Thank you for the input. My primary concern about the hum is recording. I want to mike the amps in tandem for a cool ambient stereo effect. Since the hum is a part of the amp, it will be there even if I use a volume pedal or noise gate. Do you have any suggestions for making it unnoticeable in a recording (mic placement, perhaps)? I'm new to home recording. I'm sure there are tricks to dealing with the inevitabel hum associated with single coil pickups, analog effects, and tube amps. Buddy Holly and the Crickets most have found some solution!!
You bet there are tricks to recording Champs. There have been hundreds of well known recordings using Champs...'Layla' and 'Walk The Line' are the first that come to mind. Back then, the hum probably just got lost in the mix and they didn't worry about it.
I'm not an expert but a few things I can think of off the top of my head: Put the noise gate on the amp mics, not the guitar. Don't mic the amps too close. During mixdown, mute the channels that the Champs were recorded on when nothing is being played on those channels.
If the hum is unusually loud maybe you should get them checked out? or at least go back to the store you got them from and compare hum to other new Champ 600's. Chances are they will all sound the same, unless you got a lemon then you can exchange it for a new quiet one since you bought them new.