Its my Trace Elliot GP11 Mk 5 4x10 combo, and it only happens to the 1x15 extension speaker, not the 4 combo speakers
Power up with 1x15 TE extension cab attached and there's a big pop and at the same time the 1x15 jumps forward.
Doesn't make any difference if gain and master vol are zeroed or not
Its also very hissy, even with using the graphic, everything above 400hz turned to minus zero and all treble on the bass guitar turned off , still sounds like an angry snake. It seems like it's nothing to do with treble on the TE Graphic, or the bass guitar
The GP11 has a noise switch and i thought it might have stopped working, but when i switched it off the hiss got louder, so its working to some degree
The 1x15 TE cab works fine, but i'm seriously perturbed by the enormous jump ( and pop ) at power on, and the hiss
Maybe the TE 1x15 is just old and needs replacing ?