This is the continuing progress of the Big Muff Pi (David Gilmour circuit) effects pedal. In the previous blog, I thought I'd give you a back story and a potted history around the Big Muff how David Gilmour started using it and also the variability of these pedals, but now I want to get into the building of this pedal proper. I now have all the components except the enclosures (I'll buy them later once the boards have been built and tested) so now all is to be done is etching the boards.
To recap the circuit is based on a schematic that was traced from a pedal that was tested by Kit Rae, in which he identified this particular circuit as the closest in his opinion to the one that has been used by David Gilmour of Pink Floyd from around 1976/7 to the present day. I'm interested in what this sounds like and can't wait to hear it. Apparently this is similar to the Pete Cornish P-1 Custom Fuzz which was Pete's variation of the the Big Muff circuit but with enhancements. we don't know what the circuit is like in the P-1 as it's sealed by Pete Cornish to prevent nosy people stealing his circuit layout. But what we do know is it's heavily based on the Big Muff, and was designed at the time to be an alternative to the EHX Big Muff which David was using at the time. Therefore the sound of the P-1 was designed to be as close to Davids Big Muff as possible.
Both boards have been etched, and now starts the laborious task of drilling the holes........ I hate drilling the holes, as I'm doing them by hand. I need to invest in a Dremel and a stand to speed the process up. Following the etching process you can see that there are some tracks on one of the PCB's that has some breaks on it. In this case I'll bridge them with solder and/or some spare leads that I saved from previous builds. On all my builds I save the off cut component leads. These come in really useful for extending terminals (like on the pot terminals for the power boost), also they're invaluable for repairing broken tracks as in this case. Hopefully i'll be able to just bridge with a little solder, but if the gap is too much, I'll solder in some wire to bridge the gap. Either way, It's an easy fix.
EDIT - 11th Nov 2017: It's now quite a few weeks since the above paragraph was written (I've been ill, as well as other family orientated issues), and I've decided to buy pre-fabricated PC boards. I just wasn't happy with those boards I etched, too many breaks and the tracks looked iffy. They just looked unprofessional and i'm presenting one of these to a professional musician so I want to ensure they look right not only on the outside, but on the inside too. Attention to detail with these pedals is key, and although the pedal I'm giving him will be set up to only use a 9vDC power supply, so he'll likely never open the case up as he won't be changing batteries.... I'll know it's not right. I suppose it's the perfectionist in me coming out
So the boards I'm using are supplied by a company called Pigeon FX. They not only make their own vintage pedals like I do, but they also have vintage design boards fabricated exactly the same as the originals, so this is what I intend to use for these builds. Also, the holes are pre-drilled so that saves me that headache. These boards are available on EBay, for a not unreasonable price... As soon as the boards arrive, which hopefully will be in the next day or two i can then start immediately populating the boards. What i'll likely do is populate one board, test it then use that as a template to populate the second board. Work in progress photos to follow 
EDIT - 10th Dec 2017: On wards and upwards. I have some photos to share since I bought the pre-fabricated PCB's. These PCB's are brilliant and are so easy to solder onto. If i do say so myself, my soldering has reached new heights below is a photo of both boards which i'm soldering at the same time, so they're both at the same stage. One thing I will say about these boards is they're considerably bigger than I expected. When I etched my own boards, i used the pin spacing of the potentiometers to size the board and the 1/4w resistors were perfectly sized for that size board.... However, with the pre-fabricated boards 1/2w would have been a better choice size wise, but hey, i'm not too bothered.
I have however, hit upon a problem sourcing some ceramic capacitors. I've ordered a number of 50v caps off ebay and to date the caps that are delivered are physically too small. They will work, but they won't look aesthetically correct on the board. The caps I have here have about a 2 or 3mm pitch between the pins, where it needs to be around 8mm. the size of the capacitor ideally needs to be around the same size as the resistor so it at least look nice. If I was building these for myself (one of them is for me) i wouldn't worry, but one of these is for a professional musician so attention to detail is high. Can people look to see if you have any lying around?
These capacitors are way too small!!!
The capacitor values i'm after are:
4 off 470pf
2 off 0.004uf
2 off 0.012uf
The 0.012uf is an odd one, and i can't seem to find that value anywhere, the nearest i can find is 0.010uf which will probably work fine, but i'm trying to ensure that the values are as authentic to the original as possible. Also I've learned that the capacitor values do have an effect on the end result. To this end I've decided to use 0.01uf I don't really think the 0.002 will make that much difference.
EDIT - 10th July 2018: I've been really busy, and have had commissions for this pedal, so consequently have been slack in updates. So here are the final blog posts for this pedal. Other than building one for myself, I was also building one for a friend. After delivering this pedal to him he posted something on Facebook regarding the pedal and I was asked to build one for a guy in Austin Texas which has since been sold for boutique pedal money!! I've also has interest from a guy that roadies for a named band, and also from the guitarist from this same band regarding an endorsement deal. So it looks like I'm getting into small production for this pedal. The reason I believe, is people are constantly chasing David Gilmours guitar tone, and this pedal is as far as I know the only one on the market that gets close to his pedal, and for a fairly reasonable amount of money.
I managed to get components that are at last the right size, so they don't look stupid on a big board like this, and here's the end result. The blue and yellow caps are the only compromise as they're brand new, and not NOS.
Fully populated board, now it was time to design the enclosure to put it in. For this I used some poetic licence for my own pedal, and copied the Big Muff logo, however for the one i built for the client in Austin TX i designed my own decal, calling it "The Gilmour". Replacing the EHX Rams Head logo with a flying pig in homage to the Pink Floyd flying pig on the Animals LP cover.
| original pedal built for myself. This is based on the original Big Muff pedal design, including the Rams Head logo in the bottom right corner. this pedal was given to my friend as a present. mine is exactly the same, except I have black knobs on mine, not red. | This is the revised pedal design, using a more Pink Floyd theme. I really like this theme, and have managed to use the same font as used on the Pink Floyd Animals LP cover. Both pedal have a blue water clear LED that lights when the pedal is engaged. |
|---|---|
 |  |
Verdict........ This pedal kicks some serious bottom! The sustain is never ending, and the sound is huuuuuge. I will get a video demo up of this as soon as I can, as I'm getting people asking me for video clips as they're interested in buying one. So i really need to do a video. once again sorry for the slackness in updates, and I hope you've all found this interesting.
The next 3 or 4 pedal builds are already in the pipe line..... look for forthcoming blog posts regarding he Black Russian Big Muff, MXR Micro Amp, An Electric Mistress clone called a Current Lover, and a special blog post about an original EHX Electric Mistress PCB that I have acquired and hope to breathe life into.
Top Comments