Crackling noise from one channel after a couple hours of use

[laphil]

I have a crack with speedball upgrade. I’ve been using it happily for several years now. One thing I noticed is that when I use the amp for a longer time, 2 hours or longer, a crackling noise comes in on one of the channels. When I turn it off for a while and turn it back on, the noise goes away.
I always have had the rubber feet on since the completion of assembly and the amp is otherwise quiet.
I’m guessing some components get overheated after an extended use. Is there something I can check/change/upgrade so that the amp works without noise even for longer listening sessions?

[Paul Birkeland]

This could be a flaky solder joint acting up when it's warm.

What we recommend is that you plug in a cheap pair of headphones to the Crack, the poke around in the circuit with a wooden chopstick while it's running and listen for any noise through the headphones.  If you are able to make noise by pressing on certain joints, that will help to focus your resoldering efforts.