Sony double-din problem?

[jessdabest77]

I have a Sony XAV-60 double-din and installed an amp and sub to it,and the problem I'm having,is every time I turn up the volume pass 23,the stereo goes off,then turn's back on.The deck goes up to 40,so I thought it might be the sub pre-out on the stereo.so I tried connecting the RCA jack's to the rear pre-out's on the stereo,and did the same thing.It never did that before I had the sub and amp to it.I'm stumped,any clue's guy's,thank's.