Dustcovers that remain attached to the table usually do affect the sound detrimentally, whether played with the cover up or down. I have one that fits over my Basis table, so it must be removed completely to put on a record. I no longer use it at all because of the incovenience.
To keep the platter from collecting dust (which would then contaminate a record), I use a "sacrificial" record as a platter dust cover (a Charlie Rich record someone gave me). The rest of the table gets dusty, but, that can be cleaned off occasionally. When I was actually using the cover, a lot of dust still managed to collect on the platter, so, the record-as-dust-cover was still a good way to reduce dust build up.
I use a microfiber dustcloth to wipe down the platter once in a while. I keep the platter very clean because my table uses a vacuum clamp that firmly pulls the record surface into contact with the platter surface.
To keep the platter from collecting dust (which would then contaminate a record), I use a "sacrificial" record as a platter dust cover (a Charlie Rich record someone gave me). The rest of the table gets dusty, but, that can be cleaned off occasionally. When I was actually using the cover, a lot of dust still managed to collect on the platter, so, the record-as-dust-cover was still a good way to reduce dust build up.
I use a microfiber dustcloth to wipe down the platter once in a while. I keep the platter very clean because my table uses a vacuum clamp that firmly pulls the record surface into contact with the platter surface.