I know it's not a bass amp, but I thought you tech-heads might know. I bought a little 20W ashdown valve combo used from a local music shop a couple of months ago, and today it's started making a little rattling sound when playing, or if i tap the amp lightly... It's pretty irritating, and it's coming out in recordings as well. It only makes the sound when the amp is on, not on standby or when it's off. Any ideas? I thought it might be a loose valve or something, but seeing as it doesn't happen when it's off, it may not be?
EDIT: sorry i just realised this should probably be in technical issues, feel free to move it, mods.