I always remove mine because the vibrations in the cover impacts overall sound quality
The plinth should be free from all vibrations, so having a lid that can vibrate in sympathy to the music is causing those vibrations to be transferred
- into the plinth, down the arm and into the cartridge
- or into the plinth, through the main bearing and into the cartridge
- either way - it’s not desired
It’s easy to determine...
- get a stethascope
- place it on the lid while playing music
- if you hear virations - those are then getting into your signal via rhe plinth/arm/cartridge
You can also checkout if the plinth is vibrating using the Stethascope also
Regards - Steve