I just bought a fender ultimate chorus amp(2x12" speakers-130w's RMS-solid state-used but in great condition), and I've noticed it doesn't hum at all when the guitar cable and guitar are not plugged in, but when the cable and guitar are plugged in; the normal channel hums very little(hardly noticeable) but the lead channel hums pretty bad. I use a fender squire vms, but the interior of the guitar is shielded. I was wondering if this is normal for a solid state amp, and if it isn't what could be causing this? It also makes a loud popping sound when I turn it off while still on lead channel, I end up switching to norm channel before I turn it off...