Quote Originally Posted by buttcheeks
can you tell me how old this amp is? And would you say that the motor sound kind of sounds like a "motor-boat?"
The amp is only 5 years old. I bought it last year, and as soon as I got it home I put in a new set of Svetlana tubes, and took it to a tech to get it checked out, and everything was kosher.

The sound is more like a noisy fan on a computer, it starts out relatively quiet and then "revs" up to a crescendo. I played it again tonight at practice and when it made the noise, I gave it a good knock on the side and it stopped. But it sounded like the tubes were getting microphonic when I bumped the amp, so I don't know. I'm afraid my amp is going to explode.