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The White Russian - My DIY Big Muff Pi

Here's my take on the Big Muff Pi. I started with the "Green Russian" circuit and added some modifications that make it my most versatile dirt pedal. It runs the gamut from clean boost to full on fuzz.

I used the Tagboard Effects layout as a base. I'll start with the modification that's not obvious from looking at it which is the tone stack, I modified the values to more closely match the original circuit and provide what I thought was a better response. 

As for the extra knobs and switches I'll run through them in order.  

Bias Knob

This 100k pot replaces the 100k bias resistor on the 4th stage transistor, turning this to the right brings the value down and further mis-biases the circuit. This lets you get some interesting effects even if it's not the most useful. 

The further right the quieter your sound and the more gated it becomes, at the extreme settings you can get some truly weird noises where only your transients get through. 

Tone Wicker 

This is lifted from the EHX pedal. When I was listening to demos I loved the fuzz of the Green Russian but also the additional clarity that could be achieved with the Tone Wicker, why settle for either when I can have both?

This is one of my favourite switches on the whole pedal, I can best describe the result as lifting a blanket off the tone. It really does open up the high end. Listen to some demos of the EHX version to see what I mean. 

Mids

This switch is the same as in the Tagboard layout but with different values. I used Tone Stack Calculator to work out which cap values would give me a flat response and a mid hump. 

Anyone who has used a Big Muff will know that it scoops mids quite a bit this switch allows you to have the classic Big Muff sound while still retaining presence in the mix.

Diodes  

The last and perhaps biggest change, the diode switches. Each switch allows me to go from stock 1N4148s to red LEDs and even lift the diodes entirely in the centre position. 

The LEDs provide a volume boost and headroom increase while still retaining that fuzzy character of the Big Muff. Great for stacking pedals or aiming for a more distortionesque response.  

The diode lift is where this really shines in my opinion, the first thing you notice is how loud the pedal is, with the sustain cranked you're hitting the rails of the transistors and clipping that way. At lower sustain levels the pedal starts to turn into an overdrive providing just a small amount of crunch. 

You will notice the two switches, there's one switch for each clipping stage. Stage 3 has the most effect on the overall sound whereas stage 2 is very subtle and will likely only have an effect if you're boosting into the pedal.

Conclusion

I'm not joking when I say this can do a clean boost, with a flat mids response, tone wicker engaged, the diodes lifted, and just the right settings on the knobs you can't notice a difference between the pedal being on or off. 

Once you've found this point you can really start to shape your tone, dialing in just the right amount of dirt and getting the EQ spot on. It really is the ultimate dirt pedal.

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