Modulated Delay
I already own a few different styles of commercially-available delay pedals. I wasn’t sure that I could make one that would do anything beyond (or even equal to) what my current ones can handle. But in an effort to escape the monotonous nature of daily life, I talked to some people and did some poking around and realized that I could get one to be pretty weird without having to resort to “writing algorithms,” or whatever it is that makes digital delay go.
Delay used to be done with tape—a literal loop of audio tape where sounds would be recorded and played back slightly later to produce an echo effect. A lot of people loved the sound of tape delays, depending on the exact state of decay of the tape, but they were physically large and prone to mechanical issues. As technology progressed, tape was largely replaced by things like bucket brigade devices (BBDs; solid state delay chips) and later, digital signal processing. I have nothing against any of these, but I have a limited ability and interest in making anything that uses analog tape or code, and I don’t want to have to set up a Tor client to try to find legit BBD chips.
Fortunately, there’s an alternative. The finest part of every karaoke machine: the PT2399 echo chip. It’s digital, but is self-contained, and works well within an otherwise analog circuit. Depending on what else is in that circuit, it can also be made to go completely bonkers.
I almost wrote, “without further delay…” but there is clearly so much more delay.
Details
I was unclear on what “modulated delay” is, and I can’t tell how much of that was on me and how much was from Marketing Departments Gone Wild. I thought it was a modulation effect (like a chorus or whatever) that was being applied on the echoes, similar to the way that a shimmer reverb has an octave up effect on the wet signal. In this case, modulated delay quite different: there is an LFO (low frequency oscillator) that is changing the actual delay time. Anyone who’s used an analog delay (or digital approximation of one) has probably experienced that thing where turning the delay knob while its echoing will kind of smear the sound and change the pitch. The modulation in this circuit is essentially automating the movement of that knob.
The top row of knobs are the standard delay controls:
- LEVEL: The level of the repeats. The original signal is always passed straight through at unity gain.
- FEEDBACK: How long it will keep repeating. High values tend to result in “infinitely.”
- DELAY: The interval of time between repeats.
The second row is the modulation section:
- RATE: The frequency/speed of the oscillation.
- DEPTH: The oscillation’s amplitude.
When the modulation is turned all the way down, the pedal acts like a standard delay. There are a ton of PT2399-based delays out there (my Vacuous Reverb uses a Belton Brick, which is essentially three PT2399s arranged to approximate reverb), and at their core, they all share a particular character. As with so many pedal components, the PT2399’s inherent crappiness at its job is what makes it interesting. They have a limited ability to accurately reproduce the original signal, especially when pushed beyond the suggested usage on the spec sheet, and the compounding degradation of the sample is their calling card. When the modulation is engaged, it can go from a subtle vibrato to a pronounced warble to complete swirling chaos.
There is also a RUNAWAY foot switch. When RUNAWAY is pressed, it’s the same as turning the FEEDBACK knob all the way up, which immediately sends it into infinite repeats. It turns out that infinity quickly gets loud and potentially annoying, depending on exactly what was in memory at the time, so it’s also nice to be able to release the switch and stop it without fiddling with a knob. Additionally, there is an effects loop that allows other outboard effects to be inserted on the delay line. If I want to put a chorus on the repeats (like how I originally thought a modulated delay worked), I can, but I’m not limited to chorus. I can go full-on Pedal Inception with effects within effects.
Monotonous is yet another in a string of circuits designed by dylan159. It’s his Shallow Green Pelota, which is an original design released under a Creative Commons BY-NC-SA license.
Vital Stats
Sound
If all this pedal did was basic PT2399 delay, I’d still like it. The repeats disintegrate in a pleasing way, and it’s got a surprising amount of delay available. It is not, however, a basic delay, and the modulation makes it…something else. There are settings that are somewhat ridiculous (which I appreciate—I don’t need my pedals to be “safe”), but it’s also capable of a lot of subtle movement that manifests in ways that wouldn’t be easy to approximate by other means.
The following is not the best example of what the pedal does, but it is exactly what it made me do. It’s a couple tracks of Emomaster tuned to open D running through George Washington Slept Here, panned hard to either side, with the Coronacaster doing more melodic stuff up the middle. There is no modulation other than Monotonous Delay, and there’s barely even any reverb…all of that ambiance and effect is from modulated delay.
