Introduction
For many guitarists, the bypass system in their pedals is an afterthought—just a mechanical switch routing the signal in and out. But for those of us who obsess over the finer details of our rigs, a relay-based bypass system offers a smoother, quieter, and more flexible solution. Inspired by the Incandenza Bypass by Demedash Effects, the Flexi-Switch system by EarthQuaker Devices, and MAS Effects’ open-source work, I set out to develop my own smart bypass system that integrates both momentary and latching functionality using an Arduino-controlled relay.
The Arduino is a versatile microcontroller platform that makes it easy to integrate automation into DIY electronics projects. With its simple programming interface and wide range of available libraries, it allows developers to control components like relays, LEDs, and sensors with minimal effort. In this project, the Arduino acts as the brain of the bypass system, detecting footswitch presses and toggling the relay accordingly. Its ability to differentiate between short taps and long holds enables the dual-function switching behavior, making it an ideal choice for implementing a flexible and responsive bypass system.
This three-part blog will document the why, how, and what of this project—from concept to implementation. In this first part, I’ll cover the design philosophy, why I chose a relay over a mechanical 3PDT switch, and the key challenges I’m working to overcome.
The Problem with Traditional Bypass Systems
Most guitar pedals use one of two common bypass systems:
True Bypass (Mechanical 3PDT Switch): Simple, passive, and reliable, but suffers from loud switching noise and potential mechanical failure over time.
Buffered Bypass: Keeps the signal active through a buffer, but can introduce tonal coloration and is always active, even when bypassed.
While a relay-based true bypass system still follows the core principle of true bypass, it eliminates the mechanical noise of a standard switch, offering a quieter and more durable alternative. Additionally, by using a microcontroller like an Arduino, I can introduce smart switching behaviors like tap-to-toggle (latching mode) and hold-to-engage (momentary mode) in a single footswitch.
Designing the Smart Relay-Based Bypass
The main goal was to improve upon traditional bypass switching by combining the best aspects of mechanical and electronic switching. Here’s the basic concept:
Relay Instead of 3PDT Switch:
A DPDT relay routes the guitar signal between bypass and effect modes.
Silent switching, no mechanical clicking.
Longevity compared to a physical switch.
Microcontroller-Controlled Switching:
Instead of a standard latching switch, a momentary footswitch is used.
An Arduino detects short taps vs. long holds, enabling flexible control modes.
Multi-Mode Operation:
Tap once → Latches effect ON/OFF (Latching Mode).
Hold → Keeps effect ON, releasing turns it OFF (Momentary Mode).
Mimics the feel of EarthQuaker’s Flexi-Switch but implemented in a DIY-friendly way.
Key Challenges & Considerations
As with any project, there are hurdles to overcome. Here are a few key considerations in the development process:
Power Handling: Most relays require more current than an Arduino can safely supply, so a transistor switch must be used.
Debouncing the Footswitch: Since the bypass relies on a momentary switch, proper debouncing ensures smooth and reliable switching.
Fail-Safe Design: If the Arduino fails or resets, the relay should default to bypass mode, ensuring the guitar signal isn’t lost.
Soft Switching for Audio Purity: Preventing pops or clicks in the signal path by ensuring smooth transitions.
What’s Next?
In the next part of this series, I’ll dive into circuit design and prototyping, breaking down the relay switching circuit, the role of the transistor driver, and how the Arduino code processes footswitch input. I’ll also discuss potential refinements, such as integrating an LED indicator for status feedback.
If you’re interested in smart bypass systems, relay switching, or DIY pedal builds, stay tuned! Part 2 will bring us one step closer to making this versatile bypass system a reality.