SRRI hiss/noise

[atomicsuperfreak]

Need some advice here - I've got a Super Reverb reissue. When closely mic'ed, there is a very noticeable hiss/noise coming from it. If I listen closely enough, I can hear coming from the amp, but it's definitely much more noticeable when mic'ed up.

Any thoughts on what could be causing this?

 

[atomicsuperfreak]

Hate bumping threads, but.... bump. Anybody have any ideas?

 

[Bucksears]

Mine does something similar; basically just sounds like more 'air' coming through it. Volume all the way off, nothing plugged in to it (or when a guitar is plugged in). Not a hum or buzz.
Don't know what it is, might be power filter caps?

 

[atomicsuperfreak]

Here's what it sounds like: