Here is a rare BK Butler designed Tube Works Bass Driver. This is one of the premier drive units available for bass guitarists. I even like it on guitar. This is in great condition, and sounds excellent. It has a milder 12AU7/ECC82 tube installed, I will include a 12AX7 tube. $110 shipped, Paypal I ship to the 48 states only. Please message me with any questions. Thanks!