Dust cover up or down?

VPI Classic, custom cover fully off when playing, back on when not.

Pro-ject debut III, cover with hinges, up when playing, down when not.

It really has a lot to do with the design and quality of the TT and cart.

I've used my Linn LP12 since 1984 WITH the dustcover on. I LOVE the dustcover!—it allows me to leave records on the platter overnight. And I cannot hear any sonic problems its causes –  up or down.  

herb

"Can’t think of a single ultra high end TT that has a hinged cover? Would love to know if there are any?"

The VPI HW-40 comes with a hinged dust cover. The price new of the table is $20,000. Is it considered high end? I would think so.

I think with a fully suspended table like a Linn LP12 the dustcover is less likely to color the sound, but with a non-decoupled plinth it’s much better without the cover or at least with cover up. I have seen the static attraction effect at work myself so that’s another reason to go up or off. My WTT/TA has an unhinged “cake cover” so it gets removed for playing every time. I once had a Technics SP12 with a heavy rubber plinth and the dustcover really degraded its sound quality when down. 

It is inconceivable to me not to have a dust cover. Seems absurd to leave a tonearm with super-fine manufacturing tolerances, precise movement subject to dust or any airborne substance, often invisible when not in use. Irresponsible of OEM's not to provide them IMO.