FWIW, I've been investigating the McCormack lines looking for an amp for another system. I suggest you do some research as well. There have been considerable conversations about failures of an input board in the DNA .05 and DNA 1 model amps. I don't know if this could be your problem but if it is you may not want to pursue repairs. One of the posts in a thread is from McCormack describing the problem and why it is in their opinion not 'repairable', at least why they will no longer do so anyway.
Good luck............