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Sola Sound Tone Bender MKI
The first incarnation of the Tone Bender was a three transistor circuit based on the Gibson Maestro Fuzz-Tone. Gary Hurst, a technician, began selling these in mid-1965. By September he was selling them through the Macari brothers' Musical Exchange shops. Early incarnations were housed in wooden enclosures. Later on folded steel enclosures were used.
Sola Sound Tone Bender ("MK1.5")
This version of the Tone Bender is a two transistor circuit designed by Gary Hurst, upon which the better known Arbiter Fuzz Face and Italian-made Vox Tone Bender are based. It is essentially a negative feedback amplifier.
Although this was de facto a second version, no version number was used on its case. To be able to tell it apart from the MKI and MKII it is known as the "MK1.5" today.
This successor of the original Tone Bender was available at the latest, February 1966. The electronics are contained in a sand-cast aluminum enclosure, with sheet metal (steel) base plate.
It was also available in different guises as Sola Sound made prototypes and built commercial units for other companies.
The most common non Sola Sound mk1.5 was the Italian VOX Tone Bender. The circuit was built onto a PCB and housed in an identical enclosure painted with black textured powder coat and sported an aluminum panel for the controls.
The negative feedback circuit found its way into many products around the period. Many were built into VOX amps, these were claimed to be used by many Pro users to get 'fabled tones'. Others found homes as the VOX Distortion Booster and Fuzz Face.
Sola Sound Tone Bender Professional MKII
Sola Sound produced the circuit for Vox, Marshall and RotoSound as well. These units were named Vox Tone Bender Professional MKII, Marshall Supa Fuzz, RotoSound Fuzz Box. There also was a version of the short lived Rangemaster Fuzzbug containing this circuit. Other variants may exist.
The Sola Sound and Vox version used the same sturdy, sand cast metal enclosure designed by Hurst as the MKI.V version. In fact, many Sola Sound branded MKIIs were probably leftover stock of MK1.5s with the circuit modified to MKII specs and a "Professional MKII" silkscreen added, presumably to differentiate them from the earlier version.
By November 1966 the pedal was being advertised in Beat Instrumental magazine, marketed as a "Gary Hurst Design". It remained in production until early 1968. Marshall continued producing a slightly different looking version of the Supa Fuzz until 1972 or longer.
After being out of production for over 40 years, the Sola Sound Tone Bender Professional MKII is available again from Macari's since 2009 as part of their Vintage Series of pedals. It's being made D*A*M Pedals, South Yorkshire.
Sola Sound Tone Bender MKIII, IV, Tone-Bender Fuzz
The Sola Sound Tone Bender MKIII, and later Tone Bender MKIV, featured a tone control. It's a three transistor circuit with a germanium diode, that came in several different enclosures and is closely related to the Burn's Baldwin Buzzaround. It was available under different names and brands. Most MKIII Tone Benders are branded as Vox. The Sola Sound version is scarce. The Park Fuzz Sound and Rotosound Fuzz Box were also available with this circuit. By 1969 the same circuit was sold in a smaller updated case as the Sola Sound Tone Bender MKIV. The larger MKIII version was sold concurrently. The Carlsbro Fuzz and Park Fuzz Sound were available in the MKIV enclosure as well. By 1971 the MKIV's graphics were updated, marketing the device as the "Tone-Bender Fuzz" from that point onwards. By the mid-70's it was also available in another different enclosure, branded as the CSL Super Fuzz. The circuit was discontinued around 1976 and reintroduced in 2012, once again with MKIV graphics.
A short lived version of the MKIII with only two controls, containing a circuit with four silicon transistors exists. It probably predates the more common germanium version.
Colorsound Supa Tonebender
Colorsound Jumbo Tone Bender
The Jumbo Tone Bender is a three transistor circuit based on the Electro-Harmonix Big Muff π. Sola Sound made this pedal under various names, in various enclosures and for various distributors. It can be found in a narrow Colorsound enclosure with the same graphics as the late germanium Tone Benders, a wide Colorsound enclosure, using Jumbo Tone Bender graphics, in Vox MKIII Tone Bender enclosures, in a different narrow enclosure rebranded as B&M (Champion) Fuzz, B&M Fuzz Unit, CMI Fuzz Unit, G.B. Fuzz, G.B. Fuzz Unit or Pro Traffic Fuzz Unit or in a smaller enclosure labeled as the Eurotec Black Box Fuzz Module. It was also part of the Colorsound Supa Wah-Fuzz-Swell.
The current "thin case" Tone Bender is using this circuit.
Vox Tone Bender
-  Intellectual Property Office - Tone Bender trademark
-  United States Patent and Trademark Office - Tone Bender
-  United States Patent and Trademark Office - Tone Bender Germanium Charged Fuzz
-  Pedal Porn - A little History
- Beat Instrumental No.29; September 1965
-  Vox Tone Bender Professional MKII
-  Marshall Supa Fuzz
-  RotoSound Fuzz Box
- Beat Instrumental - November 1966
- Macari's Musical Instruments of London
- D*A*M - Differential Audio Manifestationz
- Fuzz Central - Sola Sound ToneBender Professional MKII; schematics
- Fuzz Central - Colorsound Jumbo Tonebender; schematic
- Fuzz Central - Vox Tone Bender; schematics
- Effects Database - Gary Hurst Tone Bender MkI (wood)
- Effects Database - Gary Hurst Tone Bender MkI (metal)
- Effects Database - Sola Sound Tone Bender MkI
- Effects Database - Sola Sound Tone Bender Mk1.5
- Effects Database - Sola Sound Tone Bender MkII
- Effects Database - Sola Sound Tone Bender MkIII
- Effects Database - Sola Sound Tone Bender MkIV
- Effects Database - Colorsound Supa Tone Bender
- Effects Database - Colorsound Jumbo Tone Bender