I don't normally use effects with my Fender P through my SWR SuperRedhead, but I'm currently using an Akai Deep Impact SB-1. I keep the SB-1 in the effects loop, but it is normally turned off. I use cheapo 10' long shielded cables in the loop with the Dry/Wet mix nob at 12 o'clock for a 50/50 blend. With the SB-1 off I've noticed that I get a much better tone with the effects loop set 50/50 versus puting the effects loop to 100% dry or 100% wet. Blended 50/50 the sound seems to be thicker with more bite and a more pleasing high end tone. How can this be possible? I'm wondering if the wet signal has a slight bit of phase shift that is thickening the sound? I should also mention that the gain increases a bit at the 50/50 position...and that always sounds better.