Fuzz Face Questions

[fuzz guy]

I just built a "Roger Mayer" germanium Fuzz Face from a kit.  It's identical to this schematic, except in place of the 18k resistor there's a 47k trimpot for setting the bias. I used 2N404 cans and found I liked it biased at 5.5v.



It's actually the first FF I've ever owned, so I'm not that familiar with the idiosyncrasies of the circuit. I do know that most tend to set theirs with the Fuzz knob pretty much all the way up, and I can see why. All the best sounds are right there in the last few millimeters of travel. Mine has a 2kB pot, is it possible to change the pot value or taper to open up the usable range?

I've also always read about all the great sounds you get by rolling back the guitar's volume, and they are there, but the sound is on the bright side when the fuzz knob is all the way up. Turning down the Fuzz control does remove a bit of the high end, but as I mentioned above there's not much space to work in.

So are these issues just part of the whole Fuzz Face experience or has anyone found some mods to get around them?

[GibsonGM]

One thing you could try is remove the gain pot...place a 1k resistor where the 2k pot is...run it to a 1k pot with its bypass cap (so you are just inserting a 1K resistor between a 1k pot and that 100k resistor/Q2 emitter).    By replacing the 2k pot with a 1k, you will have much more 'room' in its sweep to dial in your sweet spots.  The higher pot value is compressing that range.   Of course, you could add that resistor to the 'upper leg' of the pot quite easily by desoldering 1 wire.

Another way to do it is to use a 1.5k resistor and a 470 ohm pot, for MORE control over that small range.   Very common idiosyncrasy with FF's! 

I've never bothered to try to tame the 'turned down pot treble boost'; always felt it would affect the cranked tone too much, and make it darker. 

HTH, welcome to the forum!

[antonis]

One thing you could try is remove the gain pot...place a 1k resistor where the 2k pot is...run it to a 1k pot with its bypass cap (so you are just inserting a 1K resistor between a 1k pot and that 100k resistor/Q2 emitter).

Shouldn't that narrow NFB gain margins, Sir..??

[GibsonGM]

One thing you could try is remove the gain pot...place a 1k resistor where the 2k pot is...run it to a 1k pot with its bypass cap (so you are just inserting a 1K resistor between a 1k pot and that 100k resistor/Q2 emitter).

Shouldn't that narrow NFB gain margins, Sir..??

How?  I'm only suggesting that he use a smaller pot w/fixed resistance in the same place the pot would be....I will make a picture to be more clear.

THIS should be a simple way to improve the range of the 2k pot, would it not?  And will not affect NFB or anything.

Modified per suggestion of Duck Arse below!!

[antonis]

You've now made it clear, Sir..!!! 

[GibsonGM]

A picture is always easier!!

[duck_arse]

yeah, but, Sir Mike - he now only has the bottom half of the fuzz range, 0-5 instead of 5-11. the 1k fixxed should go between pot bot [CCW] and ground. cap stays between wiper and ground, thus bypassing the fixxe 1k at all times.

[GibsonGM]

yeah, but, Sir Mike - he now only has the bottom half of the fuzz range, 0-5 instead of 5-11. the 1k fixxed should go between pot bot [CCW] and ground. cap stays between wiper and ground, thus bypassing the fixxe 1k at all times.

EEEEEEEE  ha ha, you're right!  Hang on, I'll fix it.      I swear, it's easier to just DO than draw or explain, that is where I tend to get in trouble.

**Fixed**

[pinkjimiphoton]

as a fuzzmonger thats focus is really only on fuzzface and variants,
a few suggestions.

ditch the 2k pot. it doesn't help do anything but make the circuit more unstable.

use a C1k fuzz pot. an A1k will work almost as well, but really needs to be set up "backwards" to be useful.
the 2k pot spreads out the gain more, sorta, but not in any particularly useful way.

it was added by mayer <he's on facebook and responds to questions, btw> at the request of hendrix, who was looking for more volume out of his fuzzface.

the earlier ge  ones sometimes barely were above unity gain at some temperatures. the smaller the e resistor, the more gain you'll get. a directly grounded emitter will have more gain than a bypassed one, and for all intents the second stage is a bypassed emitter resistor. as you turn it "up" the resistance decreases and allows more gain. adding another resistor in series, while good in 90% of most circuits, will actually decrease your gain somewhat in a fuzzface.

yeah, its compromises. everything is. all a juggling act of balance.

anyways, the 2k pot will reduce the available gain to the stage, but drive the second stage a smidge harder.

really, i've seen 'em go 5 or even 10k, and it can be ok if set up right... you may find the bigger the pot, the larger the cap you can get away with. from the stock 22u to 47u will pretty much work... i like 33u for my personal ones, and tend to go 3.3u for input cap and 33n for output cap.

bypassing the 1k resistor with a small cap may help the treble response some. try 1n-3.3n in parallel with it.

if you want more balls, move the output cap junction from the 1k/18k junction to the 18k/c 2 collector junction.  this is one of my trade secrets. if ya make it footswitchable, you get a nice gain boost for leads. this is the circuit i sell as the fuzzface +

the resistor values shown will work, but probably not so toneful as possible.

i'd go with a 50k trimmer for the first stage collector, and figure it being about 18k where the sweet spot will land with most q's. also, q2, is gonna want i bet more like around 5k than 18k, so try another 10k trimmer there.

that way, you can purposefully dial in each transistor for best dynamics and best tone with least noise.

you may find a really small capacitance between c and b of q2 will help with the treble when the effect is rolled back.

remember, a fuzz is really just a treble booster with too-big input caps for all intents. its supposed to get glassy and crystaline when rolled way back. turn your guitar tone knob down.

google up "wolf computer" for some great ideas, too.

messing with the biasing via the c resistances will get ya a long way. i never cared for the mayer mods. loud, fuzzy, yes, but not so toneful.

with a fuzzface, set the BIAS via c resistors... set the GAIN via e to ground resistors. real small resistances, i'm talking say, 10r-220r can make HUGE diffs in how the face will react too.

by messing with the e resistors, you can effectively limit a transistor to a useful gain range. the low hFE ones i usually use are around 215 hfe consistantly <si, not ge... i rarely use ge anymore in these things after learning more about them> so a 47r on q1 and a 100r on q2 gets the gain about in the ballpark, and then use the c resistances to bias them.

you may find slightly higher bias point, particularly on q2, will darken up the fuzz a little bit, and make it more tubey and organic. most folks reccomend biasing to half voltage,  i tend to like it more like around 6 volts. more volume, more dynamic, not as bright.

i'd reccomend the initial biasing be done with the guitar on about 4, so ya get the "cleanest" guitar sound with the guitar rolled back.. ideally, ya want it to sound bypassed but with a little more compression when the guitar is rolled back.
messing with the trim pots you can really get on top of it.

the 1k makes it louder, but also brighter cuzza the gain bump. you can exploit this too. a smaller resistor will be a little darker. if ya go below 220r, expect problems with too much current smoking your pots.. go with at least a 1/4 watt resistor.

i tend to like 560 or 680r there.

the output pot matters, too... max brightness is 500k. but 250k, 100k both work well as well.

this is all fairly subjective and based on my personal experience with this circuit, and probably runs counter to any actual EE knowledge... but EE's are trained to minimize distortion.

my monkey fingers are trained to maximize and refine distortion. so... take my advice as what it is, if ya feel experimental.

the breadboard is your friend.

[fuzz guy]

Thanks for all the great replies. I'll try a C1k for the Fuzz control and see where that gets me.

As far as all the other stuff, I'll most likely get a breadboard at some point and start messing around with ideas. So far I've only built a couple pedals from kits, but I can already tell I'm going to want to experiment and tweak some of these circuits.

Thanks again for sharing your knowledge, it is much appreciated.