Bazz Fuss

A single-transistor fuzz, on a breadboard · By Onion Madder · Mess O' Pedals

Christian Holmberg's fuzz, and about the smallest real one there is: one transistor, one diode, one resistor, two capacitors. Rude, gated, and synthy on the note decay - notes don't fade so much as collapse, and that collapse is the sound people build this circuit for. Build time is about ten minutes, and this one you plug a guitar into.

The finished fuzz on a white breadboard on a dark bench, plugged in and playing. A small black transistor, a yellow film capacitor, a black electrolytic can and banded resistors sit along the left of the board, with blue, yellow and green flying leads running down to a potentiometer and two metal jack sockets lying in front. A yellow guitar cable is plugged into one jack and runs to a lilac practice amplifier at the right. A 9-volt battery feeds the black power module at the board's right-hand end, its green LED lit. — Built and plugged in. Ten parts, one transistor, and a guitar cable straight into a practice amp.

This is the third build in the breadboard series, after the Atari Punk Console and the Optical Theremin - and the first that's a proper pedal circuit, with an input jack and an output jack. Power is 9V DC - a 9V battery, or vape cells in series.

⚠ Before you start tap to expand / collapse

Two parts care which way round they go: the diode (the band goes toward the base - backwards and nothing works at all) and the two electrolytics (the stripe marks the minus leg). Get those right and there's nothing here that can hurt you or the parts.

Mind your power leads - 9V positive to the + rail, negative to the − rail, and nothing in this build should ever get warm.

If you power it from a salvaged lithium pack, the usual cell cautions apply - see Do You Want to Survive the Vapocalypse?

What you'll need

The parts list lives on the build sheet too - this version adds how to spot each part: the printed marking, the package, or the polarity clue.

1× 2N3904 or 2N5088 NPN transistor, TO-92 - spot it: the little half-cylinder with three legs and one flat face, part number printed on the flat
1× 1N914 or 1N4148 silicon diode - spot it: a tiny glass bead with a band at one end; the band marks the cathode, and where it points is the whole build
1× 100K resistor - spot it: bands brown-black-yellow, or meter it
1× 100nF film or ceramic - input cap. Spot it: printed 104. Either way round
1× 4.7 µF electrolytic - output cap. Spot it: a little can; the stripe marks the minus leg, longer leg is +
1× 100K pot - volume. Spot it: marked B100K
1× 100 µF electrolytic - supply smoothing. Same stripe rule
1× jumper wire - yes, just the one
Breadboard, 9V supply, two jacks - input and output
For the optional nastier version: 1× MPSA13 Darlington transistor and 1× 10K resistor (bands brown-black-orange)

Everything for the build laid out on a dark bench below the breadboard and its power module: a 9-volt battery, a small yellow film capacitor, two black TO-92 transistors, a black electrolytic can, a banded resistor, a glass diode, a potentiometer with blue, yellow and green wires already soldered to its lugs, and two metal jack sockets on white and black leads. — Everything you need, including the spare transistor for the nastier version at the end.

Reading the breadboard

Letters run along one edge of the board and numbers along the other. A hole is a letter plus a number - E10 is row E, column 10 - and the five holes in a bank that share a number are one electrical point: A10, B10, C10, D10 and E10 are the same node with five ways in. Turn the board so the numbers climb left to right; the whole build lives in the A to E bank and the pair of rails beside it - the F to J bank stays empty.

Check your power rails aren't split at the middle of the board. If they are, jumper across the break at both ends.

Quick reference - the whole build on one card

No 14-pin chip this time - the whole thing hangs off three transistor legs. Hold it right and the holes fall into place; this is the bench card.

╭───────────╮ │ 2N3904 │ flat face toward you, │ │ legs pointing down ╰──┤──┤──┤──╯ E B C E10 E11 E12

Emitter, base, collector - left to right, flat face toward you. Swap them and the fuzz stays silent. The diode's band goes toward the base (column 11).

The core

Emitter (E10) → − rail via A10
100K: collector (B12) → + rail
Diode: C12 → C11, band in C11

In

100nF: D4 → base (D11)
Input jack tip → A4
Input jack sleeve → − rail

Out

4.7µF: + leg D12 → D20
Row 20 → volume pot → output jack tip
Output jack sleeve → − rail

Power

100µF across the rails, + leg in +
9V: positive → + rail, negative → − rail

Steps 1–3 The semiconductors

Transistor first, then the jumper that ties its emitter down, then the diode. Get the three legs the right way round and the rest of this build is pushing parts into rows.

Transistor, jumper, diode
Step	Do
1	Hold the transistor with the flat face toward you and the legs pointing down. Left to right the legs are emitter, base, collector. Spread them and push them into E10, E11 and E12 in that order
2	Jumper: A10 to the − rail (emitter)
3	Diode: C12 to C11, with the banded end in C11. The band goes toward the base. Backwards and nothing works at all

There is no bias network here, which is the whole trick. The diode in step 3 does two jobs at once: it trickles just enough current into the base to switch the transistor on, and it clips the signal at the same time. That is why the orientation matters so much and why the circuit is so short.

The small black TO-92 transistor seated alone on the empty white breadboard, its three legs pushed into three adjacent rows and its flat face turned toward the camera. The power module and its red and black leads sit at the right-hand end. — The transistor in, flat face toward you. Every other hole on this build is measured from these three legs.

The same board with a short bare jumper added beside the transistor, linking one of its rows across to the neighbouring strip. The rest of the board is still empty. — The jumper that ties the emitter down.

A small glass diode added to the board, standing on bent legs beside the transistor with its dark band toward the transistor's middle leg. — The diode, band toward the base. Backwards it just goes quiet.

Steps 4–7 The passives

Resistor, then the film cap, then the two electrolytics. Same order every time, so you can see at a glance what is still missing from the board.

Resistor, capacitor, electrolytics
Step	Do
4	Resistor 100K: B12 to the + rail
5	Cap 100nF: D4 to D11. Either way round
6	Cap 4.7 µF, + leg in D12, other leg in D20
7	Cap 100 µF, + leg in the + rail, other leg in the − rail

A banded resistor now lies across the rows beside the transistor and the diode, its leads bent flat into the board. — The feedback resistor. That is the whole fuzz: one transistor, one diode, one resistor.

A small yellow film capacitor added upright on the board to the left of the transistor, its two legs in adjacent rows, with the rest of the circuit behind it. — The input capacitor. Everything before this point is your guitar, everything after is the fuzz.

A black electrolytic capacitor can added at the left of the board with its legs in the two supply rails, standing beside the yellow film capacitor and the transistor. — The supply cap across the rails. It is what stops the fuzz from motorboating when the battery sags.

Steps 8–13 Off the board: pot and jacks

Nothing else goes into the breadboard. The volume pot and both jacks live on flying leads, so this is the part you unplug when you want the board back.

Volume pot and jacks
Step	Do
8	Wire: A20 to either outer lug of the volume pot
9	Wire: the volume pot's other outer lug to the − rail
10	Wire: the volume pot's middle lug to the output jack tip
11	Wire: output jack sleeve to the − rail
12	Wire: input jack tip to A4
13	Wire: input jack sleeve to the − rail

The potentiometer now connected to the board by three flying leads in blue, yellow and green, lying on the bench just in front of the breadboard with its shaft pointing up. — The volume pot on flying leads. All three lugs are used, so it can reach silence.

Both metal jack sockets now wired in, lying on the bench in front of the board on white and black leads, with the potentiometer and its blue, yellow and green leads between them and the breadboard. — Both jacks wired. Input on the left, output on the right, the way everything here is wired.

Step 14 Power up

Power
Step	Do
14	Power: 9V positive to the + rail, negative to the − rail

⚠ If it doesn't work

Symptom → check
Symptom	Check
No sound at all	Step 3, the diode is backwards. This is the fault almost every time.
Still no sound with the diode right	Step 1 - the transistor legs are in the wrong order. Emitter, base, collector, left to right, flat face toward you.
Notes choke off and die early	That's the circuit, not a fault. Roll your guitar volume back if you want less of it.
Very dark and woolly	Step 5. Try 10nF (printed 103) instead for a thinner, spikier sound.
Thin and weak	Step 5 the other way - try 1 µF.
Hiss and squeal with nothing plugged in	Transistor gain too high for this build. Try a 2N3904 instead of a 2N5088.

Optional A nastier version

Swapping the transistor for a Darlington - two transistors in one package - raises the gain enormously. It needs a smaller collector resistor to stay usable.

The Darlington swap
Step	Do
15	Replace the transistor in step 1 with an MPSA13, same leg order, same three rows
16	Replace the 100K in step 4 with a 10K resistor, same two points

The 100K belongs to the plain transistor version and the 10K to the Darlington. Using the wrong one is why most Bazz Fuss builds on the internet are reported as too quiet or too wild.

How it works, in one breath

A transistor needs a trickle of current into its base before it does anything, and normally that takes a pair of biasing resistors. Here the diode does it - current dribbles from the collector through the diode into the base, parking the transistor barely switched on - and it clips the signal at the same time, two jobs with one part. Because the transistor is barely on, even a small guitar signal slams it into its limits both ways; and as a note decays the bias slides back toward off, so the sound gates out. That's the whole circuit, and why it's so short.

Things to try

Swap the diode. A germanium 1N34A is softer and quieter, an LED clips higher and louder and cleans up more, two silicon diodes in series gets closer to a proper fuzz.
Tame the gate. Add a resistor from A10 to the − rail instead of the jumper in step 2. Anything from 100 Ω to a few K drags it from fuzz back toward overdrive.
Starve it. Run it on less than 9V. Four or five volts is where it gets properly sick.
Turn it up. Put it in front of the mini amp and turn both up.

The Bazz Fuss is Christian Holmberg's circuit - shared free on his home-wrecker.com site and built by thousands since as a first pedal. This breadboard recipe, wiring, and words are my own. Build it, bend it, make it yours.