building a fuzz face... what should the third knob be?

[gutsofgold]

I have an old enclosure here that is already drilled for three pots. A buddy wants a fuzz face built into to it but I don't know what to do with the third knob.

I'm thinking...

external bias control
input cap blend (like on the ez face)
pre-gain/smooth control (variable resistor at the input)

Which would be the most useful/practical to you? I haven't tried any of these to be honest, but I don't think the bias control would be practical since it's a silicon fuzz and he wants it as smooth as possible. The blend cap knob seems cool but doesn't the 2.2uF already let in the entire signal? And has anyone used a pre-gain control on a fuzz face? Does it really smooth things out?

[Focalized]

Pre-gain is good. Cleans up the bass. Gives you less fuzz. The guitar volume does that of course but there's more to mix around with.

I actually like to fix the gain at max and add the bias and the pre-gain for my three knobs.

[darron]

don't know if it would work well, but you could make a sag knob too. just a thought.

[reveriesof]

blendable output cap is more interesting to me on the fuzz face.  depending on the setup i find a simple tone control (like mark hammer's stupidly wonderful one) can help tone down the harshness if your friend likes the extreme fuzz settings; good to have this switchable as it can make it hard to top unity gain

[burdt]

you can put a pot in there and don't connect it to anything. then insist to your friend that you hear an obvious difference as you turn it...

all kidding aside, a sag pot would be sweet. find a usable range, it doesn't have to be extreme.

[Mugshot]

a sag knob definitely. on the boutique Si FF project on GGG, i think the mid knob is some sort of a sag pot that runs in parallels to a fixed resistor. controlling the mid knob decreases the 1K before hitting the circuit. makes the circuit more gritty.

[liquids]

The pre-gain option is good option for most fuzz faces.

I've ironically got the same situation right now - a GGG enclosure I've never used and decided to make into a fuzz face.  I made the third knob a tone control. What I've liked the most in almost everything I'm working on is sending the effect volume pot out into a well biased buffer stage.  Then, out of the buffer and cap, I run a rat-type tone control (series resistance) via a small value pot (5k, 10k, 25k) which is my 'third knob.'  In front of the pot I put a small resistor (1K or less) and a cap to ground.  This simple page has helped me a lot in that regard: http://www.muzique.com/schem/filter.htm 

This way, with the pot wide open there is virtually no audible resistance/high end loss, for all practical purposes it is as if there was no tone control there at all, which is good option for a fuzz face.  If you dial in some resistance you can get some high end smoothness.  Makes a fuzz face far more versatile if you ask me.   You could also sub a SWTC I believe.

Ideally you'd want to test what values you like on the breadboard  ...but if you are averse, you can just go with 10k pot and socket the cap: 10k and .0047uF/4.7n is usually a nice starting point.

[fuzzo]

Good topic I have the same idea. A third control to improve the possibilities of sound.

Liquids, t he fuzz stays the same with the tone control or you loose something in the fuzz sound ?

[liquids]

If you are not averse to buffers post-fuzz, than no, nothing is lost. If you pick your components carefully, this kind of tone control run wide open should yield no noticeable tonal change as if it were not there; thast that point--it's just a buffer stage with a R-C beyond audible, let alone guitar frequency range, with minimum resistance.   

Go to this site and plug in 470 and .01 and look at the corner frequency. Play around with values.  Note that "this calculator assumes a low source impedance," i.e. something easily obtained through a good buffer. 

[fuzzo]

Ok thanks , I keep that idea in a corner.

Any buffer type works or a jfet or AOP is better to follow the fuzz ? you placed the tone control after the volume pot ?

What do you think about adding a Midboost/midcut like the one used in superfuzz to that fuzzface circuit ? Someone has already tried that ?

[liquids]

Any buffer type works or a jfet or AOP is better to follow the fuzz ? you placed the tone control after the volume pot ?

Experiment.  I've preferred BJT buffers with a 'noiseless' biasing scheme, sit the base at least one diode drop above half the positive power supply.  You may prefer other buffers.  Choose what buffer you prefer, so long as it is clean and suits your taste.

I put the tone control before the buffer: 1) because the buffer can handle any loading of the volume pot 2) so that the buffer isn't being slammed by the hot signal the fuzz generates, which I think could make the buffer itself distort  3) a volume pot will potential add some loading, so there is no reason to put it after the volume pot, rather than before the volume pot, as the buffer is effectively reducing any loading, so that the tone and volume pot don't 'interact' so to speak.

[fuzzo]

Ok thanks for that explanation. I takes note and see i'll add that to my next fuzz face circuit.

Otherwise, any ideas about a third Fuzz face control ? (I see some schematic where there's a booster (with a gain knob) before the fuzz circuit ) 

[Hanglow]

A rangemaster can sound good into a fuzz. If you put a switchable pot in there you could use it to switch the rangemaster in and out and it as an effect only needs one control for volume.

[CynicalMan]

a sag knob definitely. on the boutique Si FF project on GGG, i think the mid knob is some sort of a sag pot that runs in parallels to a fixed resistor. controlling the mid knob decreases the 1K before hitting the circuit. makes the circuit more gritty.

It's a 1k linear pot wired like a variable resistor in parallel with a 1k resistor.
The schematic is here:
http://www.generalguitargadgets.com/pdf/ggg_ff5_sc_b70.pdf

There is an error in the schematic. R2 and R4 should not be connected.

[hoostavah]

Pre gain boost+1. Also a master volume? An idea ive been tossing around for a while. Having a post fuzz master volume would be coll so you could have max fuzz without it being as overbearing.

[darron]

Pre gain boost+1. Also a master volume? An idea ive been tossing around for a while. Having a post fuzz master volume would be coll so you could have max fuzz without it being as overbearing.

I'm not sure I follow? Isn't the level control after the fuzz stage a master volume control?

[wavley]

I built kind of a GGG 60's fuzz face with some changes to a few values to taste, NPN, and the Jack Orman pickup simulator.  I find the contour and bias to be both quite usable.  Though if I had to choose I guess it would be the bias

[WGTP]

Bias - if you friend wants to dial in a "sick" sounding fuzz - Would this be similiar to "sag"?

Cap Blend - rolls off the bass at the input - you can also do this with the by-pass cap on the "fuzz" control

Input pre-gain - increases the input impedance, making it brighter, while reducing the input

Tone control - rolls off the highs, after the distortion

IIRC the 3 knob Tonebender has a tone control that rolls off the bass after the distortion - http://fuzzcentral.ssguitar.com/3knob.php

You need more holes...   

[WGTP]

What about a BMP tone control?   

[edvard]

Burst.