Toying around with a circuit to add tube distortion to line audio using 12AU7 aka ECC82 tubes. It hadn't occured to me before watching glasslinger's latest video where he restores a 30's mantle radio that one needs to add some kind of current limit to the filament supply. This because the filaments start out at a lower resistance, and without a limit there might be thermal shock and damage over time.. !elektronik