Fuzz Face guitar effects pedal

After putting our Fuzz Factory guitar pedal on hold - while we wait to get hold of some AC128 germanium PNP transistors - we were keen to make something - anything - that could make a noise.

It's often said that the Fuzz Factory is a Fuzz Face with knobs on. Quite literally.
So while we don't have the PNP transistors we need to complete our Fuzz Factory pedal, we do have some metal can BC109 transistors.

And these transistors are used in an alternative NPN, silicon-transistor based design. Here's a schematic based on one of the many designs available online:

Fuzz Face schematic by chris_holden2495

It's a basic twin-NPN design, and uses only a few discrete components (resistors and capacitors mainly, and a couple of potentiometers) so it didn't take long to throw together a PCB for it:

Fuzz Face PCB layout by chris_holden2495

This layout is press-n-peel ready - simply print and transfer onto copper board.
Here's the silkscreen layout, to position the components in the right places (from a top-down view, with the copper traces on the underside of the board)

The PCB has been designed to be not more than 24mm deep, allowing it to fit inside a stompbox enclosure at 90 degrees to the "face" of the box - meaning the potentiometers can be mounted directly onto the PCB (no nasty wires running about the place) but the orientation of the PCB means there's still plenty of room inside for plugs, sockets, pushbuttons and the all important battery.

(this photo showing PCB orientation is actually of the Fuzz Factory, not the simplified Fuzz Face, but demonstrates the principle of fitting a narrow PCB into the box at right-angles)

So while we've got a working effects pedal (see video below) it's going to have to wait a day or two before it can go into it's final housing. It turns out that being a ham-fisted oaf in the workshop can sometimes be a bit of a hindrance. Apparently a hole punch is for marking where to drill a hole in the metal box - not something you should actually punch a hole with! I'll have to lighten my touch on the next box....

Here's a video demonstrating the effect pedal in use:

(I couldn't decide whether to have the fuzz on green-for-go, or have the light green and go red when the fuzz was activated. In the end, I went with green=safe, red=danger - so the LED goes red when the fuzz is active. Look out!)

All in all, quite pleasing for an evening's work. Sorry the write-up's not much; pretty much because I just banged this one out, so I'd at least have one pedal I managed to make (and prove works) myself!

Dallas Fuzz Factory guitar pedal with AC128 germanium transistors

I've recently been learning how to play my guitar.
Not just banging out chords, as I've been doing for over twenty years now, but actually play the thing. With riffs and licks and the like. I got the Griff Hamlin Blues Guitar Unleashed course, and his Five More Easy Blues Solos lessons, and set about learning some guitar leads.

I've had the courses for about 8 months now, and still haven't got round to really spending any time with them -  I'm not much further on than I was when I first tenatively plucked out the opening notes of Ugly Kid Joe's "Everything About You" back in the early 90s.

Someone suggested going to a live jam session - not only to learn from others, but to put myself in a position where I have to learn something new or interesting, so I've something to "show off" on the night. So I attended a couple of Blues Jam Meetups and have played live with a band a couple of times now. At one point I even got in front of the mic and sang a little song

One thing I'm not mad about is bands where the guitarists "compete" over the course of the night, getting louder and louder. But there I was, on stage, with 12 bars to fill with some guitar noise. So I broke out my three guitar licks I knew and played them. And it sounded ok. But what I really needed was an extra little bit of oomph, just for the guitar solo - after that night, I decided that what I needed was a stompbox!

About a million years ago - ok, about two-and-a-half - at BuildBrighton we ran a build-your-own guitar stompbox effect workshop.

It was really well attended and everyone - eventually (some returning the following week) - went away with a working pedal. So we have a design which we know works. But one thing that's always been a bit of a bugbear is how it was constructed using perfboard.

Sure, that's great for the workshop, as it demonstrated the "hack-it-together-yourself" approach we wanted to get across, rather than just a "solder-this-existing-kit-we-made" type of workshop. But it always felt a little bit incomplete. But, just for this project, a PCB just felt right. So we set about designing one...

The schematic is a slightly modified version of the original one, with all of the controls brought out onto the front of the pedal

Fuzz Factory Schematic

This design includes pots for

• stability
• compression
• gate
• drive and
• volume

The PCB layout was designed so that the pots could be fixed straight to it, and that it would lie at 90 degrees to the "face" of the box, to reduce the amount of space that the actual circuit board took up, inside the box.

Amazingly, after soldering everything (ok, most things) up, it all still fit in the enclosure just right

Here's the final pedal, with all the plugs added, pushbutton fitted and all controls in place.

Maybe we could ask Steve to design us a funky new sticker for the top surface.

The only slight problem we have with this now is that is uses some old-school AC128 germanium PNP transistors - and we haven't got any here to actually test the pedal with! Perhaps Jason will turn up with a pocketful of them at tonight's BuildBrighton Open Evening?

Buildbrighton stompbox grinding

Here's Joel from the earlier BuildBrighton Stompbox workshop getting busy with a new enclosure for a variation on the Fuzz Factory pedal we made. The box is actually an old (and he tells us, quite crappy) effect pedal, but with space for four knobs and a nice big stomping area, it's the perfect box to put his modified fuzz factory in.

The first job, of course, is to clean up the artwork and design a custom decal sticker. Joel attacks his enclosure with a wire brush mounted on an angle grinder....



Showing us how to do it properly - note the dust mask and safety goggles

BuildBrighton Guitar Stompbox Workshop

It's been a long, exhausting, but ultimately satisfying day, after running the BuildBrighton guitar stompbox workshop today. There was a sell-out crowd (plus a couple of last-minute attendees, squeezed in on the day) and we had a fantastic success rate - of 12 boxes, 10 were (eventually) working by the end of the workshop!

The boxes were based on the Dallas Fuzz Factory schematic, with a couple of tweaks. Firstly, as only two pots were to be exposed on the box (drive and volume) the others used were trimmer pots (compression and gate) so each person could create their own unique sound and capture it inside the box!

Fuzz Factory Schematic

As well as making the circuits on stripboard, everyone had a go at drilling their alloy enclosures in the BuildBrighton "dirty workshop" as well as fitting all the hardware and wiring everything up.

As well as creating a circuit board from the schematics using stripboard (veroboard), everyone had to wire up all the pots, footswitch and sockets and it was amazing to get ten fully-working pedals after about six hours hard work!

Jamie Matthews was the first successful candidate to rock out with his fuzz pedal

Note how you hear the tone/flavour of the pedal changing as Tom tweaks the compression and gate trimmer pots. These pots allowed us to tailor each pedal without having to swap out lots of different components

It didn't take long for others to follow:

Though not everyone was successful on their first attempt. Jon (in this video) actually managed not only to make a crackly pedal, but a direct short across the drive pot terminals in this pedal actually caused it to smoke (shortly after this video ended). When a tiny flame appeared, it was decided to replace his pot and capacitor, just to be sure!

Not so much smoke on the water as "smoke in the pedal"

But it was great to see genuine smiles break out - the real ones that you just can't hide - as more and more pedals fuzzed and buzzed into life

For that authentic rock sound, we were using 2 x germanium transistors in each pedal. Germanium transistors are not as stable nor consistent as silicone ones, so some have a higher gain than others. Real pedal enthusiasts have been known to sit and try out loads of different transistor combinations, to get that "just right" tone. We included sockets for our transistors to all people to do this if they wanted. As time was tight, Jason spent a few hours testing all our germanium transistors and sorting them into (relatively) high and low gain. We used a low gain for Q1 (see schematic) and a high gain for Q2.

Joel, from GAK specifically asked for two high gain transistors to make  really "hot" pedal. You can hear his pedal going crazy when pushed to the top end of the range 

Here's the documentation that everyone was following. Use it to create your own fuzz-factory clone!

Stompbox Workshop

Multi-effect pedal update

The Ferric Chloride yesterday evening, so we got on with etching our multi-effect pedal board, made with the (much cheaper) press-n-peel alternative. The result was pretty impressive. In short, the cheaper alternative works as well as the real thing for us. Which is just as well, as we've invested in about 50 sheets of the stuff!

A bit of drilling and filling and a bit later, we had a populated board!

Of course, the eagle-eyed will spot that there are still components missing off this board. Can you believe we can't find a 10K or 1K rated resistor in amongst all the junk in the nerd cupboard?! It's not like we're after some obscure rated component, just some common-or-garden, everyone-uses-them 10K resistors....

Here's the board soldered up (minus a few critical components) complete with "pass-through" switches. By setting these switches, you can have the input signal directed straight to the output jack (clean sound), have it pass through the fuzz circuit then straight to output, have the input go to the wah circuit only, or have the input go into fuzz then wah before hitting the output jack.

Still not quite ready for testing, but it's looking quite promising so far....

Multi-effect pedal

We had a great time at BuildBrighton with our working fuzzface guitar pedal. New member Patrick even brought along a VOX wah pedal to get some Voodoo Chile type riffs going!

Which got us thinking about embedding our effect pedal inside a guitar, and how to simplify the circuit. So we came up with this idea - it's an effect pedal combining a fuzz face and a wah pedal. Either or both can be by-passed (so you can have clean, just fuzz, just wah, or fuzz going into wah).

In a future version, we're planning replacing the potentiometer on the wah (labelled VR3) with a digital pot. This will allow us to hook the wah effect up to a PIC micro-controller and use a 3-axis accelerometer to change the wah sound. Tip the headstock towards the ground to simulate rocking the pedal back, then move it upwards to rock the pedal forward.

The introduction of an accelerometer on the guitar opens up all kinds of possibilities (imagine hooking it up to the volume control: tip your guitar skyward, a la Slash, for a volume boost while solo-ing!) Any way, here's the first version of our multi-pedal:

Multi Pedal schematic

Multi Pedal PCB

Parts list:


C1 2.2uf  capacitor
C2 0.01uF capacitor
C3 22uF capacitor
C4 0.01uF capacitor
C5 0.22uF capacitor
C6 4.7uF capacitor
C7 0.01uF capacitor
C8 0.22uF capacitor
L1 500mH inductor
Q1 BC108 NPN transistor
Q2 BC108 NPN transistor
Q3 BC108 NPN transistor
Q4 BC108 NPN transistor
R1 33K resistor
R2 330 resistor
R3 8K2 resistor
R4 100K resistor
R5 68K resistor
R6 1.5K resistor
R7 470 resistor
R8 470K resistor
R9 22K resistor
R10 33K resistor
R11 82K resistor
R12 470K resistor
R13 10K resistor
R14 1K resistor
SW1 = DPDT switch
SW2 = DPDT switch
VR1 = 1KB potentiometer
VR2 = 1KB potentiometer
VR3 = 100K potentiometer

Working fuzz face pedal

Here's a video showing the fuzz face effect "pedal" working with a Peavy Raptor guitar and miniature Marshall amp.

There's a definite difference between "clean" and "distorted" sounds and we're keen to say that the whole thing works well. The only thing is, after trying out our board, Jason from BuildBrighton turned up and asked us to try out his design - and his works even better!

So we've ended up with two types of effects pedal. Our latest design is more of an "overdrive" distortion effect, whereas Jason's is very much more "fuzzy" - more reminiscent of the original FuzzFace.

(check out the video jump at about 0:44 where the video was paused while we swapped out "our" pedal for Jason's)

Fuzz Face with NPN transistors (MPSA18 amplifiers)

After amending our FuzzFace design to use a positive power supply, we've had a couple of enquiries about the schematic. Mainly that a few readers weren't familiar with the PNP transistors used (nor seeing them drawn "upside-down" in the circuit) so we've found a design that uses NPN transistors and different resistor values (including a potentiometer/variable resistor to adjust the amount of "fuzz")

FuzzFace with NPN transistors

Here's the PCB layout. We've not had chance to try this, as we're still waiting for some 20uF capacitors.

That said, we've a few 22uF caps lying around here (large black barrel electrolytic types) and since 22uF is just within the range of a 20uF with +/- 10% (and 20uF is within the range of a 22uF with +/- 20%) then it may just be a suitable replacement. We hope so, since 22uF caps can be easily found all over Farnell and eBay for just a few pence whereas the cheapest 20uF rated capacitors are about £3 each.

FuzzFace NPN pedal PBC layout
(print the above at 100% no scaling to create your own press-n-peel image for toner transfer)


Since simplifying the design (using 22uF instead of 20uF capacitor for example) we've managed to source all the components needed to make this pedal, so it's off to the nerd cupboard now to crack open the Ferric Chloride and get etching!