I have a Fender Bassman 60, but lately it seems to hum sometimes. The two basses I run through it mostly are my Jack Casady and my Yamaha BBN5II. Both of these basses are quiet, especially the Yamaha. When it hums, you can notice it as soon as you turn it on, so; could it be the electricity in the house? This amp and either of these basses have never given me problems before. The odd thing about it is that it only happens on some days. As far as I know nobody is running any kind of heavy appliance nearby. Also, this just started happening lately. Any ideas? Thanks, Mike J.