Kitís Secret Guitar, Gear, and Music Page
B.K. BUTLER TUBE DRIVER
©Kit Rae. Article written in 2007. Updated in 2010, 2011, 2013, 2015, 2016
B.K. BUTLER REAL TUBE OVERDRIVE - 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 master volume, HI (treble), LO (bass), and drive control. The 5 knob version adds a MID knob. Inside is a hybrid fuzz - pre amp circuit. The hard 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 as it would in the pre amp stage of a typical amplifier. It filters and colors the sound with the tube characteristics. 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 different tubes to tailor their tone.
I think the TD sounds best with clean amps, like the Hiwatt Custom 50 or Custom 100 (DR103), or similar amps like the Reeves Custom 50/100. It also sounds excellent with certain Fender amps, particularly the Fender Bassman, or it's high powered step brother, the Marshall JTM-45. The four knob Tube Driver sounds best with amps that have a moderate mid range, like a Hiwatt. For mid-scooped amps, like the Fender Twin Reverb, the Real Tube version with the mids knob is better. Some amps that do not have a lot of head room and break into distortion at high volume do not play well with it. It also does not sound good when certain pedals are before or after it in the signal chain dues to the high impedance output. Unlike typical effect pedals, the Tube Driver includes a built in power cord, as it uses an internal transformer, which can be noisy for certain users.
TUBE DRIVER VERSIONS - There have been numerous version of the Tube Driver made since the 1980s, but these are all of the 4 knob versions. A mostly complete list of all the other versions can be forund HERE.
•1985 - B.K. Butler/Chandler Tube Driver. Marked TUBE DRIVER™ and CHANDLER INDUSTRIES-PATENT PEND. on the front.
•1986 - B.K. Butler/Chandler Tube Driver. Marked TUBE DRIVER®, Concept & Design: B.K. Butler and CHANDLER INDUSTRIES, INC on the front.
•1988 - Chandler Tube Driver. Knockoff made by Chandler after Butler parted ways with them. Only marked with script Chandler logo on the front, no BK Butler.
•1993-94 - 911 Tube Driver - Made by Butler's Tube Works company. A four knob version of the Tube Works 901 Real Tube pedal, which was an improved Tube Driver.
•2005 - 911 Tube Driver. A reissue of the 1990s Tube Works Tube Driver.
I have owned several versions of Butler's Tube Driver, including a few original Chandler/BKB versions from the 1980s, a 1989 Real Tube with 5 knobs, a 911 model, a few 911 reissues with the bias knob, a 1996 Ibanez Tube King, and a Tube Works Smooth pick pedal, among others. I have played most of the other variants as well and I suggest staying away from any but the original 4-knob Tube Drivers branded with both BKB and Chandler, Tube Works branded 911 Tube Drivers made in the USA, the USA made Ibanez Tube King, or the BKB Branded 911 Tube Drivers made since 2006. The three knob version and other Taiwan made versions may be found for much less money, but they do not sound the same. I do not recommend the knockoff Chandler version with the attached wall wart either (the one without BK Butler's name on it), as those have a different tone circuit that sounds like a poor imitation of the BKB circuit.
Various versions of the B.K. Butler Tube Driver Circuit.
There are basically two different circuit boards used in the original BKB/Chandler 1986-87 Tube Drivers. The first one had a light green-tan colored pcb with the trace and resistors on one side, everything else on the other. The trace side is marked 9 3151•Z. I have seen two slightly different sets of component values on that board, and in my experience and based on what other owners have said, no two sound the same. I currently own two and have played four side-by-side. Two of them sounded identical to each other (and identical to the second version mentioned below) and the other two sounded very different. Those two required the drive pot to be above notch 3 to get any sound.
Butler had a firm in California manufacture a second circuit board for him sometime in 1987. The trace side was dark green on this version. Most components were soldered on the front side, but a few caps and resistors were on the trace side. It had no identifying numbers or letters, and I have seen two slightly different sets of component values on this pcb. I have owned several of this version and each sounds nearly identical. David Gilmour used two 1986-87 era Tube Drivers in his massive Pink Floyd rig in 1994.
In 1987 Butler made made an improved version called the Real Tube through his Tube Works company. It added a mids knob, allowing a strong mid boost to be dialed in, getting into the Tube Screamer territory. It had a much wider tone range than the earlier 4 knob versions. With the mids knob dialed almost off, the tone range is basically the same as the 911 version Butler made in the 1990s, and the 911 reissue he began making in 2005. The 5 knob Blue Tube Enhancer (model 903) and Smooth pick pedal (model 303) are lower gain versions of the same circuit, suitable for mid gain overdrive and rhythm playing, or boosting an amp or high gain pedal.
Around 1993 Butler made a new version of the older 4 knob Tube Driver through his Tube Works company, called model 911. It was basically the Real Tube circuit without the mid range knob, not the older BKB/Chandler circuit from the 1980s. The circuit layout and pathways were very similar to the 1980s circuits, but there were several component value changes across the circuit that affect the way it sounds. Butler sold the Tube Works company in the 1990s and they were later shut down. In 2006 Butler reissued the 911 Tube Driver by custom order through his Butler Audio company. This version was used by many popular guitarists, including David Gilmour, who used in his 2006 On an Island pedal board and 2015/16 Rattle That Lock pedal board.
In 2008 Butler added a bias knob as an option. That was a feature I found made little difference to the sound, but some people find it useful. 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. The full + setting is the same as the non bias version, but I found that rather than softening the distortion with the bias reduced, it tended to make the sound die faster. I found it more effective to simply change the tube, but others really like this feature.
B. K. Butler
B.K. Butler still makes 911 Tube Drivers by hand (at the time this article was written) through his Butler Audio company, HERE. Used models are also plentiful and easy to find online. If you want to read more about B.K. Butler and the Tube Driver, there is a good interview over on the fantastic Tone From Heaven website. A list of most of the Tube Driver versions can be found HERE.
SOUND CLIPS - These are almost all Pink Floyd/David Gilmour inspired tone clips. With just a light drive setting the TD works great with a neck pickup for solos and blues playing. It is perfect for songs like Shine on You Crazy Diamond and Coming Back to Life. The sound holds its own against a Big Muff when cranked into full overdrive. Here are clips of different Tube Drivers played with a Stratocaster fitted with EMG-SA pickups through a Fender Twin Reverb and a Reeves Custom 50 (Hiwatt Custom 50 replica), and a P-90 Les Paul into a Reeves or Fender Bassman.
Coming Back to Life solos - Boss CS-2 compressor >1980s BKB/Chandler Tube Driver > Boss CE-2 chorus > TC Nova delay. First solo with EMG-SA neck+middle pickup. Second with neck pickup. Reeves Custom 50.
Clips below are played with a 2008 American Standard Strat, Seymour Duncan SSL-5 bridge pickup, Fender CS69 neck pickup, or Seymour Duncan SSL-5 bridge pickup, into a '65 Fender Twin Reverb RI or a Reeves Custom 50.
LIGHT DRIVE / BOOST SETTING - Example of the Tube Driver light drive setting with a Fender Strat into a Reeves custom 50. Settings shown above.
CAN A TUBE DRIVER HANDLE LEADS LIKE A BIG MUFF? - It can, and Gilmour has been using the Tube Driver as his main distortion since the 2006 On an Island tour finished (according to him and his backline tech), and his TD overdrive settings from the same tour produced a very muffish distortion. It does a great lead tone, although it does not have quite the same huge bottom end and scooped mid range you find in a Ram's Head era Big Muff. I was going for the Pulse era live tone here. A Civil War Big Muff was used for the song Sorrow, so I'm using the Tube Driver here to compare to a Muff. Strat into a Fender Twin Reverb.
BOOSTING A BIG MUFF WITH A TUBE DRIVER - A Tube Driver can be used as a light boost before or after a Big Muff in the signal chain. Muffs like to be driven hard and like a loud, clean tube amp to sound good, but sometimes that is not enough for lead or solos, especially with modern Muffs. By 'boost' I don't mean a volume boost, but more of a blend of the two pedals. Driving a Muff with a driver can make the Muff tone come alive, smooth out the tone while adding some gain and mids, and help it cut through in a band mix better. Most modern Muffs and some vintage Muffs can really benefit from this type of boost. The Big Muff sound is slightly warmer when placing before a Tube Driver, and slightly sharper when placing it after. The tone of a Tube Driver is fairly transparent when using as a boost, but you can also lightly color the Muff tone when boosting.
BIG MUFF BOOST (settings shown above)
Tube Driver set for boost AFTER a Civil War Big Muff - smooth tone
Tube Driver set for boost BEFORE a Civil War Big Muff - grittier tone
OLD 1986-87 ERA B.K. BUTLER/CHANDLER TUBE DRIVER VS 2000s ERA B.K. BUTLER TUBE DRIVER - The core circuit design on the 2000s reissue 911 Tube Driver is similar to the original 1985-87 versions, but there were several component value changes across the circuit that affect the way it sounds, as well as different pots. Do they sound different from each other? Tube Drivers of different eras can sound slightly different from each other anyway, primarily because of differences in the way different tubes filter the sound, but also because of how the circuits were slightly revised over the years, and how the components have aged. There was a 1986-87 circuit (with two variations), a 1987 circuit (with two variations), a model 911 circuit board from the 1990s, and a reissue of the 911 that Butler started making around 2005. Each requires different settings to sound the same. However, when using the exact same tube, each can be dialed to sound nearly identical, with the exception of some of the 1986-87 models. If we look at the more common circuits from 1987, the LEVEL, HI, LO, and DRIVE knobs need to be set very differently to get the same tone on a 911 or 911 reissue Tube Driver. The photos below illustrate the differences using a 1987 Tube Driver and a 2007 reissue model 911 Tube Driver.
Light drive settings for the common 1987 BKB/Chandler Tube Driver and settings to match the same tone on a 2007 model 911 Tube Driver
Overdrive settings for the common 1987 BKB/Chandler Tube Driver and settings to match the same tone on a 2007 model 911 Tube Driver
The primary difference is much more low end available in the 2007 version than the 1987 version, so it can be dialed into much heavier, fatter tones. There is slightly more drive/gain available on the 2007 TD when set to 10 than most of the 1980s TDs. The 2007 TD offers drive/gain all the way from 1-10, whereas on most of the the older TDs there is no volume at all until the drive gets up to around 2. The 2007 TD also has "notched" pots, like the Tube Works versions, meaning you feel tiny notches click by as you turn the knobs. Notches 1-2 do little on the 2007 TD drive knob, then at notch three there is a huge jump in volume and drive.
Below are a few comparison clips. These clips are not the correct overdrive settings for Shine On You Crazy Diamond, just what I had set at the time I banged them out. The drive is set around 85%. Both TDs use the same GE brand 12AX7 tube. Strat into a fender Twin Reverb.
Shown Above - The original 1986-87 BKB/Chandler Tube Driver circuit with components on both sides. These can sound wildy different from unit to unit.
Shown Above - The second version of the BKB/Chandler Tube Driver circuit from 1987 with most components on the front side
Shown Above - The simplified, cheap, and poor sounding Chandler Tube Driver circuit
Shown Above - A 1994 Tube Works model 911 Tube Driver
Shown Above - A 2007 BK Butler Tube Driver circuit with bias knob, which was a reissue of the 911 Tube Works Tube Driver, not the 1980's Tube Driver
REAL TUBE by TUBE WORKS - Other than one being in super cool enclosure, and the other in a butt-ugly enclosure, the 4 knob 911 Tube Drivers and 5 knob Real Tube versions are basically the same patented B.K. Butler designed Tube Driver circuit with some component differences. The Real Tube includes a mid range knob, allowing for a wider range of tones to be dialed in. In that way, it is actually a superior pedal to the 911 Tube Driver, and housed in a smaller enclosure. It is powered by an internal transformer and includes a power cord like the Tube Driver. There was a USA made version by Tube Works beginning in 1987, and a Taiwan version made when Tube Works was sold to Genz Benz in the 1990s. The only real difference between the two was less expensive, cheaper parts in the Taiwan version. Some of those Taiwan pedals were made with a 9v or 12v DC power jack on the back, rather than a built in power transformer and AC cord on the earlier models.
IBANEZ TUBE KING TK999US - This is another B.K Butler design, made by his Tube Works company for Ibanez. It is basically the 5 knob Real Tube circuit with a few changes and improvements, like an active tone circuit rather than the passive circuit in the Real Tube. Unlike the 911 Tube Driver and Real Tube, the Tube King includes an output buffer so it is immune to most capacitance and loading issues that can plague those other pedals. It also runs off a standard 9v DC power jack, not an internal transformer, so noise issues associated with the internal transformer in the Tube Driver and Real Tube have been eliminated. When using the same tube, it can sound 90% the same as the Real Tube or 911 Tube Driver. The pcb includes the Butler patent number 5022305. Note: there were two versions, one from Tube Works that was made in the USA, and one made in Japan by Maxon for Ibanez and Maxon branded versions that were sold internationally. The Japanese version does not follow Butler's circuit.
4 KNOB 911 TUBE DRIVER vs 5 KNOB REAL TUBE - Other than the mid range knob, do the Real Tube and 4 knob 911 Tube Drivers from the 1990s and 2000s sound any different? Tube Drivers can sound slightly different from each other anyway, primarily because of differences in the way different tubes filter the sound and circuit variations, but when using the exact same tube, the 911 and 5 knob Real Tube versions can both dial in nearly identical tones. The US made version of the 5 knob Ibanez Tube King is also based on the Real Tube circuit and sounds very similar.
The photos above show what the Real Tube and Tube King settings need to be to match the tone and drive of the 2007 reissue 911 Tube Driver settings on the right
Even when using the exact same tube, the same knob settings on the Real Tube and Tube King will NOT result in a matching tone and drive on the 4 knob 911 Tube Drivers built after 2005. To get the Real Tube and Tube King mid range to match the pre set mid EQ in the 911 Tube Driver you have to dial the MID knob down to around 9:00. The highs and lows on the Real Tube and Tube King are also notched a bit differently than the 911. The photos above show what the Real Tube and Tube King settings need to be to match the tone and drive of the 911 Tube Driver settings on the right.
Shown above - J Mascis 5 knob Tube Works Real Tube Overdrives with J's settings, and his four knob 911 Tube Driver.
Shown above - Joe Bonamassa's preferred Tube Driver is the Genz Benz 911 version from the 1990s, shown above
Shown above - Joe Bonamassa's pedal board with a 2006 era 911 Tube Driver
911 TUBE DRIVER REISSUE MANUAL
REPLACEMENT TUBE DRIVER KNOBS - The yellow capped knobs used on the reissue 911 Tube Drivers made since 2005 are unique to B.K. Butler, as he owns the tooling. You can't find those exact knobs unless you buy them direct from him. The various versions of the yellow capped knobs used on the older Tube Drivers were cheaply made and broke easily, and the the yellow caps were prone to falling off and becoming lost. It is very difficult to find these same knobs now. Below is a comparison of the different knobs used, and a modern RS Knobs replacement.
RS Components makes a very similar grub screw knob with separate caps, shown below, but it is slightly taller and wider than the TD knobs. www.alliedelec.com also sells the same RS knob and caps. The caps come in several colors, including red, for those of you that want the cool look of David Gilmour's #1 Pulse Tube Driver. They don't exactly fit the older Tube Driver knobs or the smaller knobs used on the 2000s Tube Drivers, but can be modified to fit.
Rapid Electronocs sells more accurate knob and caps, but slightly larger than the TD knobs. They are made by Sifam in the UK. They are D shaft knobs, so they would need to be drilled out to make round. Sifam discontinued the round shaft hole version, the TPN150, which I believe was nearly identical to the original Tube Driver knobs.
Knobs: Sifam DCN150
Caps: Sifam C151
MODIFICATIONS - Changing Tubes - This is the simplest, most effective mod for a Tube Driver. Some people find the distortion too rough sounding, even and low drive settings, and want a smoother, cleaner sound. Since the distortion is generated by the op-amp, not the tube, it would seem changing the tube would have little effect on the level of distortion. A lower gain tube will not necessarily reduce the amount of distortion, but it can smooth and tame it at medium to low drive levels. What it does is color the distortion. Here is what the original Tube Driver Users Guide said about the tubes:
In typical power amplifiers the preamp tubes can easily last 15 years or more with moderate use and 10 years or more with very heavy use. Since the Tube Driver is a starved plate design, the tube will last much longer (even though the original user guide said they only lasted 2-4 years!). Chances are you will never have to replace it, but you may want to experiment with different tubes to see which sounds best in the TD to you. The tube is usuallu glued to the socket with a rubber silicon, but you can peel or cut that away. The stock tube shipped with Tube Drivers was alwasy a 12AX7, but different brands of tubes or tube types may alter the sound in different ways. Some people don't really hear any difference when swapping tubes, and others hear drastic differences. In my experience, the differences are more noticeable at high volume, and at high drive settings on the TD.
Shown above (left to right) - An original long-plate Ei Yugoslavian 12AX7 tube re-branded "TUBE DRIVER" that shipped with the original BKB/Chandler Tube Driver in 1986-87, the same tube branded "CHANDLER ELECTRONICS" that shipped with some 1987 Tube Drivers and the cheap Chandler branded Tube Drivers in 1988-89, and a short plate, unbranded Goldern Dragon 12AX7 that ships with the reissue Tube Drivers made since 2006.
Original BKB/Chandler branded Tube Drivers from 1986-87, and the cheap Chandler version from 1988-89, shipped with a long plate Yugoslavian Ei 12AX7 tube with custom branding. There was also a version branded Real Tube that shipped with the Tube Works 911 Tube Drivers in the 1990s and some early 911 reissues in 2006. Butler called the 1970 'NOS' YUGO tubes, meaning "new old stock" tubes made in Yugoslavia in the 1970s. He ran out of them in 2006.
The stock tube that ships with the 911 Tube Driver made since 2006 is a Golden Dragon 12AX7 - a low noise, hi-fi preamp tube. It is unmarked, other than BK written on it with a Sharpie. It created a bit too much distortion for the low drive settings of the TD for my taste, so I swapped tubes to a lower gain 12AU7. Lower gain should give a smoother sounding overdrive, but that's not always the case with different tube brands. The 12AU7 did not really reduce the gain from the drive pot, but made the distortion less fuzzy sounding so the individual strings in a chord had more clarity.
Very few factories make vacuum tubes the way they used to be made these days, so it is worth noting that certain NOS (new old stock) tubes can sound much better than most modern tubes. I suggest staying away from cheap, noisy tubes, such as the Groove Tube brand. The best modern tubes seem to be the ones made by JJ Electonics. I have tried various tubes, including an old GE 12AU7, Ei Yugoslavian 12AX7, and JJ Electronics ECC83/12AX7 in my current TD's. The 12AU7, being a slightly lower gain tube than the 12AX7, was slightly smoother and cleaner sounding at low drive settings in my BKB/Chandler TD, but there was a less noticable difference in my 911 Tube Drivers. I tried 12AT7s in the 911 and did not hear a big difference vs the 12AX7. I have a cheap Electro-Harmonix 12AU7 in my 5 knob Real Tube that sounds as nice as the NOS tubes in my 911 TDs, so even a cheap tube can sound good.
Below are the tube gain factors if you want to try for a heavier or cleaner sound than the stock 12AX7.
MODIFICATIONS - Changing op-Amps - As stated, most of the hard clipping distortion comes from the op-amp, not the tube. You may notice that the op-amp on the circuit board is mounted in a socket in the modern BKB Tube Driver, so you can swap out other higher quality op-amps to see if you like the sound better. The op-amp is the small black boxed IC chip with 8 pins on the left hand side of the circuit in the photos below. You can pull it out by hand and replace it with any other 8 pin dual op-amp chip. I tried a JRC4558D (used in the older TD), and another that I think was an OP275. Those did not improve or change the sound to my ears at all, but I did have good results using Burr Brown OPA2134 op-amps. It was noticably smoother at low gain and I liked it better than the stock TL072 chip that shipped with my 911 TD in 2007. It only made a minor difference however. In a blind test, most people would find it difficult to hear much difference.
MODIFICATIONS - Remove the Internal Power Supply to Reduce Hum - To avoid the noise issues caused by the internal transformer being so close to the audio circuit (described in the KNOWN ISSUES section below), the transformer can be moved outside of the TD enclosure. This can be done by removing it, enclosing it in a protective plastic enclosure, and running longer lead wires back to the Tube Driver. This is exaclty what Chandler did with their copy of the Tube Driver in 1988. This is what their Owners Manual said: By locating the transformer outside of the box we have been able to accomplish three objectives: Noise and hum is significantly reduced. Shock hzard has is practically eliminated. The Tube Driver now conforms to international UL standards.
You can also remove the transformer and add an AC power supply jack on the back of the enclosure, so it can be powered by 12vAC (not DC) external power supply. The power supply needs to run at least 12.6vAC at 200mA-500mA. First disconnect the existing internal transformer that is riveted or screwed to the front end of the enclosure. Note which leads from the transformer run to the circuit board. Drill a hole and install a 1/8" power jack on the back of the enclosure. The polarity of the jack does not matter like it does on a standard pedal running DC, since the Tube Driver runs off AC. Solder the leads from the 1/8" jack back to the circuit board. Plug the external AC power supply in and you are ready to go.
It is also possible to convert the Tube Driver to DC power so it can run from a standard pedal power supply, as is the case with the Tube King and some Taiwan made Real Tube pedals. It is more complicated however, and requires running the leads from the DC power jack before the filtering section and after the rectifier section of the circuit. It is best to have an electronics tech do that unless you have some experience with this sort of thing.
KNOWN ISSUES - Below are some of the well known quirks with this pedal that may cause problems for people with certain setups, and some ideas for how to correct them or deal with them in your signal chain.