Simple, but great, Muff Fuzz upgrade

[Mark Hammer]

JD Sleep has a project for an EHX Muff Fuzz clone: http://www.generalguitargadgets.com/index.php?option=com_content&task=view&id=93&Itemid=26

The stock discrete Muff Fuzz is essentially a 2-transistor circuit not that dissimilar from the Fuzz Face.  The original used 2N5133 transistors - nothing special.  The circuit JD shows employs 2N5088/5089.  I had one in the old days, and didn't find it inspiring enough to survive disassembly.  I still have most of the individual components sitting in drawers, and the little box itself, but felt no compunction to resurrect it.

Browsing through a binder of schematics the other day, I stumbled onto JD's drawing and thought "Hmm, there's no emitter cap to ground.  I wonder if there is more gain on tap than I'm accustomed to?".  So, I threw one together on perfboard, using JD's drawing and some "button-style" 2N5088s (hfe around 680-730), and decided to "improve" it.  I wired up a 5k pot in series with a 10uf cap, and wired that up in parallel with the 2k7 resistor shown.

YOWZA!  Big time woolly fuzz with lots of thick  chewy bottom.      While the stock Muff Fuzz is sort of like a Fuzz Face, unlike a Fuzz Face, it has a pair of clipping diodes on the output to punch things up.  So, not quite a Fuzz Face, and not quite a Big Muff with double clipping.  Certainly goosing the gain of Q2 with the added cap, however, starts to bring it closer in tone to a Big Muff in terms of overall sustain.  Sure sounds like a double clipper to me.

I noted two things to attend to.  First, I found that when the pot was set to zero ohms, the circuit was not especially stable, so I wired up a 220R fixed resistor in series with the pot to set the maximum gain (i.e., minimum resistance between the emitter and cap).  The other thing is that a 5k pot, while readily available, has a fair amount of its rotation doing absolutely diddley squat - the extra cap does nothing until the series resistance starts to drop below 2k7.  Best to stick a 4k7 resistor in parallel with the pot to make it a sort of 2k5 pot and more of the pot range useful. 

Feel free to experiment with different cap values, the same way that Dallas-Arbiter did (ground caps have been known to be various values from 33uf and less).  Make sure the + end of the cap is at the emitter side, and the - side goes to ground.

I also stuck a SWTC on the end of it, just after the clipping diodes.  Since it can get pretty hot with the added gain, the clipping can get sizzling, so some treble taming is useful here.  I used a 470R fixed resistor, 10k tone pot, and 2700pf cap to ground.  Does a nice job.  I'm pondering whether to swap that for a FY-2 midscoop just to see if I can make it sound "bigger".  I'll let you know when the experiment is done.  For now, this is an ultra-simple mod that will bring a whole lot more utility and flexibility to what is arguably the simplest distortion EHX ever made.

Here is the modded circuit:

[Gus]

Or you could take the gain and external bias section(R1, R2, C2) of this and sub it in for the 2.7K and go gated to smooth(bias control) with a gain control.

http://www.diystompboxes.com/pedals/gusFuzzFace.gif

Link to another forum some sound samples in the thread all four are the same fuzz.
http://www.prodigy-pro.com/diy/index.php?topic=32333.0

[John Lyons]

Cool stuff mark!
I'll have to try that out.

John

[Darth Bawl]

I know I'm digging up a really old a$$ thread, but I have to say this is really cool. Mark, thanks a lot for this mod!

I've been messing with this one on the breadboard for a week or two now  and really like the addition of the emitter cap. Right now I have a switch so you can choose whether to use the emitter cap or stock Muff Fuzz.  So it's sort of an OD/Fuzz switch.  Both modes have qualities I like. Makes for a versatile pedal (if I can ever finish tweaking it..).

I left out the gain pot and just put a value I liked with the guitar volume maxed, so I can just roll off from there. I like to keep the pots to a minimum!  I liked my results with a 4.7uf cap rather than 10uf or higher, but I might need to revisit that before I'm done.  Also I thought it sounded "fake" with LEDs. So far I like an asymmetrical combo.   

But the circuit, to me, is quite dark-sounding overall, especially on the stock "OD" mode.  I'm trying to brighten it up a bit, and I wasn't big on the results of lowering the input cap.

I've been messing with adding the SWTC2 (http://www.muzique.com/images/swtc2.gif) and have found a pretty good mix so far (100k tone, 500k volume, .0033uf cap), but I still have to turn up the amp's treble and presence a bit more than I'd like. It's not a big deal, but still a little dark, and I don't like to mess with my amp's settings too much once I find a spot I like.

Anyone ever try adding this "High Frequency Brightener" to an OD or Fuzz? http://3.bp.blogspot.com/_mgaBQf-Ljq0/TOpBc037r3I/AAAAAAAAAAU/p70hHiLq-z0/s1600/frequency-brighteners-effect-guitar-circuit-schematic-diagram.PNG

i was planning to try the smaller circuit.  Requires another transistor but looks simple enough. I have a ton of 3904s. I'm going to try it tonight if I have time. If it doesn't work out, i'll probably just see if I can get the SWTC2 going any better, compare it to my other fuzzes, etc.  I am already happy with this mod and can live with turning up the amp's treble.

Thanks again for all the great stuff you share! 

[Darth Bawl]

I'm trying not to use the BMP tone stack in this one, because I used that in the last one I did (colorsound one-knob fuzz) so I'm trying to learn something new. lol but I'm starting to think the BMP tone stack might sound pretty good on this unit, so I might have to give that a try if this "Brightener" doesn't work out.

[runmikeyrun]

this is a cool idea, wonder if it could be applied to any transistor fuzz pedal?  To me, it reminds me of cathode bypass caps on tube amps increasing gain and bass.

[Mark Hammer]

this is a cool idea, wonder if it could be applied to any transistor fuzz pedal?  To me, it reminds me of cathode bypass caps on tube amps increasing gain and bass.

That's precisely where I got it from.  Thanks to JC Maillet and the amp book of his.

And yes, the value of the bypass cap determines where the gain is applied.  Think of it a bit like manner in which changing the .047uf cap on a Tube Screamer changes the bass rolloff, and how much gain is applied mids compared to lows.

A second experiment. that I've posted elsewhere here, is to connect the wiper of whatever gain pot you're going to use to the emitter of that transistor, and run a different-value cap to ground from each outside lug.  Let's say you use a 5k-10k linear pot.  At mid-position, with a path approximately equal to the 2k7 emitter resistor, the pot offers no addition bypass for any portion of the spectrum, so no gain.  As you rotate in either direction, you provide a more efficient path to ground for whatever frequency content passes through the cap efficiently, and more gain.  meanwhile, the resistance on the other leg of the pot increases, having no impact on transistor gain.

Technically, one can use a much larger cap value on the one leg than the other, such that you get full-spectrum boost in one direction, and treble boost in the other.  Because there is much less signal living in the top end, the treble-boost will be noted primarily in the form of a brightening, and much less in the form of increased distortion.

[WGTP]

Nice stuff Mark.  I think Joe used a cap blend in that location on some of his stuff.  It reminded me of some of Tim's stuff at the bottom of the page.   http://www.oocities.org/tpe123/folkurban/fuzz/fuzzyfaces.html

I have wondered about using a single diode after a fuzz face since it produces asymmetrical harmonics. 

[DaveBasser]

Thanks for this, Mark.  I really like it for bass. 

Can anyone tell me what C1 is doing?  I'm not hearing much while it's on the breadboard.

[digi2t]

Thanks for this, Mark.  I really like it for bass. 

Can anyone tell me what C1 is doing?  I'm not hearing much while it's on the breadboard.

Power filter I believe.

[Mark Hammer]

You can hear what the mods do here: http://www.youtube.com/watch?v=npxq2DSAyuk&list=HL1334013850&feature=mh_lolz

[digi2t]

You can hear what the mods do here: http://www.youtube.com/watch?v=npxq2DSAyuk&list=HL1334013850&feature=mh_lolz

I just watched the video Mark...



Amazing tone, and super versatile to boot. Can you shoot me the schematic of the "as built" in the video? I'd like to do a vero of this one. Well worth it IMHO, just covers an enormous amount of tonal ground. Bravo... eh!

Cheers,
Dino

[Gus]

I don't think it sounds good.

Edit I think what I posted sounds harsh
I think samples of effects, amps, microphones, speakers are a tricky thing to record well.  There is the room the amp the microphone the computer speaker that if will often be used the distance and height of the microphone placement etc.  Marks circuit might sound very good.

[Mark Hammer]

Welcome to the world of distortion, eh? where one person's "It cost me $500, but it was worth every penny" is another person's "I paid $60, but was happy to see it go for $20".

Do consider that it's an LM380-based amp into a 6" speaker, and recorded with a cheap electret optimized for picking up sibilants from across a lecture hall.  It may sound better in real-world conditions than what you're hearing.

[Gus]

Yes I think a different amp would make a difference, I should have put that in my post.  IMO fuzzes often sound the best with a turned up tube amp.

[deadastronaut]

most fuzz'z sound nasty to me anyway ....but thats the point isn't it?...i don't really know whats good or not as i'm not a fuzz fan though!...one mans...is one mans etc etc...

ok, i'll get my coat...

[DougH]

Re. the original post- Part of what you are doing with the bypass cap Mark, is canceling (grounding, actually) some/all of the negative feedback going through the 100k feedback resistor, in addition to canceling the degenerative feedback from the emitter. This is part of the reason for the dramatic increase in gain, and also part of the reason for the instability without a small resistance in series.

[DougH]

Welcome to the world of distortion, eh? where one person's "It cost me $500, but it was worth every penny" is another person's "I paid $60, but was happy to see it go for $20".

Do consider that it's an LM380-based amp into a 6" speaker, and recorded with a cheap electret optimized for picking up sibilants from across a lecture hall.  It may sound better in real-world conditions than what you're hearing.

I think it sounds pretty good. I preferred some settings over others but overall I thought it was a good demo of the sounds available.

Two mics, one on the speaker and one in the room- panned left and right in the mix can add some ambience:

http://www.youtube.com/watch?v=Rd_IkHvcNXA

But I've done a lot of single-mic recordings that sound pretty good too and I think Mark's recording sounds fine, esp considering it's a 6" speaker and electret. I'd rather hear that than a fuzz box DI'ed into the soundcard recording.