You might try adjusting the level going through the FX loop. The channel master acts as the fx loop send level and the Output control acts as the loop return level. Try running the channel masters lower and turning the output control up more to compensate for the lost volume. If that doesn't help, try the opposite, channel master up higher and output control lower. I also have a DD-20 (great delay pedal) and have not noticed any unusual compression from it. I'm running it in the loop of my rectoverb combo (modded to a serial fx loop... parallel sucked ***) at the +4db setting. Hope this helps. Good luck.