PETE CORNISH: P-2

It has now been traced by Aion FX - updated layout can be found here.

The Pete Cornish P-2  is somewhat of a mystery as it's never been traced, so all information is gleamed and guessed from various sources.  It seems that no one, including myself, wants to pay top dollar to de-goop what we all know is some kind of Big Muff. 

So what do we know?

• it uses the same PCB as the G-2 (photos here)
• silicon diodes
• double buffered
• the tone control is a low-pass filter, not a standard BMP tone stack (description here, listen here)
• reportedly first made in the eighties, before Big Muffs from the former Soviet Union appeared on the market in the nineties

So this leaves the P-2 reasonably open to interpretation in many regards, but there are parameters to work within that will get you in the general area regarding sound.  Pete Cornish was working with David Gilmour, who liked Rams Head Big Muffs.  Kit Rae describes the V2 1973 #3 Rams Head Big Muff as the closest sounding to the tones Gilmour produced and very similar to the P-1.

Kit Rae sound comparisons below - to my ears, the P-1 and P-2 sound very similar in gain/clipping; the main difference seems to be the tone control.

P-1, P-2 and G-2 chords

P-1, P-2 and G-2 tone pot sweep

To make things a little more interesting/confusing, here's a gut shot from an early Pete Cornish pedal before he started gooping circuits and including double buffers.  They're calling it a P-2, but I think it might be an old P fuzz - who knows...  The board is laid out the same as the G-2, but you can see 2 x capacitors in the tone section instead of just the one - so this seems to have a traditional BMP tone stack.  There are also a lot of 220n MKT caps visible, following the same pattern as the G-2.  

PROBABLY NOT A P-2, BUT MAYBE IT'S CLOSE ENOUGH VERO LAYOUT

This is how I built my P-2, which is 100% guaranteed to not be an actual P-2...  but it will get you in the same area.  It has plenty of gain on tap; it could perhaps even do with a little less - maybe increase the emitter resistors a little.   

Update:  I did reduce the gain structure a little by increasing the emitter resistors and decreasing the collector resistor on the last clipping stage.  Not a massive difference, really.  Subtle, yes; game-changing, no.

Please remember that the tone control is a low pass filter; setting it to the centre like a typical Big Muff is not the best place to start.  Start with it open, then roll it back to tame the highs.  Don't forget to put the Cornish buffer in front of this too.   

Layout removed, as values have now been confirmed (I was pretty close)

ON THE SCOPE / FFT

Signal:  440hz sine wave, approx 130mv TRMS

 

Boost stage, Sustain 100%

First clipping stage, Sustain 100%

  

 

 Second clipping stage, Sustain 100%