Re: distortion pedal on dirty channel
If you got a more modern Marshall (TSL, DSL, JCM 900) with the dirty channel with a good amount of gain and then a gain-dimed metal zone in front of it, its going to sound like mush. What the trick is to that is either getting a slightly dirty amp and putting an overdrive pedal in front that will push the amp into clipping (pedal should have high volume and medium gain levels). Or you can put a crunch/overdriving amp with a tube screamer type pedal that can boost the signal for solos. And as mentioned, give a slight different color to your tone.