I used my Aguilar db680 last fri at a bar then on sat at a different bar. Sounds great. Last night (tue) I went to use it in another bar and it died. I turned it on and it sounded a touch midrangish and after 2-3 min it started to distort and then when quiet. Today I tried it again and the same thing. Ive done the normal run down (cables, plugs, bass, speaker) and put a different preamp in the mix and everything is fine. Any ideas?