Im am not much on all this but i am learning ... here it goes. I use i guess outboard preamps both a behringers one the sansamp knock off BD121 i think the other the new pod v-amp. i like them both and the sansamp pedal has held up well giging and all i got great old school warmth when in my classic rock band with it...i use stricly passive Fender jazzes. Question: I used to run thru the standard passive input in both my Eden and GK rigs but lately i get a lot more ground hum this way but its not the pedals. I started going thru the amps return out by passing the pre-amp and all is quiet....what gives? Some say i have a bad ground wire in the pre but in two diffrent amp in two diffrent locations...i do suspect the wiring in both homes i play in. I bought a Morley HumX and it helped but returned it when i thought i fixed the problem...guess i need to go get it again. What harm could i do to my head by by passing the preamp thus losing the clipping feature. This scares me some but i know when i pushing an amp from the sound alone..i hope. I also hate losing the tuning mute button on my GK. I talked to a guy who is a pretty well known bass player in the area who said he has seen it done both ways and doesn't know of any harm using a return would cause thats what preamp outboards are for?