A treble booster is an effects unit used by guitarists to alter the sound of their guitars.
Popularized by guitarists such as Tony Iommi, Ritchie Blackmore, Rory Gallagher, Brian May, Marc Bolan and Andy Scott, treble boosters have been used to overdrive amplifiers (mostly dark sounding, British tube models such as Marshall Bluesbreakers and Vox AC30s) in order to create a more distorted yet focused sound. They came up in the mid-1960s. By the 1980s they had become obsolete. Guitarists used overdrive pedals instead, in a similar fashion. In recent years treble boosters have gained some popularity again.
Players sometimes prefer using a treble booster with a tube amplifier that is already moderately overdriven. Treble boosters typically cut some low end and amplify the signal, thus creating a "tighter" sound with more treble or high midrange emphasis.
There have been several different types of treble boosters made.
One of the most important early examples is the Dallas Rangemaster, which was widely used in the late 1960s and early 1970s. Hard to find today, the Rangemaster sound is still sought after, and many clones based on its extremely simple circuit have been made commercially and by hobbyists. Unlike most of today's clones, the original Rangemaster was not a pedal, but a box meant to be placed on top of the amplifier. The circuit makes use of a single OC71 or OC44 germanium transistor. One can hear the Rangemaster in many Queen songs, a good example being Procession from Queen's second album, Queen II. Tony Iommi is another Rangemaster user, and can be heard using one modified by a roadie on many Black Sabbath recordings.
An alleged early user of the Rangemaster was Eric Clapton, who supposedly used one around the time of John Mayall's Blues Breakers with Eric Clapton album, in combination with a 1960 Gibson Les Paul Standard and a Marshall Bluesbreaker. This connection is often used to market modern clones of the circuit and contributed a lot to its popularity in recent years, even though there is no evidence that Clapton ever used one. 
Just like the Dallas Rangemaster, the Hornby Skewes treble booster was a desktop unit.
While early Hornby Skewes Treble Booster units used a germanium transistor, the later, better known version features a silicon transistor. Rumours about a JFET version may source from a misread part number.
Vox made a variety of boosters that were meant to be plugged directly into amps or guitars, including the model V806 Treble Booster. Roger McGuinn installed one into his Rickenbacker guitar in the 1960s.
Electro-Harmonix used to make treble boosters in two different enclosures. The Screaming Bird was a plug-in device, whereas the Screaming Tree was a foot-pedal. The circuits were supposedly identical. In 2009 the pedal was reissued, bearing the Screaming Bird name.
Colorsound Power Boost
The Colorsound Power Boost is a treble and bass booster that runs on 18 volts, using two nine-volt batteries. David Gilmour used this orange coloured unit, but is often misunderstood to have used an Orange brand Treble Booster. Other notable users include Gary Moore
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