Guitar Pedal Prototype Board

The genesis of this project was the difficulty managing the various connections from the "real world" components (i.e., cables to and from the guitar/practice amp etc) to the various guitar pedal effect circuits being tested on breadboard, avoiding the "tangle" of cables on the workbench.

Similar to the DIY Electronics Development Board where it was observed that common "blocks" of hardware are typically required during project development, the same approach to testing and making guitar pedal effects was warranted. Any effect pedal has "standard" components such as the input/output jack connectors, various potentiometers, bypass switch, power supply etc. It is more convenient/efficient (and less error prone) to have them ready to "plug and play" rather than to re-wire on breadboard from scratch each time.

Of course with any "great idea" it probably has been done before, and such guitar effect development boards were available such as the "Beavis Board" (1), (2). Since these "Beavis Boards" are no longer available, this is the "home-brewed" version (which allows further customisation in any case, with the added benefit of utilising "bits and pieces" from the "junk box").

The Photographs and Video Sections demonstrate the rapid guitar effect pedal prototyping board, and also various stages of the construction. Schematics and circuit details are also provided in the relevant sections.

Switch SW1 enables 9V DC supply from the battery. Resistor R1 limits current to the power on LED indicator (D1).

Switch SW2 (two pole, double throw) enables directing the line-in and line-out signals to the breadboard, or connecting the line-in with the line-out (i.e., bypassing the breadboard/effect pedal prototype circuit).

Potentiometers RV1 to RV4 are wired to the relevant "quick splice" terminals, which in turn, allow connection to various points on the breadboard.

Switch SW3 (two pole, six throw) provides a means to connect various points/components on the breadboard to test possible modifications of the test circuit (e.g. different value capacitors, alternative diodes etc).

Z1 and Z2 are standard mono guitar 1/4" (6.35mm) input/output jacks (which with switch SW2 provide either input to the breadboard test circuit, or by-pass the test circuit.

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  Guitar Effect Pedal Prototype Board Schematic

This project did not require a PCB.

The construction was done using prototyping board. See the photographs and schematic diagram sections.

Initial testing involved checking the "effect on/bypass" function provided by switch SW2.

With switch SW2 in the bypass setting, strumming a guitar connected to the input port should be heard on an amp/speaker connected to the output port. Simultaneously, a multimeter connected across the "breadboard line" and "breadboard line out" (J3) should give an "open circuit" reading.

Closing switch SW1 should illuminate diode D1 (indicating 9V DC power supply from the battery is available). A multimeter connected across the wires from J1 and J2, with switch SW1 closed, should give a voltage reading of whatever is the current battery voltage.

Using a multimeter, the connections between the various potentiometers and the relevant terminal block connections can be tested (in resistance mode, should get the value of whatever potentiometer has been used in the circuit).

The actual power supply part of the circuit is relatively simple and no particular difficulties, other than the usual care and attention required when constructing any electronic circuit, should be expected.

I used a printed template (use whatever graphics or editing programme you have that is suitable) that provided the centers for drilling holes for components etc. Conveniently, this template then also provides the "decals" for the switches etc. After glueing the template onto the enclosure, I used 4" wide clear packaging tape to seal the surface (which also allows for writing component values/notations etc using a marker pen, that later could be removed/changed). The choice of enclosure is left to the builder.

I was not certain of which components to include with the prototyping board, so I choose to utilise a cardboard shoebox as the "temporary" enclosure. Not only did this enable easy construction (e.g. drilling holes and cutting access ports for various switches/components was easily done with a knife/blade), but this leaves considerable room for easy expansion after experience with attempting construction of a few guitar effect pedals is gained. Further, the shoebox interior provides a convenient storage location for parts/components associated with experimenting/making guitar effect pedals.

Another "design decision" is the use of connector/terminal blocks. Such connector/terminal blocks (see photographs section), inconjuction with "dupont" cables (or similar jumper leads) enable easy connection with the breadboard/circuit.

However, this is an additional expense (although such connectors are inexpensive on ebay) and the alternative of using wire leads directly from the components to the breadboard is practical. The downside being that when a particular component (e.g one of the potentiometers) is not being used in a test circuit on the breadboard, the wire leads will need to be "tidied" away. The use of "dupont" cables and quick-splice connectors makes for "clean" operation of the prototyping board, likely leading to less errors and time spent in debugging.

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