Electronics for Building Things · Lesson 28 · Guitar Effects on a Breadboard

Delay & Modulation

Time-based effects — echo, chorus, tremolo — and the chips that create them.

Boost, clipping, and filters all act on the signal instantly. Time-based effects are a different beast: they involve delaying or continuously changing the signal. These are more advanced than a distortion, so this lesson maps the territory and points you to the right building blocks rather than every detail.

The one win You understand how echo, chorus, and tremolo work in principle, and which chips and circuits you'd reach for to build them.

Delay: hear it again, a moment later

A delay stores the signal and replays it a short time later; feed some of the output back to the input and the echoes repeat and fade. Doing this in pure analog is hard — you can't easily "hold" a waveform with resistors and caps. Two technologies solve it:

BBD (bucket-brigade device): the classic analog approach — a chip that passes the signal through hundreds of tiny capacitor "buckets," each handing it to the next, so it comes out later. Warm, lo-fi, the sound of vintage analog delay/chorus.
PT2399: the modern hobby favorite — a cheap, through-hole chip that delays digitally (it samples the signal into memory and plays it back) yet sounds pleasingly analog. Delay times ~30–340 ms, runs at 5 V, very mod-friendly (ElectroSmash: PT2399 analysis).

Rule of thumb For a DIY delay/echo on the breadboard, the PT2399 is the go-to chip — well documented, forgiving, and surrounded by published circuits. It's an IC: give it power, ground, the datasheet's typical circuit, and a couple of pots for delay time and repeats.

Modulation: a slow wobble via an LFO

Chorus, vibrato, tremolo, and phasers all share one engine: a low-frequency oscillator (LFO) — a slow, steady wave (well below hearing, like 1–10 cycles per second) that continuously changes some part of the circuit:

Tremolo: the LFO modulates volume up and down → a pulsing sound. The simplest modulation effect to build.
Chorus / vibrato: the LFO modulates a short delay time (often a BBD or PT2399) → pitch wavers slightly, thickening the sound.
Phaser: the LFO sweeps a set of filters → the familiar whoosh.

Where this fits your journey

These are great next builds, not first ones — they layer an IC (PT2399) or an LFO on top of the exact fundamentals you now own: gain stages, coupling, bias, and filters all reappear around the delay or modulation core. Start with dirt (it's simpler and immediate), then graduate to a PT2399 delay or a tremolo once the basics feel natural.

Check yourself

Read this next (primary source) ElectroSmash — PT2399 Analysis for delay, and skim ElectroSmash's pedal analyses for modulation circuits.

I'm your teacher — ask me anything. When you're ready for your first time-based effect, tell me whether you want echo or wobble and I'll point you to a beginner-friendly circuit.