I have an SVT 4 Pro which I bought new about 12 years ago and it has worked flawlessly until about a month ago. I was playing a gig at the Ramona Mainstage opening for Gary Hoey and during the sound check the amp started cutting in and out. I changed guitars, instrument and speaker cables and finally just had to run direct into the house PA, which sucked by the way. The next day I turned on the amp at home and left it on for about 10 hours, randomly playing through it throughout the day. It worked flawlessly which made me think that the problem might have been the cable they used to plug into my direct out from the house system, which really doesn't make much sense to me. About a week later I did a gig at the county fair and it performed without an issue which made me sure that it was indeed the venue's cable. Well, I played another gig at a small venue a couple nights ago with out any cables plugged into the direct out and it started doing the same thing but this time it did not only cut in and out, it would also make my volume drop about 30% from time to time. Just to make sure my cabinet was not the problem, I played another gig last night using my backup rig with the same cab and everything worked fine. Any clues?