Strange bassy feedback from channel 1

[scott7d]

Over the last couple practices, I have been getting a low, bassy feedback from channel one. It starts off quiet and builds up to rattle the cab, and then starts buzzing real bad. It does this even if my guitar volume is rolled back.

Could this just be a preamp tube that needs swapped? It does it on the other channels only if I switch over to them while the feedback is happening, but otherwise, it won't start on it's own with channel two and three. I hope that makes sense.

And on an off-topic happy note, I finally gave the II C+ mode a well deserved chance, and WOW. I am going to have a lot of trouble deciding which mode to use!

Thanks!

 

[phyrexia]

What power setting are you using, how loud are you playing, and what is your reverb set to?

 

[scott7d]

I am using 90 watts, and not playing very loud. Just enough to mix in well with drums and bass in a small practice area. Reverb is around 12:00. Also, it seems to want to do it more on fat and clean, and not so much on tweed.