I think I've hurt my amp!
When I play the low E I get a horrible whooshing noise, only that string?
Can't see any obvious tube damage has anybody got any ideas?

Hi ford
I've got the same amp...and the same problem...orrible noise only with the low E string.
I don't think the problem are some microphonic tubes(i already changed the originale tubes)...maybe trouble is in that iron tube support vibrating when you play lower notes.
Try playin' while a friend "stop" the tube iron support filament(take care...tubes are damned hot!)....once you noticed the troubled support...modify it by your hands to prevent vibrations
Many peavey C30 users have this problem....
maybe the amp project is not so good...but the sound is great.
Hope to be useful
chris