt user manual specifically states the dust cover can pick up resonance from the loudspeakers and pass those resonances into the plinth, therefore remove the dust cover while playing. 

richardbrand's avatar
richardbrand
213 posts
 

It is pretty obvious most turntable manufacturers would rather not have to deal with dustcovers!

Thought I'd try to measure the attenuation from my cover, so I dug out my Denon Audio Technical CD and played some test tracks.  At the same time, I ran a Sound Meter application on my Android phone and put the phone on my platter mat near the pickup.  I could watch the phone while raising and lowering the dustcover.

On 1000-Hz test tones, the attenuation was about -13-dB with the cover down, while it was only about -3-dB down on white noise   On pink noise there was barely any difference!

I must point out that my plinth and table lean towards the massive side.  The more the mass, the less the amplitude generated by a specific acoustic energy level.  I find it interesting that Pro-ject don't want airborne vibrations to enter their plinth from a dustcover, but are presumably happy for them to enter the platter directly.

Acoustic feedback might make for nicer sounds, and could even explain why so many like records.  But it does not make for accurate playback if that is your thing.

lewm
13,150 posts
 

I don't know why I keep posting on this, because it is one of those questions where every one of us is already convinced of the efficacy and rightness of his or her current practice.  We are all pretty much old farts and set in our ways.  Suffice to say, what I have already said, anything anyone else wants to do is fine with me.  I am operating based on my own past experiences, and so probably is everyone else. But please please don't accuse others of (1) not having a system good enough to hear what you hear, or (2) being a Philistine and so able to tolerate the horrible problem that you have seen fit to prevent.

mylogic
26 posts
 

Am l am correct in thinking that Rega and Project turntables are light weight minimalist designs? They certainly look like featherweights in the hi-fi boxing ring….

Maybe that’s why they shy off covers? Highly likely they already know that their design structures are not massive enough to resist external forces unlike decks with heavier more substantial plinths.

 

 

sjbellers
22 posts
 

I have two turntables, and I like both. A Sonograph  SG-3 and a Kenwood. Both have dust covers that I use to protect the TT when not in use. I had noticed the acrylic dustcover material would attract dust to the cover and would sift through the crevices in the dustcover hinge joints. I ended up solving this by getting a destat source from Amstat Industries to produce a charge to counter the electrostatic attraction of the Acrylic. It is a polonium 210 alpha emitter fixed in a bar array, and gets two sided taped to the inside of the dust cover or base of the TT. Works well; is safe. Not inexpensive because it needs to be periodically replaced as it decays off and looses its effectiveness. but it does destat  the dust cover and everything under it including the vinyl record.

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