D*A*M Tone Bender MKII SCB

The D*A*M Tone Bender MKII SCB is a germanium fuzz pedal built by D*A*M for Sola Sound Ltd of London. It is a Tone Bender MKII based on the earliest known version of the circuit, and the SCB in its name comes from the smaller circuit board it is built on¹. Where the conventional MKII most players know carries three transistors on a larger board, the SCB recreates the earliest arrangement, right down to details like the absence of a pull-down capacitor on the input¹.

D*A*M describes the pedal's character in the maker's own words: the gain is only just pushing past that of its OC84-loaded MKI.5, while the tone is a little more choppy and heavy in artifacts, generally brighter, more crunchy, with more teeth and claws at full Attack¹.

What the SCB does differently from a standard MKII

The Tone Bender MKII was a three-transistor fuzz circuit that closely resembled the earlier two-transistor Tone Bender, with an extra transistor gain stage added in front². The earliest Sola Sound-branded MKIIs were not even new builds: the builders modified existing MK1.5 Tone Benders to the new three-transistor specifications, and at least one 1966 version was simply a two-transistor MK1.5 housed inside a Professional MKII branded enclosure². The conventional "large board" MKII followed from 1966 to 1968, and the Sola Sound-branded version of it was apparently built in relatively small numbers compared with the Vox and Marshall-branded MKIIs².

The SCB takes the other path. It is built on a smaller circuit board, which is the origin of the name, and it follows the earliest known version of the circuit rather than the later large-board layout¹. Two circuit details mark it out:

• It lacks the pull-down capacitor on the input, a component later MKIIs carried¹.
• Its gain is only just pushing past that of D*A*M's OC84-loaded MKI.5, rather than the higher output of later MKII builds¹.

D*A*M's builder used Anthony Macari's own Tone Bender as the reference point for the pedal, with a smattering more gain¹. In the maker's description, the tone, in keeping with the units of this type the builder has seen, is a little more choppy or heavy in artifacts, generally brighter, more crunchy, with more teeth and claws at full Attack¹.

Attack and the OC75 transistors

The Attack control is the MKII's fuzz or drive control, and on the SCB it is where the pedal's aggression lives: D*A*M describes the pedal as having more teeth and claws at full Attack¹. This matches the MKII convention, where the knobs are marked level and attack³.

The transistors are the heart of the story. The SCB uses OC75s, black glass and for the most part unbranded¹⁴. The original Sola Sound MKII Tone Bender sports a three-transistor OC75 circuit based on the MK1.5 version with an additional amplifier gain stage⁵, and the MKII circuit featured three Mullard OC75 transistors, though the pedal was also later made with three Mullard OC81D devices⁶. The shift from OC75 to OC81D transistors can also be observed in MKIIs supplied to Vox and to Marshall and Rotosound, with late-production Vox examples dating to 1968 coming with Mullard OC81Ds⁷⁴.

For comparison across the family, the MK1.5 that preceded the MKII typically used two Mullard OC75 germanium transistors⁸, and British Pedal Company's own manual notes that its OC75 MKII model offers more bite than the OC81D model⁹.

History: built by D*A*M for Sola Sound

The Tone Bender was introduced to the musical instrument market by Sola Sound in 1965, and the Professional MKII was originally designed by Gary Stewart Hurst and produced by Sola Sound back in 1966¹⁰¹¹. Sola Sound manufactured the MKII circuit for a number of different companies as the OEM during that period, including the well-known version supplied to Vox via Macari's Musical Exchange².

D*A*M's involvement with the current pedals goes back to the builder's study of surviving vintage units. The builder has been making Tone Benders since 2002, having studied a large percentage of the vintage units that survive to this day¹². As of July 2009, D*A*M began producing the Tone Bender Professional MKII for Sola Sound¹³. The builder frames the arrangement plainly:

D*A*M is purely the builder and cannot supply the SCB to the public. Anyone interested in the project is directed to contact Macari's in London, the shop that has sold the Tone Bender line since the 1960s¹⁰¹²¹⁴. The same arrangement covers the other D*A*M-built Sola Sound reproductions, including the D*A*M Tone Bender MKIV and the D*A*M System Tone Bender MKI.

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