So i've had my Blues Junior for about 5 or 6 years now and i ****ing love it. It has seen so many gigs, been pushed around, and been played very loud.

about a year ago i changed the tubes because the sound was starting to get a little crackly. It sounded great again.

I've started gigging a lot recently, and just today it has started to play up. It sounds like someone is playing with my tone knob on my guitar, i've recorded a sample:

[forbidden link]

Anyone recognise this problem? The tubes look fine, the preamps maybe look a little dull, but they are still glowing.

Any help would be appreciated.

Light isn't an indicator that tubes are working. Start by replacing the tubes. You should have a replacement set anyway, plus it's the easiest and most useful diagnosis you can do.
have you ever changed the tubes in 5 years? ever?

change the tubes. its time.
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