Building a Custom Octave & Envelope Pedal
One of the most exciting aspects of running Hamilton Effects is the ability to create fully custom guitar pedals. Whether it’s an idea inspired by existing effects or something entirely new, I love collaborating with musicians to bring unique sonic visions to life.
Recently, I’ve been working on a custom octave + envelope filter pedal for a client. It’s been a deep dive into both analogue and digital methods for generating an octave-down effect, refining circuit design, and ensuring the pedal fits within the Hamilton Effects aesthetic—all while tailoring it specifically to the player's needs.
The Process: Working with the Client
This project started as a conversation about creating an octave-down pedal with a “squelchy” envelope filter effect. Through discussions with the client, we refined the concept, deciding that both effects should be individually switchable, allowing for greater flexibility. We also worked through different control layouts, balancing simplicity with versatility.
Initially, the client wanted an octave up and down, but after discussing the development time and budget, we focused solely on octave down. The design has evolved through various iterations as I’ve experimented with different circuit approaches, keeping the client updated throughout the process.
The Process: Octave Down Development
Originally, I explored fully analogue approaches using the LM393 (a comparator) and the CD4013 (a flip-flop IC) to generate the octave-down signal. These methods worked but had their limitations—mainly in terms of tracking accuracy and overall tone. After testing various configurations, I ultimately settled on using an Arduino-based approach to generate the octave effect.
The Arduino method allows for: ✔ Better tracking across different playing styles ✔ A more synth-like, OC-2-style sub-octave sound ✔ More control over filtering and tone shaping
One challenge of using the Arduino is that it doesn’t have a built-in DAC (Digital-to-Analog Converter). However, since my analogue approach was originally going to use a square wave anyway, I found that using the PWM (pulse-width modulation) trigger output worked just fine for generating the raw octave signal. The next step is to refine how it blends with the clean signal.
Right now, I’m at a stage where I’m happy with the octave-down sound, and the next step is to build the mixer section, allowing the clean signal and octave to blend smoothly.
Refining Controls & Features
The control layout has gone through some refinements as well. Initially, I was considering a tone knob, but after experimenting, I’ve decided to go with a toggle switch that selects between two tonal modes:
Fat Mode: A fuller, warmer octave-down tone
Subby Mode: A deeper, more foundational low end
Additionally, I’m considering adding a Sustain knob, which will control how long the octave-down note lasts. This works by adjusting the input gain into the Arduino, which helps sustain last longer but can also affect tracking, especially on lower notes. This allows the player to fine-tune the balance between sustain and tracking accuracy.
Envelope Filter – Inspired by the MXR Dyna Filter
While I haven’t implemented the envelope filter yet, the plan is to base it on the classic MXR envelope filter schematic. The idea is to create a responsive, dynamic filter that reacts to the player's touch, adding a “squelchy” character to the octave-down sound.
The final control layout will include:
Octave Blend: Mix between clean and octave-down
Fat/Sub Toggle: Adjusts the tonal character of the octave
Sustain: Adjusts how long the octave sustains
Envelope Sensitivity: Adjusts how much the filter reacts to dynamics
Wet/Dry Filter Mix: Controls how much of the effect is blended in
High-Pass/Low-Pass Toggle: Offers tonal variety
Footswitches for Octave & Envelope Filter: Allows independent activation
Aesthetic & Design – Fully Custom Graphics
The pedal’s look is just as important as its sound. Typically, Hamilton Effects pedals have a minimalist, vintage-inspired aesthetic, but for this commission, the client wanted a full-pedal graphic design rather than the usual small foil plate design. This meant rethinking the print process and how the graphics would interact with drilling and hardware placement.
I’ve ordered a test print of the design to check:
How the artwork translates to the enclosure
Colour accuracy & texture
Durability when drilling through it for pots, switches, and jacks
Once that arrives, I’ll evaluate whether this method works or if adjustments are needed before committing to the final build.
Final Thoughts & Commission Info
This project has been a great example of what’s possible when working on a custom build from the ground up. It’s involved problem-solving, collaboration, and a lot of time refining circuits to ensure everything functions exactly as the client envisions.
I’m still in the middle of the process, with the next steps being: ✔ Finalizing the mixer circuit for octave and clean blend ✔ Building the envelope filter section ✔ Testing and refining the final design
If you’re interested in a fully custom guitar pedal, whether it’s an adaptation of an existing design or something completely fresh, Hamilton Effects is open for commissions. Whether you’re after a specific tone, a unique aesthetic, or both, let’s make it happen.
Get in touch if you’ve got an idea for a pedal you’d love to have built!