Going Basic to Clone the Cornish P-2

Pete Cornish is a well-known pedal builder and designer out of the UK with an A-list of clients that includes the likes Brian May, Pete Townshend, and, one of my personal favorites, David Gilmour. All Cornish pedals are hand made in the UK to an extremely high standard, and are incredibly expensive. The subject of this build, the Cornish P-2, is essentially one of the ultimate evolutions of the Big Muff Pi circuit, and it runs for anywhere between $800-$1200 on Reverb depending on condition. I've seen new prices available from the Cornish website, but it is unclear how long the wait time is. As I mentioned in my entry on photoetching last month, I etched up several P-2 boards along with a couple of Cornish Bypass boards as well. I've managed to populate one board so far, and while I'm using a conventional bypass 3PDT daughterboard (from PCB Guitar Mania) for this first build I plan additional builds with the actual Cornish Bypass.

As I'd mentioned in January, the layout for this board came from the Effects Layouts blog. The site has tons of layouts in PDF form that can be transferred directly to your own copper board and etched to create your own PCB. As you can see from the photo above, I managed to get four boards and a couple of the bypass boards on one single sided sheet. For my first build I went ahead and soldered directly to the copper and then put an insulating clear coat over it to protect the PCB from corrosion. For future builds I'm tinning the PCB before assembly, but I may still use the clear insulating laquer.

For these initial experiments, I went ahead and just used my band saw to separate the boards. It works, but it isn't ideal for this application. I'm looking at getting a miniature circular saw with a blade designed for cutting PCBs. If that happens, I'll post more on it in a future entry.

Once the boards are separated then all of the holes need to be drilled so the components can be added. I do this with a Dremel and a pin vise bit. It takes a little while, but it seems to work pretty well. As you can see from the images above and below, the holes aren't perfectly regular like you'd see in a professionally produced PCB, but they get the job done. 

Once the board is drilled out, adding the components is just like using any other one-sided board. I've found it helpful to use copious amounts of liquid flux to help the solder flow and clear any oxidation from the surface of the PCB. For this particular build I went with mostly modern components. All of the resistors are 1% tolerance metal film (Yageo and KOA Speer). The capacitors are a mix of WIMA and Panasonic film capacitors. The P-2 uses 4148 diodes rather than the 1N914 you see in the regular BMP. Finding a small 5401 diode proved impossible, so I had to go with a larger 3W version. The circuit seems to work fine, but I think it's likely overkill. The P-2 also uses one BC549C and four MPSA18 transistors.

I've been extremely impressed with the Effects Layouts documentation and boards so far. The parts are all clearly labeled, and while challenging, it isn't impossible to essentially create your own pedal from scratch. Once the pedal was together, I went ahead and soldered in the potentiometers and tested the pedal using my "spaghetti" tester (below). I created this tester as part of my first Anasounds build, and it is incredibly useful for testing pedals before they're actually boxed.

Once I'd verified functionality, for the enclosure, I decided to go with an homage to the original's packaging. I have black enclosures for the conventional bypass versions and dark gray ones I intend to use for any with the Cornish bypass module.

As to the sound. First, I guess a caveat is in order. According to the Effects Layout blog, this PCB and build represents "what most people think is the Cornish P2." That being said, the sound is absolutely amazing. It takes all of the best features of the BMP, but gives it a lot more warmth. It also has more mids. The only issue is now I'm in a bit of a quandary. My Violet Ram's Head 2 build has sort of been living in the BMP slot on my board (at least temporarily replacing my original Gilmour build from last September, though that's still sitting next to it off the board), but I think I like this one just a bit better. Is it wrong to have two BMPs one one board????