So, to run from your top (ie: head) to your speakers (ie: cab) you can use this:
http://store.daddario.com/category/146498/Classic_Series
If you've been using a guitar cable, that could be a good place to start. The wires could be heating up just a bit so they have deteriorated over time.
That said, I was in a shop where a guy was fixing an amp that was having volume drops (but it would drop and stay dropped). The problem there was in the amp's power supply. :(
I would borrow a guitar and cables (if you need to) just to isolate the amp from (or as being) the problem. If you do that and have the problem, it is likely your amp.
If not, pull any pedals out of your chain. Change the parts that are left one at a time (guitar through existing cables, if that's not the prob, put the old guitar back, try changing the cable. Do one thing at a time until you isolate the problem. It's another good reason to have a back up of everything you use.
...so ever since then, I always hang on to the buckle.
