Thank you Teemuk

I've got a question regarding the fender Pro 185. I think it's a great amp with tons of features and very warm for a s.s. amp.
It has two channels plus a boost. Here's the problem : whenever I set the boost louder than the distortion and go and shut off the amp there is a volume swell even if I'm in the clean channel. In other words say I'm using the clean channel set to 3 and go and turn off the amp and the boost is set to 5 as soon as I turn the amp off the volume swells up to boost volume.
Is anyone having the same problem? Please help. Thanks