Tube Works "Blue Tube" designed by BK Butler #RT-904. You can use this as a in line or side-chain effect OR it makes a great preamp with a killer on board over drive. I have used it both ways and it works perfectly. I replaced the AX7 tube with a vintage (1959) RCA AU7 witch gives the overdrive a much warmer overdrive. Both tubes will come with this unit. Some of the pots are a bit scratchy in places but not overwhelmingly so. It also has a great Boost switch that is foot switchable as well as the bypass (foot switch not included) Unit has minor rack rash, see pics, nothing to be concerned with. PRICE DROP $125.00 shipped conus No trades at this time.