Dust cover up or down?

I have a Technics 1200G.  I've always played with the cover down.  For my own satisfaction, I'm going to try with it up and off to see if I can hear a difference.

A proper dust cover is a big plus for a turntable both sonically and for protection for records and tonearms. What is a proper dust cover?

@herbreichert has notice no problem with his Linn. @fbgbill I do not know if you think a Sota Cosmos is a high end turntable but it does have a dust cover and like Herb's Linn the Sota's dustcover is isolated from the turntable, tonearm and cartridge which are floating on a separate sub chassis.  That is the most important criteria for a proper dust cover. It can not directly transfer vibrations to the working parts of the turntable. Used like this a dust cover actually improves the sound by attenuating the sound that gets to the cartridge like wearing ear muffs. In a system with Electrostatic speakers the improvement in detail is noticeable. 

This leaves a lot of turntables out in the weather but, there is a solution that can be used with any turntable. You have a baseplate made that is larger than the plan view of the turntable to which you can hinge the dust cover. The baseplate could be made out of wood, acrylic or even granite. There are plenty of companies that can make a dust cover of any size. You place the turntable on the base and the dust cover closes over it. I'm surprise there is not a company that makes the whole rig.

I am not the only one who thinks this way about dust cover. In an email conversation with Mark Dohmann he related that he was working on such a dust cover for his Helix turntables. 

@jagjag , unless you live in an industrial clean room there is no such thing as a dust free environment. Another issue is there is no such thing as a static free record. There is always a slight charge on records. Even if you ground out the record with a dead short within a short period of time the record will develop a charge. Why? The paper label and PVC are at opposite ends of the triboelectric series. Electrons migrate from the paper label to the vinyl giving the paper a slight positive charge and the record a slight negative charge, more than enough to collect dust. During play the record also develops a little more of a charge.

FWIW I have a VPI HW-40 and even though it has a hinged dust cover, I do not use the hinges. When I play, I simply take the cover off and set it aside. It goes back on after I am through. That is a lot better than dusting around the top of the table all the time. 

Mijo, I am trying to understand the structure of your Cosmos. Am I correct in thinking the cover hinges to the rear of the wood that forms the visible outer appearance of the TT? And you’re saying that the wood plus dust cover are isolated from the works by the spring suspension? If I’ve got it right, doesn’t the peripheral edge of the lucite also contact the wood, on at least 3 of 4 sides? Or is there a spacer that keeps them apart?

There doesn't seem to be much concern about the dust itself-- which is bad for your turntable-- it gets everywhere-- and bad for your records. It gets in the grooves, creates ticks and pops that are not always easily removed with cleanings. 

Some turntables should be used with the cover completely removed while others, like a SOTA Star Sapphire are designed to work with the cover on and closed. So like most things audio-- it just depends.

The least good thing to do is leave the cover on and up during playback.

I use a fine quality paintbrush to dust off the platter between plays, and the plinth every few days. Dust accumulation is bad for your gear.