I usually play the synthesizer and guitar but I don't want to haul the keyboard and guitar amps together. Most of the time I just hook up a pre-amp in between my guitar and the keyboard amp, but I would use no effects and that sounds pretty dull. I finally went out and got myself the TwinTube (SFX-03) this afternoon and tried it out on my Roland keyboard amp. I could tell the difference as soon as I played my first note. It enhances the sound of the guitar but it retains the characteristics of the the guitar and the amp. I was using my Strat with the Cool and Hot Rails and they sounded very good either in series or split and I could get a lot of different tones from the SFX-03; from clean Jazz to full shred and everything in between. I don't have a chance to try it out on my other amps yet, which have effects and EQs and guitars with different pickups because I have to leave my house. I can't wait to find out how they will sound.