you probably know this, then again you might not. on the swr amps with the "side chain effects loop" that have the effects blend knob, you can input a signal from another source entirely into the effects return jack, and mix the signal with that of your bass. in the past i did that with other preamps, and on a few gigs i let a keyboard player plug into the effects return and dialed the blend to give a good mix between the two of us thru my speakers. not my favorite thing to do, but they were small gigs. recently i went to radio shack and picked up two adapters. one that had a male mini stereo jack on one end, and two male rca/phono jacks on the other, and a second one that had two female rca/phono jacks on one side, and a mono 1/4" male plug on the other. i hooked the rca jacks together. plugged the mini stereo jack into the headphone out of my laptop, and plugged the 1/4 mono jack into the effects return of my swr electric blue. that amp has a headphone out jack. now i can learn new tunes off of mp3's and play along to them any time of the day or night wearing headphones. the second thing i did a couple of days ago was inspired by an article i read about nashville session players in BP mag years ago. they have a bopx called a "mor-me" which lets them take a headphone mix and add as much of their bass signal to it as they want. i wanted more bass in my mix, and wanted it loud enough that i could stand in the room with the drummer. i sent a DI from the swr to the board. i also had a cab miced in the other room. i sent my effetcs send as a line out to a poweramp which powered the speaker to be miced. i took a regular 1"4 cable and plugged one end into the headphone out jack from the control room, and the other end into my effects return. i was able to use the effets blend control to mix between the regular headphone mix being sent to me, and my bass signal from the amp/ the swr wasnt powering any speakers, just my headphones. the line out to the poweramp didnt contain any of the headphone mix as i sent it from the effects send (which is post eq on swr. worked great, i finally was able to hear myself in a room with a loud drummer. BTW, this should be able to work with any amp that has a blendable effects loop and a headphone out.