EDP and unwanted noises

["Luca" <lucafeed@tin.it>]

Hi,
since a few days my edp is knowing new noises (some I didn't ask for).
I tried to make some proofs:
input completely closed>record>stop>overdub here it comes the noise: it is 
a
low bump that comes at the pushing of the overdub and stays in the loop.
If I undo the noise goes away.
This is what happens after having swithced off and on again; before doing
this the same "bump" was also when record>stop.
Sorry to bore you, if there is a specific argument on LD's archive, please
tell me the path.

Thanx
Luca.