Hi Jose,
at first you should try to connect some 'empty' RCA jacks into the Paula outputs of your current machine. That should usually boost the Amiga sound signal again, since the Amiga kind of mutes the outputs when there is nothing connected. This also affects the audio signals on the video slot.
Also how old is your PIV and what revisions do the MultiBridge and the FlickerFixer have ?
Many older cards (the PIVs) need a rework to get proper sound output.
The next thing is, that the Concierto wasn't exactly a good design cause it has a quite heavy interrupt usage because of the relatively small fifos of SoundBlaster compatible audio chips (only 256bytes). I have had customers in the past with some A1200 towerized systems with 060 cards who weren't able to playback 44.1 kHz 16bit stereo wav files without stutter. Could you maybe try to to rip a cd track as a wav file and play it back through Concierto and tell me if it still stutters ? If yes, is this also true for a mono file in 16bit 44 kHz ?
So far
Masta