Many Bypass Switching Options
There are many variations in bypass switch wiring and in stompbox power connections. We will attempt to cover these variations on this page. Let’s start with the power connections for your stompbox. The most common power connections for stompboxes are covered in this Power Switching Article. Please read the article.
Here is a wiring diagram for a simple battery hookup. Note that the “B1” in the diagram is a battery connector (battery snap) with a red and black wire coming out of it. It has a 9 volt battery snapped onto it.
Here’s a wiring diagram for options of battery or DC jack power:
Bypass Switching (Not True Bypass)
The simplest form of bypass switching is a non-true bypass switching with a SPDT switch. This was used in a lot of the old stompboxes because SPDT foot switches use to be less expensive than DPDT or 3PDT foot switches.
Adding an LED to the non-true bypass switching requires a DPDT switch. Again, the input or output will be left in the signal path, depending on how you wire it up. Note that some designers put an input buffer outside the bypass so that the buffer was in your signal all the time and the “tone sucking” would be minimized. An example of a buffer in the circuit of a non-true-bypass stompbox can be seen in the original schematic of the Blues Breaker and in all Boss and Ibanez pedal schematics.
- Non True Bypass with LED, circuit input unbypassed
- Non True Bypass with LED, circuit output unbypassed
The simplest form of true bypass switching uses a DPDT switch. Here are two variations on DPDT true bypass switching.
It is possible to have true bypass switching with LED if you use some electronic switching for the LED indicator. This Article from the GEOFEX site explains how this is done. Here’s a wiring diagram for the Millenium 1 switching.
True Bypass with a 3PDT Switch
Here’s the information on True Bypass Switching with LED indicator using a 3PDT switch. Here are some variations on 3PDT switching.
- True Bypass/LED indicator battery only
- True Bypass/LED indicator DC Jack
- True Bypass/LED indicator battery only, input grounded
- True Bypass/LED indicator DC Jack, input grounded
Note that R1 in these diagrams is a “current limiting” resistor for the LED. The value of this resistor will vary depending on the type of LED used and how bright you want the LED to be. The value of R1 is generally between 1k and 8k2, typically 4k7.
3PDT Switch Positive Ground Circuits
Here are some variations of wiring PNP Positive Ground circuits with a 3PDT switch. The basic information about this can be found in Power Switching Article.
- True Bypass/LED indicator DC Jack For a PNP Positive Ground Circuit with a Negative-tip Power supply
- True Bypass/LED indicator DC Jack Input Grounded For a PNP Positive Ground Circuit This is the wiring that most General Guitar Gadgets Positive Ground stompboxes use.
- True Bypass/LED indicator DC Jack For a PNP Positive Ground Circuit With a Positive-tip Power supply. This is the way the Fulltone PNP stompboxes are done. General Guitar Gadgets Does Not Recommended this Positive-Tip wiring as you will need to have a positive tip wall wart hanging around, and it will eventually get plugged into one of your negative tip stompboxes and could cause some damage. It is inevitable!
Multi-effects Bypass Switching
Here is a diagram for switching with 2 effects in one box using 3PDT and LED indicators
How to use these Diagrams
Now that we have most of the variations covered. Lets look at how to use these diagrams in the projects on this site. Here are the steps to take:
- Print out the switching diagram that you want to use for your project.
- Print out the wiring diagram for the project your are building.
- Identify the Circuit board input and Circuit board output for the project circuit board. Note that many times the circuit output is actually the middle lug of the volume potentiometer.
- Note that many of the PCB on our site have resistor designated as “R1” (the “LED current limiting resistor”) (usually a 1k resistor) built into the PCB. In this case, you will hook the wire from the “L” pad on the PCB to the LED
- Use the print out of the diagram to hook it all up, ignore the wiring on the project wiring diagram if you are using another variation.
We regret that we cannot provide diagrams for each variation for each project on the site. Due to the huge number of variations this is about the best we can do.