I have a Roscoe/Demeter preamp for trade. Do you want to tighten up the lows and add some sweet glassy highs to your Roscoe? Want a more modern tone? This is the preamp you want! This is the 4 Knob version with the Q-switch and can operate on the following volts DC, 9vdc, 18vdc or 27vdc. That's right, if you have room for 3-9volt batteries you will have headroom galore! I am doing a little experimenting and need a Aguilar OBP3 in the 4 Knob configuration with preferably separate switches for the mid and active/passive controls. I would also consider a 4 knob U-Retro with the 2 switches.