I use the 600-ohm balanced DI to send my sound to the board at gigs. I was getting a nice clean signal until a couple weeks ago. Even at low volumes, the signal coming out of the DI suddenly started to "overload" the board, and I was getting a loud 'hum' out of the DI. Almost sounds like feedback. But the sound going to my speaker(Mesa 15" Powerhouse) has been unaffected. I pulled the DI jack out to see if there was a problem with the connection but everything looked OK. I called Mesa and they said I would have to send it in. I am trying to explore all avenues before having to do this. Note: I did re-tube it about 2 months ago but like I said, the sound coming out of my speaker is mint. Anyone come across something like this before?