Ok guys

And please do not tell me about dust, nobody leave vinyl on the platter longer than one side, often just for a few songs and then it’s back to the sleeve on the shelf. So WTF we need dust covers for ?

The concern, IMO, is that static charges on the record could pull dust particles that are on the platter into the groove of the side of the record that is not being played. And when the record is turned over so that the side which had been in contact with the platter is then played, sonics, tics and pops, and record wear may all be adversely affected as a result.

...nobody leave vinyl on the platter longer than one side, often just for a few songs

As one who listens primarily to classical music, when I listen to a record I usually listen to both sides in their entirety.

Again, though, I do not doubt that removing a dustcover is sonically beneficial with many and probably most turntables. My earlier comments pertained exclusively to the SOTAs.

Regards,
-- Al

@chakster
I always appreciate your enthusiasm for Technics tables and vinyl playback. I keep the transparent hinged dust cover on a KAB mod’d SL1210M5G down and have no problem seeing the record currently playing. Even with nothing on the platter, leaving the cover in place limits dust reaching the mechanicals of the turntable and should keep the mat cleaner too. FWIW - in addition to changing the stock feet to threaded spikes resting on a heavy wood platform with layered isolating materials under each corner, I also use small gel "bumpers" on the plinth where the dust cover will rest when lowered. Finally, a weight is placed on the top of the closed cover during playback.

As Mapman has already said in response to the OP’s question...up or down? Try it both ways and let your own ears decide.

Alright then
Yes you can tell I am not at work this week as have time to try various experiments but I do think this one maybe useful to some.
Or at minimum another point to discuss?
Re static build up on the record surface while playing.

So we measure static on a fairly regular basis on the films we produce during manufacturing and to this end we use various makes of fieldmeters like the one in this link.
https://www.simco-ion.co.uk/our-products/static-measuring/electrostatic-fieldmeter-type-fmx-004

Well I dragged mine out and checked the charge on the record surface while just spinning with no stylus contact and then during and after the full side of an album had played.
Now maybe my meter is not accurate enough to monitor very low level change ( tbh I have no idea what levels we are talking about for the "build up" on a record surface?) but I could measure NO difference in my system in my house with my meter.

Hi Uberwaltz,

Is the room air conditioned?  Especially if it is not, I'm thinking that the humid conditions which tend to occur in your neck of the woods may result in lower static levels than in more northern regions, at least during the cold weather months.

Best regards,
-- Al

Al
It's "only" 82 here today, no need for the AC yet.
But that's a valid point especially if the amount we are talking of is a very small amount, and that I do not know the range of?
When i conducted my test it was fairly mild in the room, low 70,s? Did not feel particularly humid but must be in relation to cooler states.