The Vox Tone Bender Professional MKII is a germanium fuzz box built by Sola Sound in London and sold under the Vox name. It is one of the best-known versions of the Sola Sound Tone Bender MKII, a three-transistor fuzz circuit that Sola Sound supplied, through Macari's Musical Exchange, to Vox as well as to Marshall (as the Supa Fuzz), Park (as the Fuzz Sound) and Rotosound (as the Fuzz Box) with minor alterations123.
Vox-branded MKII units appeared by early 1967, and the circuit was discontinued in 1968, when Sola Sound introduced the Tone Bender MKIII, which it also supplied to Vox14. Original Vox examples are exceptionally scarce: one history of these pedals describes the Vox version as "almost mythically rare"5.
How it relates to the Sola Sound MKII
The circuitry inside the Vox Tone Bender MKII remained largely unchanged from the Sola Sound version, although the choice of resistors and capacitors was gradually updated over production1. The differences a player can see are on the outside: Vox screen printing and a silver Hammerite finish instead of the dark gray of the Sola Sound model15.
Some of the earliest known Vox-branded units were in fact Sola Sound-branded pedals with the Sola Sound name crudely obscured by a black bar and replaced with "Vox"12. The graphics were quickly redesigned, and the Vox logo became much more prominent on later versions from 1967 to 19681. The knobs changed too: instead of Bulgin "chicken head" knobs, these pedals featured tall silver-topped knobs, similar to the current Cliff K5 knob1.
The Sola Sound-branded MKII itself went through several versions during its short life2:
| Version | Period | Description |
|---|---|---|
| MK1.5 conversions / "short board" | 1966 | Existing MK1.5 Tone Benders modified to the new three-transistor specification2 |
| Two-transistor MKII | 1966 | A two-transistor MK1.5 housed inside a "Sola Sound Professional MKII" branded enclosure2 |
| Conventional "large board" MKII | 1966 to 1968 | The standard three-transistor circuit, built in relatively small numbers2 |
Transistors and circuit details
The Tone Bender MKII was a three-transistor fuzz circuit2. Early examples of the Vox version have been sighted with triplets of either Mullard OC75 or Impex S3-1T germanium transistors, and late-production examples dating to 1968 came with Mullard OC81D transistors1. The same shift from OC75 to OC81D can also be observed in the MKII Tone Benders supplied to Marshall and Rotosound1.
The input capacitor changed alongside the transistors. During the OC75-transistor period for Vox, the input-to-ground capacitor was 15nF; with the OC81D versions it was 10nF, before being dropped altogether, as the very last Vox MKII units were built without an input capacitor at all1. Earlier examples were also built with slightly larger value input and output capacitors1.
The original Sola Sound, Vox and Colorsound Tone Bender units were equipped with OC81D transistors, which are not widely available today6.
Why it is so rare
The Vox Tone Bender Professional MKII was built for roughly two years, from early 1967 until the circuit was discontinued in 19681. The Sola Sound-branded version was itself built in relatively small numbers compared with the Vox and Marshall-branded MKII2. The result is that surviving Vox examples are extremely hard to find, and the pedal's rarity is part of why later builders have recreated it.
The JMI Professional MKII Tone Bender reissue
After the design had been out of production for over 40 years, the Vox Tone Bender Professional MKII became available again from JMI78. The JMI Professional MkII Tone Bender is a replica of the OC81D-equipped 1967 MK II Professional Tone Bender, made by JMI Amplification. It has a sand-cast aluminum chassis, germanium transistors, and uses the original circuit8.
"After being out of production for over 40 years, the VOX Tone Bender Professional MKII is available again from JMI"
Separately, D*A*M began producing the Tone Bender Professional MKII for Sola Sound as of July 20099.
Other replicas of the OC81D version
The OC81D-equipped MKII has been recreated by several makers. British Pedal Company makes a Professional Tone Bender MKII OC81D, and in BPC's own manual the OC81D model "offers smoother sustain" while the OC75 model "offers more bite than the OC81D model"108. BPC also describes its MKI.5 Tone Bender OC81D version as having "a unique tone which cannot be replicated by the often offered 3x OC75 version"10.
Where it sits in the Tone Bender story
The Tone Bender began with Sola Sound's original fuzz box from 1965, now given the "MKI" designation11. A two-transistor "MK1.5" followed, and a modified version of that circuit became the Tone Bender Professional MKII12. The demise of the MKII in 1968 resulted in Sola Sound's invention of the Vox Tone Bender MKIII, which it continued to supply to Vox well into the 1970s14. Premier Guitar's history of the pedal notes that the Tone Bender went through "a succession of revisions that yielded two different versions of the MKI, a 'transitional' MK1.5, and the Tone Bender Professional MKII"3.
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Questions
How does the Vox Tone Bender Professional MKII differ from the Sola Sound MKII?
The circuitry is largely the same three-transistor fuzz circuit, with only resistor and capacitor choices updated gradually over production. The visible differences are the Vox screen printing on the face and the enclosure finish: the Vox version was painted in silver Hammerite instead of the dark gray of the Sola Sound model. Some early Vox units were actually Sola Sound pedals with the Sola Sound name covered by a black bar.
When was the Vox Tone Bender Professional MKII made?
Vox-branded units appeared by early 1967, when Sola Sound scaled down printing its own brand name on the pedals. Production ran until 1968, when the Tone Bender MKII circuit was discontinued and Sola Sound moved on to the Tone Bender MKIII, which it also supplied to Vox.
What transistors did the Vox Tone Bender Professional MKII use?
It is a three-transistor germanium fuzz circuit. Early examples came with triplets of either Mullard OC75 or Impex S3-1T transistors, and late-production examples dating to 1968 came with Mullard OC81D transistors. The same shift from OC75 to OC81D also appears in MKII Tone Benders supplied to Marshall and Rotosound.
Why is the Vox Tone Bender Professional MKII so rare?
It was built for only about two years, from early 1967 until the circuit was discontinued in 1968, and the Sola Sound-branded version of the same pedal was itself built in relatively small numbers. One history of these pedals describes the Vox example as almost mythically rare.
What did the enclosure of the Vox Tone Bender Professional MKII look like?
It used the same pressed steel enclosure as the Sola Sound MKII, painted in silver Hammerite rather than dark grey, with Vox screen printing on the face. The earliest units kept the Sola Sound graphics with the brand name covered by a black bar and replaced with the Vox name. Later versions carried a much more prominent Vox logo.
What is the JMI Professional MKII Tone Bender?
It is a replica of the OC81D-equipped 1967 MK II Professional Tone Bender, made by JMI Amplification. It has a sand-cast aluminium chassis, germanium transistors, and uses the original circuit. It brought the Vox Tone Bender Professional MKII back after the design had been out of production for over 40 years.
Sources (12)
- Vox Tone Bender Professional MKII • Fuzzboxes, Fuzzboxes.org, 2021-05-20
- Sola Sound Tone Bender Professional MKII • Fuzzboxes, Fuzzboxes.org, 2021-05-18
- Stompbox Classics: Tone Bender, Premier Guitar, 2009-09-18
- Vox Tone Bender MKIII • Fuzzboxes, Fuzzboxes.org, 2021-05-30
- A Little History, www.stompboxes.co.uk, 2017
- PUTB_v2 (1), GuitarPCB.com, 2018-06
- TONEHOME, TONEHOME - the World of Vintage Guitar Effects Pedals
- JMI Professional MKII Tone Bender, Vintage Guitar magazine, 2013-01-09
- Sola Sound Ltd, stompboxes.co.uk (D*A*M), 2019
- BPC-Product-Manual-2021-V1.pdf, British Pedal Company, 2021
- Tone Bender 'MKI' players list • Fuzzboxes, fuzzboxes.org, 2026-02-22
- Sola Sound Tone Bender 'MK1.5' • Fuzzboxes, Fuzzboxes.org, 2021-05-18
