I looked around and couldn't find anything on this, so I thought I might aswell ask.
This may seem like a really dumb question, but, if you place cold cathodes, or even LED strip inside a tube amp, what is the chances of having interference? I'm aware using LED's could possible not interfere at all, but I'm just wondering this, as after I've got a few debts paid off, I'm ordering an Engl Fireball 100W, and think some green lighting through the front grill will look the dogs bollocks! Cheers!
Now, if you introduced some very large magnetic fields, you could perturb the momentum of the electrons in the tubes, or a high energy X-ray source, you could scatter some e's. LED's won't do any of that . Incandescent lighting shouldn't interfere at all, either.