I can't explain it technically, but I can from a. guitarists' perspective.
Anytime you use effects pedals (especially O/D or distortion), you get that noise. Most guitarists, including me, handle this as follows:
In a live performance, I use a Boss Noise gate pedal. It goes in line with your pedal chain and strips away the noise. You have parameters you can tweak to get just the right amount of elimination without eroding the effect too much.
When I record, I use noise gate software to do the same thing.
The thing I like about this builds I can make the circuit sound a lot different simply by playing with the Gain, Then and Volume pots, and also changing choice of pickups on the guitar. The guitar also has its tone and volume controls. So, with all these variables, it's easy to get different colors to your sound.