Mystery hum

Hi there, I've had this fender blues deluxe for 4 years now, I'm getting this hum every time I turn it on. Its not too loud but its very annoying, happens on both channels. Tried all my guitars and its not them, wondering whether anyone has had any experience similar to this or has any suggestions.
Cheers

It could be dirty power. I have that problem at home and one of the places I play.

Are all the guitars single coil? If so then it's the 60hz hum and there's nothing you can do.

Is there a dimmer switch nearby? If so this can create a buzzing noise.

Are the lights in the room florescent? If so this can create a buzzing noise.

Is there a fan in the room? This can cause a humming noise.

It could be "dirty power" or as I like to call it "polluted power" as Parma_TeleMon mentioned which can be remedied by expensive power conditioners and things. The amp being on an outlet/power strip with other things can also contribute to a "polluted" electrical signal

I have that problem with my ac30. It makes that hum without a guitar even plugged in. Drives me nuts.

It could also be a ground loop from your cable. Try disconnecting your cable (if you have cable in this room) at the wall and see if it clears.

How old is it? More importantly, how old are the filter caps?

i had a hot rod deluxe that developed a hum.. i moved the preamp tubes around and it helped a lot