Hi Janek,
I've just got hold of a 5 year old Clover Apeiron H4 which is in excellent condition.
I'm getting a hissing noise after playing for a while i.e more than 1 hour.
I've cabled the bass as follows;
Bass into a Sansamp RB1
From RB1 thru a rackmounted tuner to a dbx166xl compressor/gate...