Fuzz Face tone control. Nobody thought of this?

[Morocotopo]

Hi gang. I´ve been struggling with the Fuzz Face, eventually I tried the Fuzzcentral Axis Face, a silicon, negative ground variation. Works rather well, but I never liked the Face´s high end, too fizzy. That schem uses a 0,033 uF cap across the original 330R (1K2 in this schem) to tame high end. But still too fizzy. When going to sleep, a lightbulb went off, and I came up with this tone control (before this I tried LP filters at the output, but they didn´t satisfy me):



Works quite well, tames the high end, gives, at least to me, much more versatility to this classic schem.

Now, I can´t believe I´m smart enough to be the first one to do this... anyone ever tried this idea? I, at least, never saw it anywhere...

Also, anyone sees any disadvantage to this mod? I mean, it works, but I don´t know if it causes any sort of trouble, I´m just a hack with a breadboard!

[Joe Hart]

It should be fine because the net result is still the circuit seeing a cap of some value. Neat!!
-Joe Hart

[Chugs]

Weirdly enough, I thought of the same idea the other day after adding an input blend to a fuzz circuit. Great minds think alike!  I haven't tried yet though. How much tonal variation does the blend give?

[Gus]

FWIW

This was first with the Low Pass and the 100 ohm emitter/10K collector.

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

http://www.diystompboxes.com/pedals/3tran.JPG

http://www.diystompboxes.com/pedals/gusJH2mod.gif

http://www.diystompboxes.com/pedals/rocket.JPG

http://www.prodigy-pro.com/diy/index.php?topic=32333.0
some sound samples

[Morocotopo]

Nice schems Gus, I haven´t seen your work before. Would you care to explain the function of the 100 Ohm resistor in the emitter of Q1? I´ve never seen that before. Don´t be mad, sharing is like that... 

Chugs, it has a nice range of high end taming. At one extreme it´s the usual mosquito cloud, at the other it gets quite creamy.

[John Lyons]

Ariel
That is the first time I've seen that configuration used in that place of the FF.
I've used a cap across the collector resistor and even the input and output blend
caps but I had not thought of the cap across the collector as a blendable cap.
Nice one!

[joegagan]

nice thinking.

interesting how beautiful solutions and ideas come to us when we are half asleep, waking up, dreaming.

[Morocotopo]

Yep Joe, half asleep is good.



Not ALL the time, mind you. But, maybe that´s the key to Keith Richard´s success?

[Quackzed]

yeah , that looks like a keeper. but i'm not sure how much more abuse my fuzz can take  one more mod.

[Paul Marossy]

interesting how beautiful solutions and ideas come to us when we are half asleep, waking up, dreaming.

That's happened to me many times. But it's not always DIY related stuff.

Clever idea for the tone control. 

[brett]

Hi
the variable roll-off is a super cool idea.

my 2c worth on the 10k/100ohm method...
The small emitter resistor (e.g. 100 ohm) seems to be a good idea, and means that you could use a garden-variety Si transistor as Q1 instead of a Ge without getting massive gain.  But consider what this does to the biasing, input resistance and tone.  If, for the purposes of comparing bias, we imagine an NPN, negative ground fuzzface, the base of Q1 is at 0.3 V (because it is one p-n junction above ground).  Si fuzzfaces have the base at 0.7 V.  Therefore, a Ge fuzzface has a lot less headroom and there is more clipping and the clipping is more asymmetrical than for an Si transistor with a similar hFE (e.g. a 2N2369A).  Also, the input resistance is low (proportional to the hFE and about 15k-20kohms), giving creamy tone and significant sag and bloom.

Now, add an emitter resistor.  The bias rises by the Ie x Re (about 0.05 V in the case or 10k/100ohms) and the asymmetry in the clipping falls a bit.  The input resistance is close to the hFE x the Re (typically 40k).  This means there's a lot less sag and bloom (hardly any compared with a low hFE transistor).  These may be reasons why Ge appeals to so many people, even though their availability and quality are low and the price and nuisance value is high.
cheers

[mac]

Bien pensado Ariel!

You gave me another idea I'll try tomorrow: I'm going to replace the 330R with a 500R or 1k pot, wiper -> cap -> Vcc.

mac

[Morocotopo]

Gracias Marcelo! Muy de vez en cuando la neurona se activa...



You mean, R and cap in series? What would that do? Hmmm.

[WGTP]

Seems like someone did the variable cap deal with the big electrolytic on the Fuzz control some time back...   May have been Joe.  The input cap also.  

Seems to be enough places on the FF to add 1st order low pass filters that they end up cascaded for 2nd 12db/oct or 3rd 18db/oct order roll off. 

[mac]

You mean, R and cap in series? What would that do? Hmmm

No, the cap is in parallel with part of the pot. I tried it today and it works fine.

          500R linear
vcc ------//////----------//////------Q2 collector
             |              8k2
            === 47nf
             |
vcc ---------


mac

[Morocotopo]

Oh, ok. Functionally it´s the same as my mod? Or different? how does it sound?
I´ll see if I can make some sound clips of mine.

EDIT: Ok, some quick, out of tune, semi awful sound clips. One straigt into the computer via mixer:

http://www.zshare.net/audio/75460839a2acfda4/
Fuzz Face tone test no amp sim.mp3 - 2.56MB

First with tone 100%, then half, then 0%. Some guitar vol control fiddling. P 90´s mid position.

Same through a software amp sim, clean amp setting:

http://www.zshare.net/audio/75460927958e8946/
Fuzz Face tone test w amp sim.mp3 - 2.56MB

[Electron Tornado]

Yep, I'm diggin' it. Sounds nice.   

Going to have to try it.

[mac]

It works different because when cap is on the vcc side it does not cut highs.

mac

[Morocotopo]

So it goes from "not cutting highs at all" to a variable amount of cut? Is that right? In essence, a tone control with more range?

[mac]

So it goes from "not cutting highs at all" to a variable amount of cut? Is that right? In essence, a tone control with more range?

Yeap. I used a 47nf but can be increased to 100nf to cut even more highs.
Here is the schem (have you ever tried to draw schems using Paint?  )



mac