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The Tube Driver is a booster/overdrive pedal with an IC and vacuum tube-driven preamp circuit inside, used by guitarists such as David Gilmour of Pink Floyd, Eric Johnson, Billy Gibbons, Joe Bonamassa, Joe Satriani, Kenny Wayne Shepherd, J Mascis, David Holt, Keith Urban, and others. It was designed and built by audio electronics engineer B.K. Butler (Brent Butler). Around 1978 Butler designed and began making an early version of the Tube Driver, one of the first tube overdrive pedals. It has evolved over the years and there are many versions (a list can be found HERE). It generates anything from a smooth, light overdrive tone, to a classic rock-style heavy distortion. At high gain, it is very reminiscent of the lead crunch tone of a Marshall JCM800 amplifier. At low drive it can deliver a Fenderish smooth gain boost or a bluesy overdrive. It is not very versatile sounding through some amps, but exceptionally good with others. It can be difficult dial in a tone setting that hits the sweet spot, and some people find it finicky and hard to get along with due to some design issues, but 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.
The Tube Driver looks like something from the bridge of the Enterprise from the 1960s Star Trek television show. The standard 4 knob version features a LEVEL (volume control), HI (treble), LO (bass), and DRIVE control. The 5 knob version adds a MID knob. Inside is a hybrid fuzz - preamp circuit. The clipping part of the distortion comes from the integrated circuit chip, or op-amp. That strong signal is fed into a vaccuum tube, which does not work to amplify the signal the same as it would in the preamp stage of a typical amplifier. It filters and colors the sound with the tube characteristics. The circuit only draws about 30mA and the tube is actually only running at 12v, a fraction of what these tubes run in a typical amplifier. This is called a "starved plate" design, and you won't see much tube glow, if any, if you look inside. It would seem that the tube itself would make very little difference to the sound, but it actually is an integral part of the sound, and different tubes or tube types will alter the sound in different ways. Butler has always made these stock with 12AX7 tubes, but owners typically experiment with tubes having different gain factors to tailor their tone.
The Tube Driver was one of the first tube overdrives to enter the effects pedal market in the late 1970s. It became a very popular pedal among guitarists for the next 35 years, and onwards. Inspired by the Hammond organ sound of the band Deep Purple in the 1970s, the genesis of the Tube Driver happened when Brent K. Butler wanted to overdrive his keyboard by modifying the tube amplification circuit of an old stereo record player. He mounted the circuit in a Radio Shack enclosure and let a few local guitarists try it out. The positive response led Butler to further reduce and simplify the circuit, making an early version of his Tube Driver pedal for friends around 1975.
After getting some practical work experience in electronics working for Carvin amplification, Butler refined the Tube Driver even more. He first marketed and sold them publicly in 1979, under the Butronics brand. They were housed in a blue metal box with 3 knobs and a 6AV6 or 12AV6 tube inside. He then made a 5-knob version called the Mini Boogee in 1980, sold through his Audio Matrix business that he ran out of Carvin's old building. He later changed the name to Mini Matrix after getting a cease and desist from Mesa Engineering, who owned the name Mesa Boogie. The Mini Boogee/Mini Matrix circuit included two 12AX7 preamp tubes. Butler then reworked the design again, combining an op-amp (operational amplifier or integrated circuit chip) and a preamp tube running on starved voltage to generate the distortion, which led to the popular 4 knob Tube Driver. Butler says he designed that version in 1983 and it was produced in 1985.
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