´Zoid Face a.k.a. Schizoid
An enhancement of a pinkjimiphoton designed versatile silicon fuzz face
last update: Feb 6, 2020
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I was traversing the web and stumbled over Brother Photon´s works. I was intrigued by the schizoid face, which is a fuzz face with two modes (a polished one and an evil one) and got in contact, since recently they blur the images on D.I.Y. forae.
After building some GE devices that come wrapped with some inevitable hiss, I set out to build this one.
From past experience I know fuzzes are sensitive to driving impedance as shown in one of my earlier articles, it makes the guitar´s volume knob behave differently and makes the FF sound different. Not enough with that, the guitar signal is loaded down and loses clarity progressively. A buffer, which is normally called for rescue, is said to make the FF sound hard, but without, some other pedals will simply not interface with a stock FF.
It is not true that the FF interacts with the volume control on the guitar, in a way that, say, a high capacity cable may form a resonance circuit together with the pickup when the volume is fully up.
So I like to buffer my faces. Fortunately, this is straight engineering applied. Even more fortunate, it is easy.
It turns out that this FF unit, GE or not, sounds and behaves much like old GE units you can hear on the internet.
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Transistor choice: from my axis face silicon project I had some PN2369A transistors left over (hfe=60), that appeared to work best in pos1. For pos.2 a 2N2222 was lying around (hfe=190) which turned out to work great. Some other, lower gain type, appeared more trebly and less smooth. This is really a matter of trying, but as explained on Fuzzcentral and in R.G. Keen´s Technology of the Fuzz Face, the magic lies in the gain factors. Even a medium power transistor like BD139/140 does work, those have lower gain.
I used a b-c cap of 22pF (Styroflex), 47pF appeared to big. The bias pot appears to settle at 3.5kOhm for greatest clarity.
Bias Emitter Resistors: I fiddled around with these, and ended pretty much with slightly different values for the hfe values chosen. This resulted in a value of 120 Ohms for the first stage and 82 Ohms for the second stage. For the collector, PJP recommends the following biasing procedure:
Input Capacitors: I found that in both modes, even with single coils, the input caps are fairly big, i.e. the low end content too big, which does lead to the typical FF mushy low end. While this may well be wanted in some situations, I found myself permanently twiddling the bass cut on the guitar when switching between the modes.
It might thus be a good idea to make the big capacitor (Photon Fuzz side, what I call the evil and bodacious Mr. Hide side) slightly smaller (I used 2.2 µF) and the Stupid Fuzz side (what I call the anally retentive Dr. Jekyll side) smaller by, say, half.
I originally had a 3.3 µF electrolytic capacitor in the first position, but it turned out that due to the buffer in front (and a signal with a DC offset on it) the right polarity could not be guaranteed, so I replaced this with a non polarized cap.
Levels: when switching between the faces, some output level difference is noticeable. This may be useful or be remedied in the future, time will tell.
Pots: PJP suggests a type A pot for the Fuzz control (log), however most commercial units use a type C (antilog). I installed this and it spreads the usable adjustment range nicely apart. The output pot is type A.
LED annunciation: it appears that upon switching a fairly loud pop is audible, which disappears if the LEDs are removed. This is a clear sign for LED inrush current creating a current surge that is picked up by the circuit. This is a common problem and is exaggerated by the fact that several LEDs are switched at the same time.
I soldered 2µ2 capacitors (non polarized) across the control lines between red and blue resp. red and green. This efficiently slows down the current peaks to make switching pops bearable.
TB MK-II switch: (later addon)
By chance I found out that bridging the buffer´s drive resistance, catapults us into Tonebender Mk-II territory. This differs from a FF by an amplification stage preceding it. Looking at the schematic, this has a drive impedance of 10k, albeit with some gain. Since the buffer´s series resistance forms a voltage devider with the FF´s input impedance (approx. 2k), bridging this yields a gain up step of about 6. Definitely into Mk-II territory. Great sound as demonstrated in the sound section. This eminently justifies the addition of an unobtrusive little switch on the side.
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Due to the lack of a genuine GE FF I compared two devices with the ´Zoid face
All three FFs can´t deny
their common heritage and are obviously in the same
ballpark, with the Axis Face Silicon being a bit
colored. The ´Zoid Face however is very flexible and
sounds totally uncolored. An extension of the guitar.
I´ll demonstrate that in the sound samples. It cleans
up reasonably well, maybe faster than the GE type and
has very many nuances of timbre you can adjust with
the guitar volume.
The Brontoboost is different
since it is built on a different basis. So GE alone is
not all. It is the FF dirty goodness.
First, if you are using any
FF type circuit, a bass cut facility on the
guitar is strongly recommended. This is not stock on
most guitars, but very helpful for overdriven sounds.
It helps to dramatically clean up distorted tones. Low
end gets in the way of the bass guitar anyway.
Secondly, never run a FF
into a clean amp. It will sound brittle and
awful. Try it. Either you push your amp over the
proverbial onset of clipping through sheer
volume, or put a mild, tone-shaping overdrive of
your choice after the FF, which emulates exactly this.
The overdrive, as insignificant as this may be,
does somthing beneficial to tone. For the following
sound samples I use exactly that.
So bear in mind, any recording
you hear on the web, always reflects the whole sound
chain, which is where of course those guys are
cheating you. There is nothing constant and thus
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The recordings have been done using the following setup and no further processing:
A feq quick and nasty takes. No exercise in timing or else. Crank you speakers.
A few tests regarding buffered / unbuffered and an alleged similarity with Tonebenders MK2:(...)
SHAME. I fell for the age old trap.
I turned the Fuzz control down and lo and behold... apart from a little difference in loudness, both variants sound largely the same! Explanation: the 10k resistor with the 2k input impedance forms a voltage divider, kind of an input attenuator. The FF stage gets hit way harder. Another theory up the swanee.
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 Pink Jimi Photon, Schizoid Face, youtube
 Pink Jimi Photon, Schizoid Face, freestompboxes.org
 Pink Jimi Photon, Schizoid Face, diystompboxes.com
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