FOGBOW MKI TONE BENDER
FOGBOW (formally called Red Sam) is my take on the Tone Bender MKI. There are limitless ways to tune this circuit for different results. I favor moderate gating and compression; thick saturation; and copious crackle, sputter, and swirl in the decay. These qualities make this circuit unique. Tuning in dubious improvements (like smooth sustain and minimal gating) spoils the special personality of this effect.
For the cognoscenti among us, I offer some of the obscure variations found in the old ones, but, if you’re not aware of these quirks, don’t worry about them.
The Fogbow is available in standard, Focus, and Old Pal construction.
AN MKI HISTORY
In 1965 an Englishman named Gary Hurst developed the Tone Bender MKI as an (ostensibly) improved successor to the American-made Maestro FZ-1. The MKI circuit was essentially lifted from Maestro’s watershed effect, but Hurst rebiased it to operate at 9v, and altered the output section to increase low-end. These modifications also enhanced sustain, saturation, and compression.
Original examples of this effect are rare, and, as I understand, the circuit was all but forgotten until the current century. The few surviving examples vary considerably one from another. I imagine these effects were, to some degree, assembled with whatever components were available at the shop around the corner, which would explain the variations.
In original units, it’s not uncommon to find remnants of components chopped from the circuit during tuning. Hunts capacitors, Erie and Alan Bradley resistors, and a transistor trio consisting of one Mullard OC75 and two Texas Instruments 2G381 are usually found in old ones, but a definitive parts schedule was never established. Resistors, for example, were often spliced in to improve the bias of particular units—a 47K resistor from output to ground here, a 330k resistor piggybacked in to improve bias there . . .
To hear the MKI sound, I recommend Mick Ronson's work with David Bowie, or the Heavy Blanket album featuring J Mascis.
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