Fractal Audio DRIVE models: Pi Fuzz (based on Electro-Harmonix Big Muff Pi)

Muad'zin said:
Muffs usually sound fine wherever you place them in a pedal chain. It's a very forgiving circuit. The Pete Cornish G2 even has two buffers in series in front of it (buffered bypass and input buffer). It's the more primitive 60's fuzzes that are so finicky that they have to be first in he chain. Or worry about having the right biased transistors. You can basically throw everything into a Muff circuit. And they have, that's why there are so many variants.

I love the Muff. I've basically built every version there was based on the Kitrae schematics. But not at first though. The one thing a Muff needs is more mids. It's scooped tone stack has a tendency to make you disappear into a mix if you don't add some mids somewhere in your signal chain. If you have a Muff pedal, especially with those big EHX boxes, the easiest mod to do this with is add a Skreddy style midswitch. Take a DPDT on/off/on switch. Wire one center lug to the collector of the third transistor, the other center lug to lug 3 of the tone pot. solder a 4n7 capacitor to the top two lugs of the switch and a 10n capacitor to the bottom two lugs. What it does it will place an extra capacitor in parallel to the Big Muff tone stack. Center setting of the switch will be stock scooped tone, bottom setting (4n7) flat mids and top (10) boosted mids. Usually the flat setting is enough to suddenly emerge in a bandmix. I've experienced this in rehearsal where I couldn't hear myself, switched from scooped to flat and BAM! There I was.
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If you want to replicate the flat mids setting on the axe set mid frequency at 1350 Hz and Mids at +4.5 dB ;)
 
Is there anything I can do to get this to sound closer to the Russian circuit? (Namely the new RI I don't want to buy but I'm still considering anyway...)
 
Maybe add some EQ after it? And don't turn it up on full as Russian Muffs were said to have a little less gain. Check the Kitrae site for the characteristics.
 
yek said:
Fuzz was one of the first “transistorized” guitar effects. Transistors amplify the signal and when they clip, distortion is generated. When the clipping is hard instead of gradual, the distortion is harsh and buzzy, named “fuzz”. The tone of fuzz depends greatly on the type of transistor used: germanium, silicon etc. (available as Clip Types in the Drive block).
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I have a problem with this description as applied to the Pi. Everything in it is true - when you're talking about an actual fuzz circuit. But the Big Muff Pi, isn't a fuzz design. Yeah, it has a big, woolly distorted sound, but the circuit isn't anything like a Fuzz at all.

First off, the Pi uses diodes for clipping. So the, "and when they clip, distortion is generated", is irrelevant. The Pi does use cascading gain stages, but this is just to pile clipping on top of clipping.

As far as I know, the Pi has always used silicon BJT transistors. Common as dirt and no big deal, and the exact model isn't considered to be a big contributor to the tone or nature of the clipping. In the 70's I did own an opamp version of the Pi (which used a chip to provide the amplification to drive the clipping diodes), so even EHX didn't considered the transistors to be a vital part of the sound. The opamp version, however, really was nowhere near as good as the transistor version.

So the "The tone of fuzz depends greatly on the type of transistor used: germanium, silicon etc. ", doesn't really apply here. Big Muffs never used germanium transistors.

Finally, "(available as Clip Types in the Drive block)", is probably not correct either. I'm not sure how Cliff translates the "clip type" parameter with the FF design drive blocks, but I'm fairly certain this is going to refer to the clipping diodes for the Pi model. The actual Big Muff uses silicon diodes.

I'll admit that calling a BMP a "fuzz" is one of my personal hot buttons. To me, it doesn't sound anything like a real fuzz, and I don't see why you'd lump it in with them. Under the hood, though, it's clear that fuzz and BMP have NOTHING in common. Nothing. Nothing. In truth, the BMP is a unique design using discrete transistors with diodes in a feedback loop, and then running two of those clipping circuits back-to-back. So I think it deserves to go in a category all its own.

All of that is just a rant, but when you take that misconception and apply it to a description of the circuit to explain how it's modeled in the Axe, what you end up with is erroneous.
 
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StickMan said:
I'll admit that calling a BMP a "fuzz" is one of my personal hot buttons.
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No kidding.

To me, it doesn't sound anything like a real fuzz, and I don't see why you'd lump it in with them.
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Because the world at-large classifies the BMP as a "fuzz pedal". It's literally on the wikipedia page as an archetype for the category.

Big Muffs never used germanium transistors.
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Well, EHX sells a BMP Germanium version right now. Germanium mods for the BMP have been common since its inception.

Under the hood, though, it's clear that fuzz and BMP have NOTHING in common. Nothing. Nothing. In truth, the BMP is a unique design using discrete transistors with diodes in a feedback loop, and then running two of those clipping circuits back-to-back. So I think it deserves to go in a category all its own.
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The classification has absolutely nothing to do with the circuit and the components used in the circuit. It's entirely based on the sound of the pedal. Across the spectrum of pedals classified as "fuzz" pedals a range of clipping methods and circuit topologies can be found, the BMP being one of them.

All of that is just a rant, but when you take that misconception and apply it to a description of the circuit to explain how it's modeled in the Axe, what you end up with is erroneous.
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I vehemently disagree with this. As I said before, the world at-large considers the BMP to be a "fuzz" pedal because it isn't trying to be amp-like in its distortion characteristics. The classification in the Fractal world is in complete alignment with the real world classification.
 
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iaresee said:
I vehemently disagree with this. As I said before, the world at-large considers the BMP to be a "fuzz" pedal because it isn't trying to be amp-like in its distortion characteristics. The classification in the Fractal world is in complete alignment with the real world classification.
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It's an objective fact that the paragraph I quoted from the OP is erroneous. It's description of how fuzz circuits work is totally inapplicable to the BMP, and doesn't belong in an entry about the BMP. So I'll stand by what I said, "when you take that misconception and apply it to a description of the circuit to explain how it's modeled in the Axe, what you end up with is erroneous."

And please, don't get me started on the imaginary difference between "distortion" and "overdrive".
 
iaresee said:
Across the spectrum of pedals classified as "fuzz" pedals a range of clipping methods and circuit topologies can be found, the BMP being one of them..
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There's a family of drives that are based on the FF circuit (Tonebender, Rangemaster, Fuzz Face, and so on), and there's the BMP (and all of it's clones/derivatives). Name one other, please.
 
Hi StickMan,

I welcome all suggestions for improvements and corrections. As I write in the PDF guide version of these threads: "there WILL be mistakes".

While the statement at the beginning of the OP about fuzz boxes is correct by itself, you may be right when applied to the BMP. TBH I don't know and I can't tell. I have no reason to doubt your statements, so readers can take your post in this thread into account.

But, like Ian, I estimate that 99% of guitar players out there call the Big Muff a fuzz. As a matter of fact, even the Axe-Fx II's manual calls the BMP a fuzz. Whether the BMP's internal circuit justifies that label or not, is not important (to me). A quest to change the perception of the BMP as a fuzz, reminds me of Don Quixote. :)
 
StickMan said:
There's a family of drives that are based on the FF circuit (Tonebender, Rangemaster, Fuzz Face, and so on), and there's the BMP (and all of it's clones/derivatives). Name one other, please.
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Your bucketing is far too narrow. There are other topologies that fall into the fuzz category as well. Fender Blender/Shin-Ei Superfuzz, Percolator, Bosstone and even the SHO. All fuzzes in their own right and their own unique topologies. Fuzz is a fuzz because someone thinks it's a fuzzy sounding pedal; not because it's based off some specific circuit.

If you want to take this some place more appropriate, say https://diystompboxes.com/, I'm sure it'd be interesting.
 
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StickMan said:
As far as I know, the Pi has always used silicon BJT transistors. Common as dirt and no big deal, and the exact model isn't considered to be a big contributor to the tone or nature of the clipping. In the 70's I did own an opamp version of the Pi (which used a chip to provide the amplification to drive the clipping diodes), so even EHX didn't considered the transistors to be a vital part of the sound.
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If that's the case then why are Muffs with the 2N5133 transistors so highly valued? Do transistors matter in the Muff? I've built dozens of them and I can't really say that there's much of a difference if you swap out different sets, except that BC550C's are a little less noisy. But then again to me 99.9% of all overdrive pedals sound the same and the Muff master Skreddy seems to think they do matter. And I do like his Muff versions a LOT.

The opamp version, however, really was nowhere near as good as the transistor version.
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Go wash your filthy mouth! :p The opamp Muff is AWESOME!!! Different, yet awesome in its own right.
 
Here's something I came across:

Use a clean amp model, add an overdrive with low gain, then add the PI Fuzz with Tone turned up a bit. Crushing wall of sound.
 
Did you guys managed to get convincing Big Muff tones from the 90's bands like Nirvana/Smashing Pumpkins/etc. in Fractal land?
 
I finally found a realistic setting for 80’s Big Muff Deluxe (one of the holy grail muffs), which I matched to a real recording. It cleans up so good with volume knob: 1-2 clean, 3-6 fuzzy overdrive, 7-10 ripping fuzz. I was actually chasing the fuzzy overdrive sound, and it turned out other sounds were amazing as well. I mainly use the bridge pickup (high output), as neck pickup can get quite fuzzy.

As I said I mainly use the fuzzy overdrive setting, and when I want a mountain top lead I crank up the guitar volume. You can stack a Tube Screamer or another overdrive pedal after the fuzz if you want more gain. I used to have a hard time trying to stack other pedals with the PI Fuzz model, but with this setting it works wonderfully. Add a delay and you’re good to go. I use the Digital Vintage in front of the amp with a few tweaks. The sound I was trying to replicate also uses an octave down octaver with low mix, so try that as well in front of the fuzz.

Use an overdriven amp like Marshall JCM800 or JMP. I use a JCM800 with a self-made matching G12T75 impulse. Keep the sustain (Drive) low and at already around 1 the fuzz character starts to change, which is not right for this particular sound. If it’s not bright enough, add some tone and vice versa. There’s plenty of gain even though Drive is at 0, so don’t worry.

Type: Pi Fuzz
Drive: 0
Tone 6.5
Volume: 9-10
Mix: 87 %
Low cut: 300 hz
Bass: 7
Diode: OP-AMP
Bias: -0.450
Add some middle frequencies if you feel like there’s not enough

I haven’t yet tried this against my real Big Muff Deluxe, but I kind of don’t feel like doing that. The real one is so noisy and the settings already match 100% with the record I was trying to replicate where I know a Big Muff Deluxe was used. I couldn’t be happier, thanks yet again Fractal ❤️
 
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