Discharging the Capacitors
People are always worried about discharging the capacitors in their amps. Yes, high voltage is scary and all that, but it’s really very simple:
Turn the amp on, let it warm enough to play through, turn it off. That’s it.
Here’s a video to illustrate:
To recap: Don’t put an amp in standby if it has one. Just turn it off. It doesn’t make any difference if you play through the amp, but it will verify that the charge is gone. And you can always verify with a voltmeter if you want.