Do caps make noise if they're failing?
Sometimes they make noise if they are not failing. I've had brand new X2 caps buzz like you wouldn't believe.
I had a problem with all sorts of things around our house buzzing a few months ago. Turned out to be a failing power supply in an older TV. Once it was unplugged lots of things quieted right back down.
See if there are any large heating appliances on while you have the Felix plugged in, sometimes those can cause CMC's to make noise.
BTW, it looks great.
