Bazz Fuss Build Guide

How to build the silicon Darlington Bazz Fuss on stripboard.
ImportantPrototype design

This circuit has been simulated but not built yet. The layout is checked against the schematic by the script that draws it, and the voltages in this guide are simulated, not measured. Consider trying it on a breadboard first.

Assembly Procedure

  1. Prepare your workspace

    Find a clean, well-lit area to work. You will need the following:

    • Soldering iron and flux-core solder
    • Small wire cutters and wire strippers
    • Multimeter (you use it to check cuts, parts, and voltages)
    • A 3 mm (1/8 in) drill bit or a stripboard track cutter
    • Heat gun or lighter for heat-shrink tubing
    • Helping hands, or similar device, to hold parts while soldering

  2. Gather the parts

    The Bazz Fuss is one gain stage. The original uses an MPSA13 Darlington transistor. This version builds the Darlington from two ordinary NPN transistors, QA and QB.

    CountPartValueNotes
    1Stripboard14 × 6 holes0.1 in pitch, strips along the 14-hole length
    2Transistors, QA and QBNPNA matching pair: 2N3904, 2N2222, BC337-25, C1815-GR, or S8050-D
    1Resistor, R110 kΩ (brown, black, orange)
    1Resistor, R21 MΩ (brown, black, green)
    1Capacitor, C110 µFElectrolytic. Any value from 1 µF up works; see below.
    1Film capacitor, C2100 nF (104)
    1Diode, D11N4148Or an LED; see below
    1Potentiometer, VOLUMEA100k16 mm, audio (log)
    13PDT footswitch9 solder lugs
    1LED and bezel5 mmEffect-on indicator
    1LED resistor4.7 kΩ (yellow, violet, red)
    21/4 in jacksStereo (input), mono (output)
    19 V battery snap
    —Hookup wire, link wire, heat-shrink tubing
    Your ChoiceUnderstanding Your Options - C1

    C1 couples your guitar into the transistor's base. The stage's input impedance is low, so C1 needs to be fairly large to pass bass. 10 µF keeps all the low end. Anything from 1 µF up works, including a 1 µF film capacitor, with a little less bass at the smaller values. If you use an electrolytic, its positive lead goes toward the base.

    Your ChoiceUnderstanding Your Options - D1

    D1 sets the bias and does the clipping. A 1N4148 gives a tighter, more compressed fuzz. An LED in the same position raises the collector voltage, which gives more output and a more open sound. Any color works, and each color sounds a little different. You can install D1 in a pair of sockets, or solder it in lightly, to try both.

  3. Try it on a breadboard (optional)

    Because this design hasn't been built yet, you can build it on a half-size breadboard first to hear it and try different D1 parts. The breadboard layout wires the jacks straight to the circuit, without the footswitch. Select the diagram to open the full-size image.

    Bazz Fuss breadboard layout: QA and QB, R1, R2, C1, C2, and D1 on a half-size breadboard, with the volume pot and jacks wired off the board

  4. Learn the board

    Stripboard has copper strips running along its length. Every hole in a strip is connected, so the strips do the wiring for you. You break a strip where two parts must not connect.

    Holes are named by row and column. Rows run A to F from top to bottom, and columns run 1 to 14 from left to right, with the parts on top and the copper underneath. For example, B12 is row B, column 12. Keep the layout diagram open while you work.

    Bazz Fuss stripboard layout: component side with every part and its holes, and the copper side showing the two track cuts
    ImportantThe copper side is a mirror image

    When you flip the board over to cut or solder, left and right swap. Column 1 is now on your right. The layout's copper-side view is already flipped for you, so use that view whenever the copper is facing up.

    The schematic shows the same circuit. It's useful when you check voltages or trace a fault.

    Bazz Fuss schematic: C1 into the base of the QA and QB Darlington pair, D1 from collector to base, R1 to +9 V, and C2 to the volume pot

  5. Cut the tracks

    Two holes need their copper cut: C10 and D6. Cut the tracks before you install any parts.

    1. Mark the cuts

      With the copper side up, find each cut on the copper-side view and mark it with a fine marker. Count columns from the right-hand edge, because the board is flipped.

    2. Cut each hole

      Place the drill bit in the marked hole and twist it by hand, with light pressure, until the copper ring around the hole is gone. You only need to cut through the copper, not through the board.

    3. Check every cut

      Set your multimeter to continuity. Check C9 to C11 and D5 to D7. Neither may beep. If one beeps, a sliver of copper remains: twist the bit again, or scrape the gap with a hobby knife.

  6. Install the wire link

    Install a short bare wire from B12 to C12. It joins QB's collector, on strip C, to the collector strip B. Solder both ends and trim the excess on the copper side.

  7. Install the resistors

    Resistors are not polarized. For each one, bend the leads to fit the holes, push it flat against the board, solder, and trim. Check each value with your multimeter before you solder it.

    ResistorValueHoles
    R110 kΩA2 to B5 (diagonal)
    R21 MΩD3 to E1 (diagonal)

  8. Install D1

    D1's band marks its cathode. Put the band end in C3 and the other lead in B1.

    If you're using an LED instead, the long lead (anode) goes in B1 and the short lead (cathode) in C3.

    CautionCheck D1's direction

    D1 backwards leaves the transistors with no bias, and the pedal is silent with the effect on.

  9. Install the capacitors

    1. Install C2

      Install C2 (100 nF) from C13 to F13. Film capacitors are not polarized.

    2. Install C1

      If C1 is an electrolytic, the stripe on its side marks the negative (−) lead, which is also the shorter lead. Put the positive lead in C4 and the negative lead in D4. A film capacitor goes in the same holes either way round.

      CautionCheck C1's direction

      An electrolytic capacitor installed backwards can fail and leak. Check the stripe before you solder.

  10. Install the transistors

    Install the transistors last, because they are the most heat-sensitive parts. Work quickly: about 2 seconds per joint, and let the part cool between joints.

    Both flat faces point right, toward column 14.

    TransistorHoles
    QAC in B8, B in C8, E in D8
    QBC in C11, B in D11, E in E11

    QA's emitter feeds QB's base through strip D. That makes the pair act as one high-gain Darlington transistor.

    CautionCheck the pinout of your transistors

    When you look at the flat face with the leads pointing down, a 2N3904, 2N2222, or BC337 reads E, B, C from left to right. A C1815 or S8050 reads E, C, B. With an E-C-B part, bend or rotate it so each lead still lands in the hole the table gives for that lead. Check your part's datasheet if you're unsure.

  11. Attach the off-board wires

    Solder a wire into each pad below from the component side, long enough to reach its part in the case. Leave some slack.

    PadGoes toSuggested color
    A12Battery snap +Red
    A14LED resistor, then the LED's long leadRed
    D1Footswitch lug 2Green
    E4Input jack sleeveBlack
    E7Footswitch lug 1Black
    E12VOLUME lug 1Black
    E14Output jack sleeveBlack
    F11VOLUME lug 3Blue

    Pot lugs are numbered 1, 2, 3 from left to right when you look at the back of the pot with its lugs pointing up.

  12. Wire the footswitch, jacks, and LED

    The footswitch wiring is the same as the Fuzz Face kit's. Its diagram shows Fuzz Face hole names, so use the pad table above for the board end of each wire. Select the diagram to open the full-size image.

    Footswitch wiring: the 3PDT switch's nine lugs, seen from the back, wired to the jacks, LED, battery, and board pads (Fuzz Face hole names)

    1. Check the footswitch

      With your meter on continuity, check that each middle-row lug beeps to exactly one outer lug in its own column. Click the switch and check again: it should now beep to the lug at the other end of the same column.

    2. Wire the footswitch

      • Lug 5 (middle) to the input jack tip.
      • Lug 6 (middle) to the output jack tip.
      • Lug 3 to VOLUME lug 2.
      • Lug 8 to lug 9: a short bare jumper. This is the bypass path.
      • Lugs 1 and 2 already have wires from the board. Lug 7 stays empty.

    3. Wire the LED

      Solder the LED resistor to the LED's long lead (anode, +), and the wire from pad A14 to the resistor's other end. Solder a wire from the LED's short lead (cathode, −) to footswitch lug 4. Cover the joints with heat-shrink tubing.

    4. Wire the battery

      Solder the battery snap's red lead to pad A12. Solder the black lead to the input jack's ring lug, not to the board. A mono plug in the input jack connects the ring to the sleeve, so the pedal only draws power while a cable is plugged in.

  13. Verify the build

    Before you connect a battery, inspect and test the assembly.

    1. Inspect the copper side

      Check every joint. Joints should be shiny and smooth, with no solder bridging two strips. Most stripboard faults are a solder bridge or a missed cut.

    2. Check for a short

      With no battery connected, measure the resistance between pad A12 (+9 V) and any hole in row E (ground). It must not read close to 0 Ω.

    3. Check the polarized parts

      Check D1's band (or the LED's short lead) is in C3, C1's positive lead is in C4, and both transistors' flat faces point right.

  14. Check the voltages

    The Bazz Fuss has no bias trimmer: D1 sets the bias. Connect the battery, plug a cable into the input jack, and put the black probe on any hole in row E. With no guitar signal, measure:

    PointWith a 1N4148 (simulated)With an LED (simulated)
    Strip A (+9 V)About 9 VAbout 9 V
    Strip B (collector)1.2 to 1.6 V2 to 2.6 V
    Strip C, columns 1 to 9 (QA's base)About 1.2 VAbout 1.2 V
    Strip D, columns 7 to 14 (QB's base)About 0.65 VAbout 0.65 V

    Real transistors and LED colors move these by a few hundred millivolts. If a reading is far off, see Troubleshooting.

  15. Test it

    Connect your guitar to the input and your amplifier to the output. Start with the amplifier quiet.

    • Click the footswitch until the LED is off. You should hear your clean guitar.
    • Click again. The LED lights and you should hear the fuzz.
    • Turn VOLUME through its full range.

  16. Mount it in the case

    Mount the footswitch, pot, jacks, and LED bezel, and tighten their nuts. Put standoffs or insulating tape on the copper side of the board, then fit it in the case. Place the battery where its terminals can't touch the board or the switch lugs. Close the case and test again.

    CautionKeep bare metal off the case

    If you line the case with foil tape, any bare lead or joint that touches it causes a short. Ground the foil with a wire to any free hole in row E.

Operating Instructions

The Bazz Fuss is a one-knob fuzz. VOLUME sets the output level; the amount of fuzz comes from your guitar's volume knob and how hard you play. The footswitch switches between the effect and true bypass, and the LED is lit when the effect is on.

The pedal runs on a 9 V battery and draws power only while a cable is plugged into the input jack.

Troubleshooting

  • Bypass works, but there's no sound with the effect on: check that the guitar goes into the input (stereo) jack. Then check D1's direction and the B12 to C12 link.
  • Collector (strip B) reads close to 9 V: the transistors aren't conducting. Check their pinout and direction, and check D1.
  • Collector reads under 1 V: look for a solder bridge from strip B to strip C, or a short to ground.
  • Very quiet or thin: check that C1 is at least 1 µF, and check the cuts at C10 and D6 again.
  • The LED doesn't light: the LED is probably backwards. Its short lead goes to footswitch lug 4.