After some time, I now got the chance to experiment again with this project.
I'm testing my proto boards and I noticed a couple of interesting things, so (as always) your input is more than welcome
Both of the issues I noticed are DC-leakage related.
1) When I power up the unit, the audio output (after C101) reads about 400-500mV! This values decreases (painfully slow) and after 25-30 minutes it settles down to 20-30mA. Is this normal?
2) Also, I noticed that on the filter sections (points 22,25,23 on the schematic) I measure about 550mV DC and this doesn't decreases with time. Again, I don't think that's normal behaviour as there are blocking caps, but please correct me if I'm wrong.
The schematic can be found here