Comparing Circuits: Fuzz Face vs. The Fuzz Factory

[YouAre]

Hello all!

I would like to open up an analysis of the Fuzz Factory, using the familiar Fuzz Face for context, to help demystify the circuit for the unfamiliar...and to check that my own understanding is correct 

Firstly, I'd like to post the links to the schematics to facilitate part number references:
Fuzz Factory: http://www.madbeanpedals.com/projects/Zombii/docs/Zombii_ver.5.pdf
Fuzz Face: https://www.electrosmash.com/fuzz-face

I've seen rumors on site that aren't dedicated to circuit design/analysis that the Fuzz Factory is a "suped up" fuzz face, but usually pay no heed to those conjecture. I did a search for comparisons on this site, but I didn't find anything. My apologies if I missed something!




But look at the GE PNP Fuzz Face next to a Fuzz Factory, I'm actually seeing some weight to this!

It seems that the Fuzz Factory is...a GE PNP Fuzz Face with:
-Gate: Additional control over First GE Transistor (Q2 on Factory, Q1 on Face) Collector Resistance
-Comp: Control over non-bypass emitter resistance of output GE PNP (Q3 on Factory, Q2 on Face)
-An alternative method of achieving a volume control (Lets talk more about this!)
-"Stab" control, voltage sag.
-Applying positive to the emitters and grounding the collectors, as opposed to positive voltage to the collector and grounding the emitter in the Face (Let's talk more about this too!)




Admittedly. Transistor fuzzes are a little vexing to me, so I could definitely use your guys help!

The Fuzz Face has fixed collector resistances on the output transistor stage, which is coupled with a cap to the volume control. The Factory however modulates these resistances via a pot, which couples to a fixed output resistance. What's the advantage of this? Does this mess with the bias of the transistor at all (I wouldn't think so, cause it seems like we're "tapping" the collector resistance), or is this another way of achieving an output volume circuit?



I love that we have a PNP fuzz running off +9V by reversing where we apply our power supply and ground. Is there any reason we can't do the same to a stock fuzz face? What would be some of the challenges if we tried this power supply arrangement on a fuzz face circuit?



The factory's input NPN Booster. Does this offset the characteristic low input impedance of a GE Fuzz Face on toping of boosting the input to create a different beast? Or is it just boosting the ever living hell out of the Fuzz Face Portion.



Is there anything else interesting that someone else picked up on that I missed?

Thanks all!

[PRR]

> input NPN Booster. Does this...

Not sure what you are asking here. The Q1 stage is easy to rough-analyze. If you are unclear on that, you maybe want more electronics background than can practically be taught in a forum of dilettantes.

> another way of achieving an output volume circuit?

Look at the whole output network. It must pass DC. We want a large signal cut, and adjustment from there down. We need a DC block, and a cap bleed. Counting pot as 2 parts, that's at least 5 parts.

There are 13 ways to connect 5 parts.

Several of these do not do the job we need done; that still leaves several different ways to do it.

[YouAre]

Thanks for your reply!

> input NPN Booster. Does this...

Not sure what you are asking here. The Q1 stage is easy to rough-analyze. If you are unclear on that, you maybe want more electronics background than can practically be taught in a forum of dilettantes.

From what I know of the Fuzz Face, one of the desired characteristics of the fuzz face is it's interaction with the guitar's volume pot. The downfall is that any buffered signals in front of it eliminate that favorable trait. Pedals like the Earthquaker Devices Erupter include a transformer ala AMZ's guitar pickup simulator.

I was opening up discussion to your musings on what an NPN common emitter booster does to that characteristic low input impedance of the circuit.

> another way of achieving an output volume circuit?

Look at the whole output network. It must pass DC. We want a large signal cut, and adjustment from there down. We need a DC block, and a cap bleed. Counting pot as 2 parts, that's at least 5 parts.

There are 13 ways to connect 5 parts.

Several of these do not do the job we need done; that still leaves several different ways to do it.

Understood. I was commenting on the difference between having the volume pot before the cap vs. after. I typically see it after, and am assuming this was done on purpose. Unlikely to get an answer straight from the horse's mouth, I'd like to open it up to your experience as to what the electrical difference is.

Thanks again!

[POTL]

It's not really Fuzz Face, it's rather a slightly simplified version of Tone Bender MKII 

[MaxPower]

A circuit simulator like LT Spice or Tina-ti is handy for experimentation and trying to figure out what's going on.

[YouAre]

It's not really Fuzz Face, it's rather a slightly simplified version of Tone Bender MKII 

Simplified? I see more parts! But that's for pointing that my way! Completely forgot about that one, and see the similarities as well!

I'm REALLY interested in the voltage arrangement, in how he's applying positive 9V to get the circuit to work. What prevents us from doing something similar to a regular fuzz face or tonebender to avoid using a charge pump?

A circuit simulator like LT Spice or Tina-ti is handy for experimentation and trying to figure out what's going on.

I am an absolutely avid LT Spice user, and will simulate every circuit I want to understand on it. However, I know to use it for the expected behavior of a circuit. With fuzz circuits, I'm also interested in the possible. Knowing everyone and their brother has built a fuzz face (except me), I'd love to know everyone's experience with their experimentations.

[MaxPower]

Who's using positive 9 volts?

Have you tried the axis face? A good fuzz face variant. There's a website called fuzzface central I believe (or fuzz central?). It might be of some use.

[brianq]

Have u read R.G. Keens "technology of the Fuzz Face"? U may find some of your answers there? I believe Steve Daniels at smallbear also has an article on his site, I think it's called fuzz face FAQ?

[YouAre]

Who's using positive 9 volts?

Have you tried the axis face? A good fuzz face variant. There's a website called fuzzface central I believe (or fuzz central?). It might be of some use.

The Fuzz Factory is! Check the link in my original post, it's actually a pretty nifty arrangement!

And yeah! I peeped the axis site after someone recommended I check out the Tonebender MKii. They made some interesting changes to the silicon variant to smooth it out.

Have u read R.G. Keens "technology of the Fuzz Face"? U may find some of your answers there? I believe Steve Daniels at smallbear also has an article on his site, I think it's called fuzz face FAQ?

Oh man, forgot about the RG Keen article, thank you for reminding me!

Scoped it real quick, and it gives a more easily simplified breakdown of the gain stages than electrosmash, a great reference! It does stick to the traditional voltage arrangement.

As far as I've seen thus far, The Fuzz Factory is the only pedal I've come across that has that voltage arrangement. Positive 9V applied to the emitter and collectors grounded.

[POTL]

It's not really Fuzz Face, it's rather a slightly simplified version of Tone Bender MKII 

Simplified? I see more parts! But that's for pointing that my way! Completely forgot about that one, and see the similarities as well!

I'm REALLY interested in the voltage arrangement, in how he's applying positive 9V to get the circuit to work. What prevents us from doing something similar to a regular fuzz face or tonebender to avoid using a charge pump?

The first stage of amplification looks much simpler than in mkII
The remaining changes are the replacement of the fixed resistors by the variables and the addition of the potentiometer gate parallel to the potentiometer drive.
In the charging pump, I see no problems.
I tried to turn the power, but the circuit worked incorrectly, the pump is inexpensive, it takes not much space, but relieves the headache)

[brianq]

DBA puts V+ on emitters & grounds collectors on quite a few of their circuits? Nothing new

[YouAre]

The first stage of amplification looks much simpler than in mkII
The remaining changes are the replacement of the fixed resistors by the variables and the addition of the potentiometer gate parallel to the potentiometer drive.
In the charging pump, I see no problems.
I tried to turn the power, but the circuit worked incorrectly, the pump is inexpensive, it takes not much space, but relieves the headache)

You tried to turn the power with which circuit? Sorry, lost me there.

DBA puts V+ on emitters & grounds collectors on quite a few of their circuits? Nothing new

Ah! Which circuit do you remember does that? I'd love to take a look at that too. Thanks!

[brianq]

They have quite a few, supersonic fuzzgun & soundwave breakdown, later fuzz war are only names I can remember? But there's more, they love making noisy oscillating circuits

[POTL]

The first stage of amplification looks much simpler than in mkII
The remaining changes are the replacement of the fixed resistors by the variables and the addition of the potentiometer gate parallel to the potentiometer drive.
In the charging pump, I see no problems.
I tried to turn the power, but the circuit worked incorrectly, the pump is inexpensive, it takes not much space, but relieves the headache)

You tried to turn the power with which circuit? Sorry, lost me there.

I tried to get to work properly germanium fuzz pnp from the classic + 9V, but I will say so, almost always had to change something in the scheme.
I did not want to work with voltage converters, but for the past almost 2 years and a huge number of collected different distortion effects, I made the following conclusions for myself:
1) "try, experiment, if it does not turn out not to be disappointed"
2) "You can try to deceive the system many times (especially when the technical knowledge is small), but in time you will understand why everyone does as they do, and not how you want"

[brianq]

Ever tried the Vorpal fuzz? all easily found off the shelf silicon transistors in that version.

[mac]

I bet someone at Zvex was breadboarding a Fuzz Face, pots everywhere to fine tune the thing as we usually do, and had the brillliant idea to translate what was on the breadboard into a commercial unit, with oscillations and all

There are 13 ways to connect 5 parts.

I never knew why I had to study Graphs Theory, until now

mac

[PRR]

> I never knew why I had to study Graphs Theory

Yes, that picture struck me. If for "matchstick" you read "2-leg electric part", it works. Sometimes we have a herd of parts not doing what we want, another arrangement might be better. Or we wonder why brand B does this and brand D does that. Knowing there is a large but finite total number of ways to do it may focus your study.