Hi Mike

I had some thing very similar happen with my concerto & smac set up .

The engineer over the phone adviced me to remove the audio cables L & R from the smac , plug in a pair of earphones into the earphone socket on the smac . can you hear any sound ..in my case i could hear it very clear and Loud .
The problem i had was bad connection in my audio lead .
If you get full volume from the earphones ..look at the leads , sockets on the smac or even your mixer !!

hope this is of help .

I went to to Texas accordion Convention , those folks were getting some very good sounds out of their Roland V accordions

Regards ..Giovanni