Sola Sound released the Tone Bender MKIV, approximately during the year of 1970, during which the model was regularly advertised in Beat Instrumental & Melody Maker publications. At the time, the only thing that set the MKIV apart from the Tone Bender MKIII that they were already producing for Vox, was the fact that the MKIV came in a slightly different enclosure, and that the model was printed with different graphics.
In the same way that Sola Sound were manufacturing their Tone Benders [MK1.5, Professional MKII & MKIII] under different names throughout the mid-to-late 1960s, the MKIV was also supplied to various different companies during the 1970s. The circuits & enclosures that Sola Sound were using in the early-to-mid-1970s for their own ‘Sola Sound Tone Bender’ were identical to the ones built for companies like Carlsbro and Park.
Tone Bender MKIV, “bendy” logo
The earliest versions of the Tone Bender MKIV were formally branded as ‘Sola Sound Tone Bender Mark IV’ pedals, and were housed in grey, pressed steel enclosures. To help to differentiate these early Tone Bender MKIV pedals from later examples, collectors have in recent years began informally referring to them as having “bendy” or “spaghetti” graphics (referring to the way that the ‘Tone Bender’ lettering has been stylised).
Slightly later examples featured the same graphic design, but came in both yellow and in orange colour schemes instead. The Tone Benders in these yellow and orange enclosures disproportionately resurface in central Europe, despite having been built in Britain. This is indicative of Sola Sound’s distribution model at the time. (Photo credit: S. Castledine, W. Merkel & eBay.com)
Tone Bender MKIV, “Batman” logo
By approximately 1971 (according to date codes on surviving examples), Sola Sound had redesigned the artwork on this model and begun production of one of the most recognisable versions of all of the Tone Benders. The model designation of the Tone Bender MKIV was removed, and Sola Sound’s fuzz box was once again, known simply as the ‘Sola Sound Tone Bender’. Internally, however, the circuits of these newer pedals remained unchanged.
Collectors in recent times have begun informally describing this version of the Tone Bender MKIV as being the version with the “Batman” logo, referring to the cartoonish stylisation of the ‘FUZZ‘ logo. Early pedals with this design scheme were printed with red & black ink, onto yellow enclosures. Sola Sound soon settled on a grey colour scheme, and this was how the Tone Bender would appear until the late 1970s.
The Tone Bender MKIV gradually evolved over the course of production, and this is reflected by the change in the electronic parts that were used, and in the overall construction of the circuits. The images above demonstrate the changes in the MKIV’s circuitry over the course of the 1970s. (Photo credit: S. Castledine & Crave Guitars)
MKIV’s built during the first half of the 1970s featured a three-transistor circuit that was loosely based on the Baldwin-Burns Buzzaround. By the late 1970s, the grey Tone Benders with the “Batman” logo were being built with a silicon-transistor fuzz circuit, loosely based on the Electro Harmonix Big Muff Pi. Sola Sound’s development of the circuits inside Tone Bender MKIV pedals is mirrored by the development of the same circuits in the Tone Bender MKIII, which still being supplied to Vox, in parallel with these pedals.
The Tone Bender MKIV was finally discontinued in the late 1970s.