What's this sound upon shut down?

[Mr. Blues]

My Mark II C+ is making a strange new sound when I shut it off.
It's a sort of low volume "DOOOooooooooo"....that fades.
The amp sounds great otherwise. It never made this sound before.
Is it anything to be concerned about?
Thanks for all replies

 

[MrMarkIII]

Your amp is haunted by one H.J. Simpson.
But seriously, does it still make this sound if you put the amp on standby first?

 

[Mr. Blues]

yes....standby....then power off....."dooooooooooo" (fade).... it's not very loud

 

[Boogiebabies]

It's the filter caps discharging to ground and the remaining signal is bled through
the speaker. It sounds like flatulence in most cases. Some do it with old caps, new caps and some don't do it at all. It's just how it is.

 

[Mr. Blues]

Many thanks!!!

 

[Boogiebabies]

One trick to stop it from happening is to turn up you master volume slowly to 10 right after you go to power off.

 

[RectoFreak]

To prevent this from happening to me, I put the amp in standby and wait 30 or so seconds before powering it down.