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PiModulos

A module EHX Big Muff Pi clone PCB, the PCB can be populated with any version of the transistor Muff circuit

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A module EHX Big Muff Pi clone PCB. Can be used to make the Big Muff Pi fuzz pedal for guitar and bass. I take no credit for the development of the original circuit, I just made a simple PCB so I can make my own versions of the pedal quicker and easier.

PiModulos is supposed to be a modular EHX Big Muff Pi PCB that can implement as many versions of the transistor BMP circuit. So far two schematics have been created, one is for a triangle era muff they other is for a Skreddy Mayonaise, it has altered values and a midrange switch added. Also this PCB has pads for a few popular mods. The emitter mod, consists of bypassing the resistors to ground from the transistors, this can be implemented as a switchable feature. the result is a boost in mid range and gain/fuzz. The other mod is the skreddy tone switch mod that adds another cap in parallel with the one int he filter of the tone circuit, this gives a boost in midrange.

Musical expression is an integral part of our culture and music culture. The Pi Modulos modular assembly and ability to become any Big muff this PCB project will allow artists to sculpt their signature tone at the circuit level.

  • PCB Progress

    Adam Vadala-Roth05/14/2016 at 18:41 0 comments

    So I have been working on and off on the new PiModulos V2 PCB. For the most part component placement has been figured out, next will be fine turning placement, board size and then routing. Here is what I got so far:

    As you can see I decided to keep the tone switch or the tone wicker as EHX officially calls it, I found a nice switch that mounted nicely on the PCB so it stayed. You will also notice the connector pads on the sides of the board, those were intended for wiring the PCB into a pedal enclosure with a 3D3T switch, and 1/4 TRS connectors, I have since decided that I don't want to use this wiring style since it will be messy, so I'm gonna combine all the signals into a single connector and connect it to a dedicated PCB with a ribbon cable. Also the mid switch and additional cap are still in the tone circuit, I decided that I really should try it out since it might be something I really want for my personal sound tastes.

    So for PCB topology, its going to be a two layer board with the bottom layer acting as a ground plane. There will be minimal traces on the bottom with special care taken to prevent crosstalk and capacitive coupling between traces. As for trace width I will be using about 20-25 mil, its roughly the width that most pedals use from my observations and experience tearing them down. I'm also considering trying out OSHPark's new 2OZ copper service for added robustness, it cost the same as the regular services, oh yeah did I mention I will be fabbing with OSHPark lol.

    My design is sort of turning into a hybrid boutique meets industrial pedal, combining design elements of handwired pedals and the SMT mass produced designs made by the big manufactures, cant wait to see how it turns out! Stay tuned folks!

  • New Schematic

    Adam Vadala-Roth05/11/2016 at 01:57 0 comments

    Here is the newly revised schematic for PiModulos V2:

    Most notable revisions are a much neater layout and the components are numbered the same way they would be on classic Big Muff pedal PCBs and schematics. This revision still has the tone switch, I'm planning on keeping it if I can keep the PCB a certain size with it on there, otherwise it will left out.

    As for component choices and values, the schematic aims to match the Skreddy Mayonaise variant as close as possible. Some component values for some capacitor types are hard to find, so some compromises were made (e.g going with the closest value). I plan to try different component values when testing and assembling to get as close to the desired sound as I can.

    Moving on to layout, I'm in the middle of it currently and will be posting a completed board and OSHPark quote soon, so stay tuned!!!

  • Revised Design

    Adam Vadala-Roth05/10/2016 at 04:29 0 comments

    Hey all, as part of my current audio project kick I will be redesigning PiModulos entirely. I realized quite a few flaws in the design both schematic and board. Rather than correct the board as is I decided to do it all over again from the ground up. The new version will feature a much neater layout, integrated PCB mounted potentiometers, power jack, and instrument jacks. I am debating whether or not to include all the mods I included in the original design, a switchable emitter mod makes not sense when I tend to have it switched on 99% of the time and I'm unsure of whether or not I will include a switch for the tone circuit.

    Another important change in the new design is the schematic was hand numbered to correspond to the standard component numbering scheme of most big muff designs. Learn more about what I mean here: http://www.kitrae.net/music/music_big_muff.html

    Anyways expect a big update with a new PCB soon!!!!

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