modulation Archives - EffDub Audio

Just got these boards in today and have begun the first prototype build. It’s an optical tremolo with both the audio path and LFO made from a single CD4049 CMOS hex inverter. Despite having it all function in a single IC, there is no LFO ticking in the audio. Two of the inverters are the audio path (input and output amplifiers), and three more inverters are arranged as a low-frequency oscillator. And the last inverter is unused (I may do another iteration later that uses this last inverter to add a bit of grit/drive).

There are three controls: Speed (pot), Depth (pot), and Triangle/Square (switch). The switch controls the wave shape of the LFO. Be default, the LFO products a VERY square output. To try to smooth this out as much as possible, I added a very large capacitor as a rudimentary low-pass filter on the wave. The result is pretty close to a triangle wave shape. And the switch allows you to choose which wave shape you want to use (obviously). There is also an LED to indicate LFO speed, and it is lit even when the pedal is bypassed. The pedal will be available with either a standard 3PDT mechanical bypass switch or with a relay-driven soft-touch bypass switch (modest upcharge for the latter).

I hope to have a demo video posted soon, and after that I plan to sell these primarily through a local music shop (who will ship pretty much anywhere), but I will also sell direct if someone would prefer that.

Pic of the mostly populated board:

Pedals for Sale

August 4, 2024August 4, 2024 effdub

Coming Soon: Tap Temp Optical Tremolo

I’m pleased to announce the first of a few pedals that will be hand built by me in small batches and sold as cheaply as I can manage. There are cheap Chinese pedals galore these days, but I want to try and get as close to I can to slave-labor prices but made in the USA. Think of it as “shabby chic” or maybe “bespoke” rather than old-school “boutique.”

Effects Projects

October 9, 2023August 4, 2024 effdub

The Wahscillator – An LFO-driven Filter

I always liked the original ROG Phozer’s base sound, but the LFO wasn’t really that useful at lower speeds. So I took the basic idea, which is the Tim Escobedo’s Idiot Wah + LFO, and kicked it up a notch. Instead of the Phozer’s input JFET buffer, I went with an op amp buffer, and since there’s an extra amp in the package, I also added an output buffer. The LFO is the Shoot The Moon tremolo. For the variable resistor element, just about any of the usual suspects will work: LED/LDR combo, vactrol, or even one of those optical ICs such as the H11F1. And that’s how the Wahscillator came to be. Read More

DIY Effects Info

April 9, 2023August 4, 2024 effdub

Is the Univibe a Phaser?

There have been many an online (and offline) argument about the nature of the classic Univibe pedal. Is the Univibe a phaser? Is it a vibrato? Or is it something in between or something altogether different? Read More

Effects Projects

March 3, 2023 effdub

Shoot the Moon Tremolo

The Shoot the Moon Tremolo is an optical tremolo originally based on the excellent Tremulus Lune circuit by 4MS/CommonSound. The audio path is similar, but the LFO has been simplified to three controls: Speed, Depth, and Shape (wave shape). The power supply section has also been overhauled to provide better electrical isolation between the LFO and the audio portions of the circuit, and both sections are physically isolated as well. The result is a dead-quiet tremolo that goes from triangle wave to almost square wave (that is, smooth to choppy).

There is also a Gain control so that the output of the circuit can be set for unity gain; or it could be used as a boosted tremolo, if desired. Additionally, with the Depth at minimum and Boost set to greater than unity gain, the circuit can be used as a handy-dandy op amp booster with no amplitude modulation at all.

Download the Shoot the Moon Tremolo file pack.
Contains: Schematic image, PCB layout image, legacy PCB build guide document with notes, and Eagle CAD files.

Effects Projects

March 3, 2023March 3, 2023 effdub

DuoVibe – Optical Vibe / Phaser Project

The DuoVibe is an optical vibe / phaser and is yet another expansion on Tim Escobedo’s “Wobbletron” circuit snippet first published in 2005 (which is also very similar to the basic phase shift stages in the classic Univibe circuit). I have done several iterations on this cool little building block snippet over the years, and I feel that this one is a nice compromise between simplicity and functionality.

The DuoVibe is a two-stage optical vibe circuit than can also cop subtle phaser tones. The LFO is modified from the Shoot the Moon Tremolo (itself derivative of the Tremulus Lune) and is capable of triangle wave and near-square wave output. The pitch bend in vibe mode is discernible but not capable of “seasick” wobble. With the depth cranked, you can think of it as a sort of “tremolo with pitch funk going on” kind of thing.

There is a Vibe/Phase Mode switch, the name of which indicates its function and purpose. This switch simply toggles a feedback filtering cap value, but is useful despite the simplicity. See the mods section in the downloadable file pack below.

Download the DuoVibe file pack.
Contains: Schematic image, PCB layout image, legacy PCB build guide document with notes, and Eagle CAD files.