My DSL 50 was sounding a little off recently so at my bands last practice I switched the power tubes out with a back-up pair of Groove Tubes. This fixed the muddy, undefined issue but after about a half hour of playing I started to smell that plastic getting really hot smell... I took a look at the tubes and all seems fine, they're the same brightness and all. I'm just wondering if this means I need a bias or if its just the tubes being broken in. Both sets were EL34's and ive heard that when youre using the same type of tubes you can get away without a bias. Thoughts?