This is why an effects loop on an amp is a good thing. If you use amp distortion, you really don't want to be using a delay pedal unless you send it through the effects loop, because the distortion gets out of control. Think about it: when you use distortion, the distortion happens when you play two different notes together. If the delay pedal is after distortion, the signals of overlapping delays don't interfere, but if the delay is before distortion, the distortion treats the overlapping delayed signals as being one big chord, and it gets muddy real quick. This is why time based effects should almost always be put after tone effects, unless you are going for a deliberate effect.