Guitar Pedal Circuitry

Nailing the perfect guitar tone is an abstract goal that's hard to quantify, but one can at the very least attempt to do so by understanding how different circuit components affect the sound of your instrument.

The following have the biggest effect on your tone:

1. Clipping - how much the top and bottom end of the signal is squashed and what shape it takes on the waveform.

   • Hard Clipping
   • Soft Clipping
     • Asymmetrical Clipping
     • Symmetrical Clipping

2. Equalization (EQ) - How loud or quiet a given part of the frequency spectrum is.

   • Boost - Increasing all or part of the signal.
   • Cut - Decreasing part of the signal. Is often referred to as attenuation.

3. Mixing - Mixing different signals, be it fuzz, high gain with clean, etc.

Humbuckers

EMGs use copper coils that connect to different parts of the preamp stage built into them to produce their sound, and use a smaller humbucker internally, about the size of a firebird pickup, with a solid magnet piece across. This results in a pickup that is less sensitive to interference and has a lower noise floor.

Fishmans use stacked PCBs instead of copper coils to design their pickups, which lets them control which parts of the pickup they can turn on/off to get a single coil/alinco sound with the different voice options.

Currently the state of the art in commercial pickups appears to be Fishmans, due to their dynamic nature allowing for controled voices.

Components

Resistors

Resistors typically function as low pass filters within a given circuit, which can be desirable at different stages of a circuit to say, cut the lows for a more punchy distortion.

Capacitors

Capacitors typically function as high pass filters, making certain frequencies louder, which can be useful when shaping the tone of your sound.

Transistors

Transistors are the primary way to generate a classic fuzz sound, with very hard clipping on your input signal.

Big Muff Pi has 4 transistors.

Diodes

Diodes limit the signal at various peaks, which serve to help soft-clip your signal.

The number of diodes heavily influences the sound, and how they're laid out.

• Asymmetric clipping

• Symmetric clipping

1. 1N5187 - Diode 200 V 3A Through Hole B, Axial Schottky diode, DO-41

Integrated Circuits

Amplification and voltage regulation - usually doesn't cause a strong difference in tone, but does affect volume and can offer some clipping with boosted signals:

Some of the most common are:

1. TL072 - Dual JFET-input op amp https://www.ti.com/product/TL072 - Tube Screamer

2. TL074 - Quad JFET Operational Amplifier - Amptweaker Fat Metal

3. TL082 Dual JFET Op Amp - Earthquaker Plumes

4. OP275 - Dual Bipolar/JFET Audio Amplifier - Mad Professor Honey Pedal

5. JRC4580D - NJM4580D by Nisshinbo Micro Devices - dual op-amp, DIP8 - King of Tone

There's also voltage regulators, often used to increase the voltage of a given circuit to affect the output tone.

6. LM108 - LDO Voltage regulator IC - RAT

7. TC1044SCPA - Switching Voltage Regulators

Interesting Pedals and Brands

• Eldritch Blast

• Black Fountain

• Acorn Amplifiers ADHD Synth Fuzz

• Kernom Ridge - the addition of controllable clipping, pre/post EQ, and mixing means this pedal can be a Klon, a Tube Screamer, and everything in between.

• Lichtlaerm Gehenna

• Amptweaker Tight Metal

More Resources

• PCB design communities such as:

  • Pedal PCB - A large catalog of PCB layouts for clones of a variety of pedals, from Klons to Tube Screamers, Delays, and everything in between.

  • Aion FX - Similar catalog

  • PCB Guitar Mania

  • Deadend FX

  • KiKad

• Wampler Pedals - How To Design An Overdrive Pedal Circuit

• Sweetwater Boost, Overdrive, Distortion & Fuzz Pedals

• JHS Pedals How to Find the Fuzz Pedal You Need

• Understand Guitar Overdrive Pedals

• BasicPitch Audio to MIDI converter