PedalBuilder
Well-known member
Continuing my Big Muff building bonanza, here's my take on the Emanating Fist Electronics XB-70. The XB-70 is essentially the same circuit as this 1976 V3 Big Muff that Kit Rae traced, but with a R11 in the below schematic changed to 10k:
It was a nice, straightforward build with no unobtanium parts. I used one of my Big Muff boards. I designed them to use parallel silver mica capacitors for the base-collector capacitors; I opted to use C0G ceramic capacitors for this build, so the parallel capacitor footprints were left unpopulaed. The transistors are BC549C and 2N5088, with hFE between 525 and 550. I had to make a few part substitutions—I didn't have a 430k resistor for the output stage, so I used a 750k resistor with a 1M resistor tacked onto the back in parallel, which measured out as exactly 430k (not that this kind of circuit calls for that level of precision, but hey, I'll take it). I didn't have a 3nF capacitor, so I used a 2.2nF box film cap on top, with a parallel 820pF ceramic cap tacked onto the back. The Volume and sustain knobs are these ones from @Amplified Parts. Everything else is the whatever happened to be the cheapest on Tayda.
David Main describes the XB-70 as sounding "like torn leather soaked in piss and salt smushed lovingly into ears... It is a brute of a pedal, has a really intense roar at full tilt, like any good Big Muff really." I'm not sure what most of that meant, but I agree that it definitely sounds like a Big Muff. (You should give it a try, @Guardians of the analog, you might like it!) It has a bit more midrange than a Ram's Head, but still has the classic Big Muff compression and mid-scoop. There's some more complexity to the distortion than most Big Muffs, possibly because of the mismatched collector resistors on the clipping stages. And yes, it definitely dooms. Anyway, it's a Muff that's well worth building and a good one to add to the collection. It'll definitely get some use. Go get yourself a Muffin Fuzz PCB and build one if you haven't done so already.
It was a nice, straightforward build with no unobtanium parts. I used one of my Big Muff boards. I designed them to use parallel silver mica capacitors for the base-collector capacitors; I opted to use C0G ceramic capacitors for this build, so the parallel capacitor footprints were left unpopulaed. The transistors are BC549C and 2N5088, with hFE between 525 and 550. I had to make a few part substitutions—I didn't have a 430k resistor for the output stage, so I used a 750k resistor with a 1M resistor tacked onto the back in parallel, which measured out as exactly 430k (not that this kind of circuit calls for that level of precision, but hey, I'll take it). I didn't have a 3nF capacitor, so I used a 2.2nF box film cap on top, with a parallel 820pF ceramic cap tacked onto the back. The Volume and sustain knobs are these ones from @Amplified Parts. Everything else is the whatever happened to be the cheapest on Tayda.
David Main describes the XB-70 as sounding "like torn leather soaked in piss and salt smushed lovingly into ears... It is a brute of a pedal, has a really intense roar at full tilt, like any good Big Muff really." I'm not sure what most of that meant, but I agree that it definitely sounds like a Big Muff. (You should give it a try, @Guardians of the analog, you might like it!) It has a bit more midrange than a Ram's Head, but still has the classic Big Muff compression and mid-scoop. There's some more complexity to the distortion than most Big Muffs, possibly because of the mismatched collector resistors on the clipping stages. And yes, it definitely dooms. Anyway, it's a Muff that's well worth building and a good one to add to the collection. It'll definitely get some use. Go get yourself a Muffin Fuzz PCB and build one if you haven't done so already.
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