Don't these use a "wall wart" power supply? Try swapping those around to see if that narrows it down. Usually power tubes can cause hum, not preamp tubes. My bet is a bad ground or a filter cap issue.

I've tried different ac adapters and different plugs at different venues. Still the one still has a hum. I guess the next step to be to get one of those little single plug ac power cleaners from guitar center.

Hopefully that will help.

Probably won't help this. Being that the internal guts have to have additional power supply conditioning to rectify the wall wart's juice for the tube circuit, my bet is a bad capacitor in that section.
Good luck!

Any chance it is still warranteed? In the end they are only thirty bucks so it is a big chance to replace the tube at 33% of the total cost and not have it work because it is in fact a capacitor.

jg49 wrote: Any chance it is still warranteed? In the end they are only thirty bucks so it is a big chance to replace the tube at 33% of the total cost and not have it work because it is in fact a capacitor.

Yea it should be under warranty still. I'll have to get my paper work on it out.

I'll just see if they can send me another one....For the price of the one that works I am really impressed with how they warm up my vocals through my PA.

maybe a ground loop?