Here’s some ad copy from my online listing that might shed a little more light for the troubled:
The Rochambeau Musical Apparatus Mudlark is a high dynamics fuzz with the two band equalization.
Primary order switch (toggle at left) assigns the order in which the fuzz stage and equalizer stage are presented to the signal (after an initial gain stage and before a recovery gain output stage). The position of this switch is also reflected in the color of the effect engaged LED; RED = input into EQ into fuzz into output, and BLUE = input into fuzz into EQ into output.
Secondary mode switch defines the character of the device, one position being a touch more refined and the other leans more toward being unruly. In blue unruly, for example, the unit will for all intents and purposes function as an oscillating fuzz.
Please note, due to the type of fuzz subsection (bias clipped NPN/PNP cascading pair) the RMA Mudlark sits in more of a gated fuzz realm, which, while doing wonders for spurious floor noise between notes (unless in the oscillation combination referenced above) it does somewhat take apart and rearrange note taper a bit. I have found this to be more pleasing when applied synthesizers and drum machines than standard fare in fuzz, though I imagine some may object to the nuance of their tender tones gradual decay being subjected to the roiling churn of wandering electrons leading to a somewhat sputtered finish.
The dynamics aspect can be explored in more depth with lower settings of the “song” (please note, this is the Mudlark’s song, not your own) control, which benefits minor adjustments by being the largest knob on the box. In some positions the dynamic response to ones playing can be staggering, and it may be preferred to simply run this control at the wide open/toward full clockwise for more conventional behavior, the lofi honks available in the CCW region are something of an acquired taste (and often benefit from output level compensation, but be careful – this thing can get quite loud)
Regarding the internals picture, the unit for sale here is the neater of the two (the other being initial run prototype). The ICs pictured are only handling signal insofar as the 4066 ICs acting as (post gain) switches to route order and mode functions, all of the heavy lifting is done in discrete transistor realm.
The enclosure is bent steel, finished by hand and clearcoated to protect both finish and your equipment. The box measures roughly 4 inches (~10 cm) wide by 5.5 inches (14cm) long and 1 inch (2.5 cm; sidewall measured, from base to top of song knob is closer to 2 inch/5cm) tall.
Operates on 9 volt negative tip (diode protected).