Finally a True "Steggo" BMP Clone!

Any long time readers of this blog will know that I really like the Electro-Harmonix Big Muff Pi in all of its forms. It is one of the main pedals of choice for some of my favorite guitarists, including David Gilmour, and is a key ingredient in their overall sound. I've built several BMP clones over the years, but all of them have had enclosures that mirrored the original in one way or another. Recently I've tried to do a "make over" of any of my "Steggo" pedals with a focus primarily on creating fun dinosaur names for them, and I've finally come up with a dinosaur themed BMP clone!

With the Russian invasion of Ukraine, there have been several people in the pedal building community working to find ways to do their bit to help. I'd previously built the Ukrainian BMP that I donated to Pedals for Ukraine. I also built a Blues Driver Galaxie Mod (the Riabininohadros) that was a more dino themed pedal that also raised money for Ukraine. I've recently posted build logs of my new Klon KTR clone and Brian May Treble Booster based on boards designed by South Obolon FX - boards he made Gerber files available for free - asking only for a donation to Ukraine's fight against Russia. He also posted some designs provided by LoudCancer with the same ask - which I was more than happy to do!

One of the boards posted was a Big Muff Pi board. As it is one of my favorite pedals, I had some made up and proceeded to go crazy! This particular build is very similar to some of my early builds in that it is a '73 Gilmour (using the AionFX Halo excel sheet as a guide). This particular one uses vintage Allen Bradley carbon resistors. The capacitors are a mix of panasonic film and some ceramics. The transistors are vintage 2N5133. The diodes are also vintage 1N914s. Once getting the board together, I attached the pots and ran a quick test - which is where I found one problem with the board - the potentiometers are set up backwards.

I double checked to make sure I hadn't soldered them to the board incorrectly, but no, they were right. I then checked the circuit diagram, and all three potentiometers are reversed on the diagram. So while the board is a correct translation of the diagram, the problem was at the circuit diagram. I simply reversed all three and now the pedal works perfectly.

The wiring follows my normal process using a daughter board for the 3PDT footswitch. I'm also running a star ground to the input. I did have to flip the Switchcraft jacks to ensure they fit above the board (as the board is a little higher than I'd like because of the reversed pots). I also decided to go ahead and add the battery snap since all of my BMP enclosures are set up to accept one, and this is an old school pedal.

So I promised a dinosaur, and here he is! The Muttaburrasaurus - that's right, it's the Big Mutt Phi pedal! According to Wikipedia:

"Muttaburrasaurus was a genus of herbivorous iguanodontian ornithopod dinosaur, which lived in what is now northeastern Australia sometime between 110 and 103 million years ago during the early Cretaceous period."

Given the Greek letter reference, I went hunting for a suitable background for Mutt to inhabit. I found an old painting in the public domain - Religious Ceremony in Ancient Greece by Francis Oliver Finch from 1835. At this point I'm using actual EHX knobs, but I may change them out at some point.

As to the sound - it is a little bit of a mixed bag. Because of the Allen Bradley carbon resistors, the noise floor is fairly high, but the sound is unmistakably BMP. On its own with a noise gate, the noise floor is easily dealt with, but if you add boost pedals or other effects, the noise is a bit higher than I'd like. I'm planning on making up a 100% modern pedal with the same values (though I may still use vintage transistors - or at least modern transistors with similar gain as the vintage ones) to see if I can bring the noise floor down.