I had the same problem with a DC-1 about 4 years ago. I sent my unit to Lexicon for an upgrade to ver 4. When I got it back
I had a buzz, returned it to Lexicon 2 times and each time
they could find nothing wrong. My only cost was shipping the unit, which was not exactly cheap, back 2 additonal times and the long delay having my down
I just happened to touch one of the inputs and heard the buzz
I called Lexicon and they told me to ship it back again, I
said no way, I got it fixed in Denver, I believe for less than $100. It was fixed in 2 days. I would not spend $425.
I have traded the Lexicon for an EAD. I like the EAD a lot
better than the Lexicon, particularly when playing music.