I finally have a nice, well working solution to one of my gear "problems": Independently adjusting the sound and the volume of two basses with two amps (one of them is a combo) and mixing the preamps, then re-distributing the signal in a meaningful way so the signal of both basses comes through both speakers. Now, my current setup looks like in the attachment The effect return in the iAMP 800 can be used to mix in another source, like a second pre-amp. However, the input is not very sensitive, so in the past I had a hard time using most pre-amps. Therefore I go into the Ebtech that does the signal level shift that I need and de-couples the amps from each other. I can turn off the GK with the iAMP on and I do not hear a loud "pop". So the transformers do a good job decoupling the amps. Also, there is no ground loop, thanks to the Ebtech.. The mixed signal can now be taken from either the headphone out (need special cable - stereo plug out) or the DI out, back into the Ebtech, out into the power amp of the GK. This way I can independently control the EQ on the two basses and have the signal routed through all three 12" speakers. With the master volume of the iAMP I control overall volume, with the master of the GK I control the GK volume and I can blend it in an much as I like. Anyone else has an unusual setup like this?