History of the Tone Bender

Tone Bender MK1

The UK fuzz box phenomenon began in 1965 when electronics engineer Gary Stewart Hurst designed an effects pedal called a Tone Bender. The first version of this Tone Bender is referred to as the Tone Bender MKI. The MKI was a three transistor circuit that was based upon the Gibson built Maestro Fuzz-tone that was modified by Hurst to produce more sustain than its American counter part. The story goes that guitar legend Vic Flick, the man responsible for the James Bond Theme, brought a Fuzz-tone (FZ-1) to Hurst and requested the sustain to be increased. The Tone Bender was one the first ever British made Fuzz box available to the public and sold for 14 guineas. It was housed in a folded steel chassis and finished in gold & black Hammerite paint with some of the very early units housed in a wooden and steel enclosure.

The first few available Tone Benders were sold as Gary Hurst designed units and were not sold as Sola Sound pedals. These pedals had what appears to be dry letter transfers for the labelling which was hand applied, note how little labelling is actually left intact on the example on the right. Probably only a very small number were made before the pedal was labeled using a silk screened approach. These silk screened MKI’s did state the unit as a “Sola Sounds Ltd” pedal, note the plural on Sound.

The MKI was a three transistor circuit; no doubt about it but it was in no way similar to its three transistor successor, the Professional MKII. The MKI circuit is loaded with a single Mullard OC75 and two Texas Instruments 2G381 devices. It was based upon the FZ-1 circuit as where many of the early fuzz boxes to arrive on the scene but had significant modifications that made for a much stronger and more powerful fuzz sound. Firstly was the fact it was able to use a 9 volt supply not 3 volts in the case of the FZ-1. This with the tweaking of certain resistor values gave the longer sustain time and also much more output volume. The two pictured MKI’s on this page when side by side do sound different. The slightly earlier model with the dry letter labelling has much more of a FZ-1 character to the tone and is very reminiscent of Jeff Beck’s use of a MKI on tracks such as “Heartful of Soul” The silk screened model is much more focused and tighter sounding, you can defiantly hear how the circuit has been refined and tuned from one pedal to the next. This MKI is classic Mick Ronson fuzz through and through. The output level is well over double that of the other MKI and when correctly dialled in has fierce amounts sustain with truly astounding clarity for such an old device.

The circuit construction is the point to point technique to the maximum. The board is blank compressed fibre board and is only being used to actually mount the components; each part is wired directly to the next with the board only being held in place by being directly wired to the pots. Quite crude in design but very ingenious. I have seen probably one of the first ever made MKI’s which had a circuit that was made on strip board and not like the one pictured here. This circuit was covered in black paint to hide the component values so is very likely this is a prototype unit.

The MKI also featured some very some high quality features within the rest on its construction which was to set the standard for the Sola Sound made Tone Benders to come. Shielded cable was used on all input and output cabling, something most manufacturers do not do to this day, which helped to give excellent interference rejecting properties and good noise levels. True Bypass switching as standard. Usually seen as a modern feature in pedal building, the MKI had this way back in 1965. As far I have seen this is the first time true bypass switching was actually used in a pedal.

Some famous users of the MKI unit included Pete Townshed of the Who, Jeff Beck of the Yardbirds, Mick Ronson and the Beatles. The MKI was the first Tone Bender the Beatles were to use and it first featured on the album “Rubber Soul” Paul McCartney actually used the MKI on the bass track on the recording “Think for Yourself” Mick Ronson was a dedicated user the MKI from his time with “The Rats” up until he played with the “Spiders From Mars” This was Mick’s main fuzz box for over a decade not a Vox Tone Bender as is commonly assumed.

Distant Cousins, The Zonk Machine

Being one of the first on the scene the MKI was obviously a big influence on what was to come. One of the more famous MKI influenced fuzz boxes and now almost as legendary as its golden cousin was the John Hornby Skewes Zonk Machine. A little more wacky in the graphics department, but not a heavy duty or robust as the MKI, the Zonk Machine was almost identical in its circuitry. Made between 1965 and 1966 in Leeds, England the Zonk Machine like the MKI was only made in small numbers before the pedal was updated with a more modern and easier to produce unit.

The Transition: MKI.5

In early 1966 the Tone Bender received its first major changes; the folded steel case was replaced with a sleeker more futuristic looking sand cast aluminium design finished in a grey Hammerite paint. It featured a newly designed two transistor circuit that used two Mullard OC75 devices. The name Sola Sound again did not appear on the case and the silk screening just stated the unit as a Tone Bender. This particular two transistor circuit is said to have been leaked/loaned to Arbiter who went on to release the legendary Fuzz Face later that very same year. This is also the circuit type that was used by Vox in their Italian production, again of the same year, for the Vox Tone Bender.

The MK1.5 was the first Tone Bender to use strip board construction and the metal supporting bracket that also acted as a one point grounding system for the pedal. Again following on from build techniques of the MKI the MK1.5 displayed heavy use of shielded cable, isolated in and output sockets and grounded true bypass switching. The Tone produced by this circuit was much denser and not as heavily saturated as the MKI but was much more of a user friendly fuzz box and not too unsurprisingly it sounds similar to an early Arbiter made Fuzz Face. It pretty much sounds how you want a vintage Fuzz Face to sound.

Professional MKII

Only a small number of the two transistor Tone Benders were produced before the change to the famous three transistor Tone Bender Professional MKII. The MKII circuit featured three Mullard OC75 transistors but the pedal was also made with three Mullard OC81D devices, which were actually designed for use as audio drivers in radio equipment. The OC81D MKII now has an almost legendary status because of its rarity and also because it displayed excellent sonic capabilities and offered the guitarist the ability to control the amount of fuzz with their guitars volume control. Again the construction of the circuit was made using strip board.


You can actually see the circuit transition from the MKI.5 to the MKII on the MKII circuit pictured below. You’ll see that the board is the same size and uses a lot of the same components placements as the MKI.5 circuit pictured above. This example shown is one of the earliest ever made Sola Sound MKII’s. It also has the same enclosure casting as the MKI.5 and with the smaller older circuit type gives strong evidence that the MKII was actually first made with the Mullard OC75’s before the use of the OC81D’s.

Vox Tone Bender Professional MKII

Sola Sound also produced the now increasingly popular Tone Bender MKII in varies guises for Marshall, Rotosound and also produced a Tone Bender Professional MKII for Vox which confusingly could actually pre-date the Italian Vox Tone Bender. The Professional MKII is a really rare pedal indeed but the Vox example is almost mythically rare. Built to the same high standard as the Sola Sound model the only differences being the Vox screen printing and the silver grey Hammerite as apposed to the dark grey used for the Sola Sound model.

This is particular pedal a fine example; you could say it’s in time warp condition. This is the MKII that everyone wants. It features the OC81D’s and has a fuzz tone to die for. The OC75 versus OC81D isn’t a clean cut debate by any means, one isn’t actually better than another it does and can vary from one unit to another.

Marshall Supa Fuzz

One of Sola Sound’s most popular MKII side lines was the Mighty Marshall Supa Fuzz. Made from 1966 right through into the 1970’s it was the longest living MKII variant. The very first examples of the Supa Fuzz actually featured a MKI circuit variation with a crude tone filter and pre-set gain levels hence the Fuzz/Attack control on all later models actually being labelled as “Filter”. The MKI variant Supa Fuzzes are really scarce pedals indeed, I only actually know of two examples so it could be possible it never made it past the prototype stage. These models also have the controls set closer together which explains why the screen printing on the MKII variant Supa Fuzzes have misaligned labelling. The main production Supa Fuzz from 1966 through 1967/68 was made almost in exactly the same way as a Sola Sound MKII, the only difference being that some units had a limiting resistor on the Filter control so the amount of fuzz could only ever reach 90% saturation. A part from this the MKII and Sola Sound made Supa Fuzz were identical. The Supa Fuzz only received circuit changes when the strip board construction was abandoned in the late 1960’s for PCB construction. These examples also have a different enclosures casting and do sound a little darker. The Marshall Supa Fuzz was only ever made with OC75’s, never OC81D’s. I have seen a few later models that had AC128’s in the first stage but these could purely be due to repairs. I have never actually seen a un-modified Supa Fuzz that had OC71’s fitted from stock.

Vox Tone Bender

Probably the most iconic Tone Bender of all, say the words Tone Bender and this is the pedal most will think of. Originally made in 1966 the Vox Tone Bender had the longest run of all and was still being made in some form or another in the mid to late 1970’s. While this pedal is branded as a Vox it doesn’t mean it was a British made pedal, they were actually made in Italy. It could have been possible that the earliest units were made in England, as with the early Vox Wah pedals, but there is no direct proof for this. The very first Vox Tone Benders did have slightly different component values but most obvious of all had an OC76 transistor in the second position within the circuit. These early Vox units were fitted with a SFT337 and an OC76 and also had the input capacitor mounted beneath the circuit board. Models from approx 1967 still used the SFT337 but in place of the OC76 used a SFT363E and featured a top mounted input capacitor. If you compare the two circuits below you can see the obvious differences, this could purely be changes in suppliers as more units were produced or could be possible evidence for some of the earliest Vox units being made in England.

The tone produced by this circuit can be a little shocking at first if you are expecting a deep brick wall type of Fuzz Face type tone. The treble content is quite high for a fuzz pedal but makes for a very unique sounding effect and an excellent pedal to be used with dark sounding British valve amplifiers.

In 1968 Sola Sound introduced the Tone Bender MKIII…this is another story.