This is the Bias adjustment capable version.

BK BUTLER REAL TUBE OVERDRIVE - The Tube Driver is a booster/overdrive pedal with a simple vacuum tube driven preamp circuit inside, used by David Gilmour of Pink Floyd, Eric Johnson, Billy Gibbons, Joe Satriani, and other top guitarists. It was designed and built by B.K. Butler. Mr. Butler is primarily a home and car audio premap specialist. Around 1978 he desgned and began making an early version of the Tube Driver, one of the first tube overdrive pedals. It has evolved over the years into this current version. It generates a smooth light drive/boost tone and a killer heavy overdrive. in the right setup, with the right amp, nothing sounds quite like it. The TD has a very unique voice that I have never heard another overdrive replicate. It features a master volume, hi (treble), Lo (bass), and drive controls, allowing for a wide variety of tone colors.

I t for that Pulse and On an Island era David Gilmour light drive tone with a Hiwatt or Reeves amp, this is your pedal. It replaced the Colorsound Power Boost David used in the 1970s and Pete Cornish ST-2 Booster (Power Boost clone) from the late 1970s, and remains his primary overdrive. You can hear this pedal's light drive tone in songs like Coming Back to Life, Marooned, A Great Day for Freedom, and the live versions of Shine on You Crazy Diamond from Pulse. It was also used to boost/color David's Big Muffs for the Division Bell and On an Island tours.

David used two BK Butler/Chandler Tube Drivers in his 1990s Division Bell live rig, shown above. One was used for a clean drive/boost tone and the other as a drive booster for his Big Muff. Gilmour's 2006 On an Island board used two new B.K. Butler hand made Tube Drivers. These were a slightly different version to the original BK Butler/Chandler version. One was set for overdrive, and one was set for a light boost to drive the Big Muffs a bit harder, and for use alone as a light drive pedal as he had done in the 1990s. The Tube Driver settings can be seen in the photo above set for a light drive boost.

There are many other versions of the Tube Driver that have been made, most under the Tube Works, one under the BK Butler/Chandler brand, and an unauthorized knockoff released be Chandler after Butler parted ways with them. There is also a rack mount version. I have played most of them and I suggest staying away from any but the two mentioned above. The three knob version may be found for much less money, but they do not sound the same. I do not recommend the Chandler version without BK Butler's name on it. I have a 2007 model hand made by BK Butler and an original Chandler/BKB version from the 1990s on my board. The 2007 version is 'Real Tube Overdrive' model 911, the same as what David Gilmour used in his 2006 On an Island pedal board. The BK Butler/Chandler Tube Drivers are very similar. The TD comes stock with a 12AX7 tube. The bias knob allows you to reduce the gain, similar to what would be accomplished by changing to a lower gain tube like the 12AU7. I found it more effective to simply change the tube. A 12AU7 tube is lower gain can remove some of the sharpness from the tone at low drive settings.