Troubleshooting - Pepper spray

[buckle]

Finished it today. Took it to rehearsal and it just killed... until it popped and just made hum and nothing else. I took it home and there were no loose connections other than the jacks which I tightened up. Tried it again and it worked, but their was not nearly as much gain? Granted it was the difference between driving a tube amp and going through a USB interface, but still. Could I have blown a cap or diode? Also I can kill the volume with both knobs, which doesn't seem to be correct to me.