I should probably put this in Good Housekeeping but I feel out of my comfort zone over there 
Our new(ish) cat seems pretty clean and well trained but I'm finding that the house absolutely stinks
.
We can't find an obvious source. It's not like there are damp patches or puddles of wee.
Sometimes it smells faintly of cat wee and sometimes it's a more general musty unclean smell (even though we do clean the house - honest!).
Is it other cats coming in and spraying? Does cat spray smell just like cat wee or is it different?
Are cats just generally a bit smelly 
Any tips?