msb problems?

I have a link 3 and just purchased the 24 bit upsample I was very satisfied, I have a pair of Aerius speakers so I hear any and all changes but this one was dramatic, then all the sound improvements went away I sent the unit back to msb for repair and they found nothing wrong with it and sent it back, yes sound does come though it but there is no diff from listening to my cheap sony cd player buy itself,I did hook it up to other systems of my friends with the same results,and help? The people at msb have ears but cannot hear and I now have a dac that is usless to me after spending $700 on it, right now I am too upset to even talk to the people at msb.Help!