I sent the following message to Eden's customer service: "During two gigs this month my amp starting making a very loud high pitched sound and sometimes random noises at random times after about a half an hour of playing. I've had to turn off and on the amp to stop it. The setup I'm using is a Eden WT550 with a S15D BagEnd cabinet. Is this a tube problem and how can I check it? Thanks youfor your assistance." And they responded with this: "Id suggest asking this on theeden-electronics web forum. http://www.eden-electronics.com/forum/default.asp The moderators there have more technicalexperience with the amps than we do here at the corporate headquarters as notedin this press release." Before USMusic bought them I could always get an answer out of their customer service. Well anyway, can anybody tell me if this is a tube problem? Thanks.