Sounds like a bad preamp, I've had my DR 500ME since Jan. 2009 - ESonic2 system sounds great but I can't leave the batteries in it or they drain. Your tuner work without the cable plugged in.
The electronics are warranted for 1 year by Epiphone, and if you registered with Shadow Electronics separately (they make the ESonic2 system) the electronics are warranted for 5 years by them. I returned the guitar to the dealer, they couldn't find a problem and then I contacted Shadow directly. Like you I loved the instruments sound and playability and didn't want to send it back to Epiphone, shipping fees, hassle, etc. so decided to let their warranty on the electronics expire and take it up with Shadow Electronics at a later date.
They told me all I have to do is contact them for return authorization and send in the preamp and they will send me a replacement. The system is awesome, and sounds great, I just haven't returned the preamp for fear of getting one that will have worse issues, based on the reports here, that began when the new system came out on the '09 models. For now I just pull the batteries when I'm not plugged into an amp or PA.
