COLORSOUND OVERDRIVER - A reissue of the old classic 1971 Colorsound Overdriver, still distributed by Macari's of London, and hand made by Jake Rothman/Theremin.co.uk at the time I write this (2007). The Overdriver is a bass and treble boost/overdrive pedal that works great with tube amps. It sounds almost like a little amp in a box, and it is LOUD. David Gilmour of Pink Floyd used the old orange Power Boost version throughout the 1970's on such tracks as Shine On You Crazy Diamond, Have A Cigar, Pigs and many other mid to late late 1970s Pink Floyd songs. He also used it on the 1977 Pink Floyd tour for that incredible Power Boosted Big Muff sound, and used the Overdriver version in the 1990's. Jan Akkerman of Focus was another heavy user of this pedal, as were Marc Bolan of T Rex and Jeff Beck. The Overdriver is a piece of british fuzz history.
The Overdriver circuit is almost identical to the original 18v Colorsound Power Boost released circa 1969-70, but includes a master volume knob, and a bit more gain when the drive is set to maximum on the example I own. There were three slightly different schematics for the PB/Overdriver, so some vinatage units will sound slightly different from others. The Overdriver gives a very transparent and super clean boost that sounds very dynamic and open. The bass and treble controls give a wide range of tonal options, including a full-on treble boost, and overall it has a very unique overdrive sound that you won't find in many modern drive pedals.
It can make any tube amp have a more hi-fi sound just using the clean setting. The drive control really does not do much, but when you get to the 90%-100% setting, the doors open wide. A very nice vintage Fuzz Face type overdrive blasts in. Nothing quite like it. Great for vintage '70s rock. With the Overdriver plugged into your amp, the tone gets better the more you crank up the amp volume. This pedal will improve your tube amp tone.

2007 Colorsound Power Boost and Overdriver reissues
Placing a Fuzz Face or Big Muff type pedal before the Colorsound Overdriver, set for a light overdrive, creates a really nice vintage 1970's David Gilmour fuzz tone, especially through a Hiwatt amp like the Custom 50 or Custom 100. I use the Overdriver for much of the light overdrive tones and some fuzz tones for Dark Side of the Moon and Wish You Were Here, and as a light boost after my fuzz pedals like the Analogman Sunface BC108 Silicon fuzz. I have also found the Overdriver placed after the Big Muff is the only way to recreate the distortion tones David Gilmour used during the 1977 Animals/In the Flesh tour, and on the 1978 Columbia Records promotional videos David made for his first solo record, and possibly used on the record itself. The dry treble and fuzz from the Colorsound is very distinct when used with the Big Muff in this way. I also leave the pedal on all the time with a very light drive setting, a trick I learned from Gilmourish.com. It really makes my tube amps sound better.
Gilmour used several other overdrive pedals throughout the years, with the BK Butler Tube Driver being on of his favorites, but nothing has quite that same early Pink Floyd overdrive tone like the Power Boost/Overdriver. You can also find less expensive clones like the Throbak Overdrive Boost. A Boss BD-2 Blues Driver will work for this, but it is not quite the same sound.
The Colorsound only runs on 9v batteries (though an AC adaptor version is coming), and sounds best with non alkaline type. The only real drawback to the Overdriver, other than the high cost, is that even with the master volume set to zero, the minimum volume level is higher than unity when the drive knob is set for maximum overdrive. The circuit does not allow the volume to go to zero. This makes it almost impossible to use on a modern pedal board with other pedals at unity volume, because with any high drive level, the Overdriver will almost always be too loud. Placing the pedal in a bypass loop with another pedal used as a volume reducer is one way to overcome this, but there is also a simple mod that allows the volume level to be lowered (See below). The Overdriver is housed the the classic pressed metal Colorsound case (22cm x 9.6cm), with a nice vintage hammerite finish. The bottom of the case pops off for access to the battery.
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Vintage 1970 Power Boost ad, original 1970 Power Boost, 1971 Overdriver, 1975 Overdriver in wide box, and late 70s Overdriver with white label.
The original 18v Colorsound Power Boost was released circa 1969-70 as one of the first Macari's/Sola Sound pedals in their new Colorsound line, sold by Macaris Musical Exchange in London. The Power Boost ads I have come across appeared in 1970. This 18v treble and bass booster-drive boost pedal was encased in a bright orange enclosure which did not go over too well in the US, so it was repackaged in a gray enclosure, changed to 9v power, and renamed the Overdriver, circa 1971 (factory schematic dates 14.6.71). There was also a version made for Vox in a different enclosure (Tone Bender Mark III case) around this time, in the same gray color, but using the Power Boost name. The circuit was possibly designed by Gary Hurst, creator of the Sola Sound Tone Benders, and many other Sola Sound/Colorsound circuits. Gary mentioned he was working on a new foot pedal with a bass and treble boost back in the January 1966 issue of Beat Instrumental, when British booster units were very popular. It was described as being a volume pedal. Gary did design a bass and treble booster housed in a volume pedal case for CBS/Arbiter, called the Power Driver, though that was much later in 1974 or 1975. The Power Boost and Overdriver were made in the original thin Tone Bender pressed sheet metal cases, then rehoused in the wide body Supa Tone Bender style case in the mid 1970's, with a white label added to the top in the late 1970's. Several improvements were made to the circuit throughout the years. Around 1996, legendary Vox engineer Dick Denney worked with Macaris on the reissue Overdriver, the last pcb he worked on before he died. The reissue incorporated a much needed volume knob into the design, which was also added to the Power Boost version. In 2008 Jake Rothman revised the Overdriver circuit to add a FET buffer at the input, improving your guitars tone control interaction with the circuit, and the same was done to the Power Boost in 2004. Other revisions have been made, including changing the drive pot to anti-log, giving a wider gain spread, and adding an AC adaptor jack and power LED. (thanks to Philip and Jake for additional info)
OVERDRIVER MINUMUM VOLUME MOD - If you desire the volume pot on your Overdriver to go to zero instead of the mimunum volume, you can do this simple mod. Remove the 82ohm resistor (circled in red in the photo below) coming off the ground pin of the volume pot. Run the wire straight from that pin to the board, without the resistor. You can also remove the 10uF electrolytic capacitor under the volume pot for reduce the gain by 6db, but note that it will also reduce the trademark clipping spike when the drive is set to maximum. (Big thanks to Jake Rothman for the mod).
OVERDRIVER REDUCED GAIN MOD - If you do not like the trademark clipping spike when the drive is set to maximum fuzz (though who would not like this?) and desire the gain to be reduced slightly for more of an overdrive sound, you can remove the 10uF electrolytic capacitor under the volume pot and run a wire in its place. This will reduce the gain by 6db. (Big thanks to Jake Rothman for the mods).
Soundclips of David Gilmour using the Colorsound Power Boost
Gilmour Power Boost Sound Clips - Examples taken from the Shine on You Crazy Diamond studio track, April 1975 concert, June 1975 concert, 1977(?) concert, July 1977 concert (last show), and then non Colorsound examples from DSOT live CD, Pulse live CD, Remember That Night live DVD, and the Live in Gdansk CD, in that order.
SOUNDCLIPS - Clips below are played with a 2008 American Standard Strat, Fender CS69 neck pickup and SSL-5 bridge pickup, into a '65 Fender Twin Reverb RI.

Colorsound Overdriver Rhythm Demo - Pigs
Three clips of the rhythm part from Pigs. First is a mild boost, then heavy boost, then full overdrive.
Pigs rhythm part with artificial double tracking to simulate the sound heard on the Pigs studio track.

Colorsound Overdriver Demo - Shine On You Crazy Diamond
Three clips with an overdrive setting - first is the Colorsound only, second is the Colorsound with a Boss CS-2 compressor added, and third is the Colorsound with MXR Dynacomp compressor added.
Colorsound Overdriver Demo - On An Island
Trying a modern Gilmour overdrive tone with the first On An Island solo.
Colorsound Overdriver Demo - Overdriving a Ram's Head Big Muff
Just messing around making horrible noise overdriving my Ram's Head.
MORE SOUND CLIPS - Fender strat with SSL-5 bridge pickup into Overdriver, MXR Carbon Copy analog delay, and Fender Twin Reverb.
Colorsound Overdriver Sound Clip 1 - Colorsound on light boost playing Money bass line.
Colorsound Overdriver Sound Clip 2 - Colosound on light overdrive playing Time solo.
Colorsound Overdriver Sound Clip 3 - Colorsound on maximum overdrive playing Time solo.
NOTE - I have listed the gear and settings I use in most cases, for reference, but note that the tones may not exactly match your rig, depending on which amp you use, your guitar, and pickups, and fingers :) I am not a Gilmour/Pink Floyd gear expert, so your results may vary.
Article written in 2007. Updated 2011