Dust cover up or down?

Some people have very strong opinions on this but mine is that, as is often the case, it depends. Not all dust covers are affixed to the turntable in the same way and left on during play some can transfer vibrations back to the phono cartridge. Others, such as the dustcover on my VPI TNT III, are completely independent of the plinth, so that's less likely to be an issue.

Back in the '80s, I had a Denon DP-80 turntable in a VPI HW-9 two-arm base. One problem I had with it (and that really took some sleuthing to resolve) was that static electricity from the dustcover was enough to decrease the VTF of either arm. So I always used that with the cover off.

Cleeds, now that is a new one to me (dust cover reduces VTF by electrostatic attraction). How did you figure that out, given that you can’t measure VTF with the cover down?

Or I guess you could, by raising and lowering the cover with the scale in place that you could read through the transparent cover.

@cleeds is right, i remember a Dual having that problem, rub the cover with a cloth till it pulls the headshell/cartridge,arm up. Good game.

Never experimented that on another tt.

Fascinating.  I would not have thought the attraction would be so strong over what would typically be the ~6-inch distance or so, between cartridge and dust cover. So ES on an LP can spuriously increase VTF and ES on the dust cover can lower it.  If you're lucky, the two attractions are equal and there is no change in VTF.  So one other solution is to rub up your LPs with a wool cloth before play with the cover down.