Audio Systems: Loud Cracking on switch off, pedal steel guitar, amp off

Question
Hello Robert,
I use a 75 watt Peavey Studio Pro 112 amp for my pedal steel guitar. It is set to give maximum "reverb" as this is required for the pedal steel. When I switch off after playing, there is a loud "Crack" sound. It makes no difference when I turn down the volume and or the Reverb before switching off. Is there something that I am doing wrong, I am concerned for the speaker. Your help is much appreciated.

Answer
The reverb is probably returning though an open bus which means that volume only works from the send but not the return. Generally there is supposed to either be muting or a gate to prevent that from happening. Try turning the reverb down before switching the amp off.