Electro Harmonix Op Amp Big Muff and another Lovepedal Purple Plexi 800
Hey everyone. After a crazy few months of starting a new job I’m finally back to building pedals. Today we’re going to look at one of my favourite variations of the Big Muff as well as my (current) favourite Marshall-in-a-box pedals with a few surprises along the way.
I think the Op Amp Big Muff is my favourite because of its uniqueness. Instead of the usual 4 transistors this version features two small IC chips. Well how does that affect the sound you ask? Personally I think it provides the muff with a bit more gain and mids, both of which are wanted in my opinion. I built this pedal almost a year ago, but I thought I’d like to revisit it as I recently found out that the Op Amp muff was used by Billy Corgan on the Smashing Pumpkins’ album Siamese Dream. Here’s what mine turned out to look like:
I stole that graphic from a Middles Ages textbook that I have kicking around for some odd reason. The uneven surface texture on the enclosure is a result of a brass brush on a dremel, and the font is the same font used on older Big Muffs. It all makes the pedal look somewhat “Doomy” but I like it.
You’ll also notice a little toggle switch near the top of the pedal. That’s the tone-bypass switch, which was a stock feature on the 1978 Muff. Basically it takes the tone control circuit out of the pedal and provides you with a less-fizzy more middy sounding muff, which I find cuts through the mix of a band.
On to the PP800. I built this for a friend in Montreal. He requested a modification to enhance the bass response. Going back to my training in pedal-building 101 I experimented with changing the value of the input capacitor to fine-tune the amount of bass response I was able to get two values that really work both for single coils and for humbuckers. Here’s a few pics of the completed build.
The enclosure looks much more purple in person. After using a very nice DSLR at work I’ve decided to upgrade from a crappy cell phone camera to something more legit. If you have any camera recommendations please let me know!
I finished the pedal with Silver Marshall knobs and a frosted white LED.
Finally, here’s a a little tip when building a PP800. I’ve noticed that quite a few people’s clones have a very annoying high pitched squeal when the gain is turned up to 11. My solution to this problem is to replace the 10R resistor connected to lug 3 of the gain pot with one of a slightly higher value. I use a 47R resistor in its place and I get none of that squeal, even at higher gain and volume settings.
Next up will be a pair of KLONES and a Tube Screamer of some sort. Stay tuned!
Woody Laboratories 
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