Coda Effects Black Keys Big Muff

The Coda Effects Black Keys Big Muff is a DIY Big Muff clone fuzz pedal, documented by the builder behind Coda Effects in September 2015. It is not a stock copy: the builder "mixed a russian green muff with the Hoof and Ram's Head values to have something nice," and added a fourth knob, a Mids control, on top of the usual Big Muff three¹.

The controls

The pedal keeps the three standard Big Muff controls and adds a fourth: "There are the 3 usual controls of a Big Muff: volume, tone, sustain, and a supplementary one: mid control!"¹

The builder's verdict on the two new-arrangement knobs was mixed: "Evenif the Mids knob works really really well, the tone knob is weird. I guess it is because of the logarithmic scale." The Mids knob is the part that carried forward: the same AMZ resistor-plus-potentiometer technique, with the 25k linear Mids knob and 2.2k R5-1, is what he later used for the Big Muff "Black Keys" build writeup on his tonestack page²¹.

LED clipping and the experiments behind it

Instead of the classic 1N914 diodes, there are LEDs on the board as the clipping elements. That choice shapes the character of the pedal, and the builder tried alternatives before settling on red¹:

• Red LEDs: the chosen clipping, giving the less compressed, less saturated character described below¹
• Blue LEDs: the builder found that "The sound is really different when you swap for blue LEDs, in fact the transistors started to saturate, and the muff was" much more mushy, so red was judged better¹
• Germanium AC187 transistors in the clipping section, as in the Hoof: the builder reported trying "to use germanium transistors (AC187) for the clipping section, like in the Hoof, but I was not really satisfied," losing output volume with little tonal difference¹

So the LED clipping is the main lever between this pedal and a stock Green Russian voicing: same board, different diodes, noticeably different fuzz¹.

How it sounds compared to a Green Russian Muff

The builder's own comparison puts it nearer to another fuzz than to the Muff it is based on: "it sounds really closer to the Hoof than a Green Muff. I think this is mainly because of the LED clipping diodes." His summary of the character: less compressed, less saturated, but still quite heavy¹. For a player deciding between this and a straight Green Russian clone, the trade is the added Mids knob and the LED-clipping voicing against the classic green muff sound, which is one LED swap away on this build¹.

The build: PCB and enclosure

The pedal is built on the Musikding "Der Muff" PCB. The builder notes "this PCB is quite cheap (4.5 euros), but it is monolayer, and thus quite big. So it can only fit a 1590BB enclosure." The 1590BB enclosure was finished by hand: sanded with 180 grit sandpaper, then 480 grit, and varnished¹.

Elsewhere in the signal path he used Panasonic SMF capacitors and 2N5089 transistors, with an MPSA18 for the output transistor, "which gives a high volume"¹.

Questions