Envelope Filter · One-off prototype
Electric Cosmonaut
A hand-built, hand-painted envelope filter that reads your picking and answers back with a vowel-y, funky quack. Dig in and it opens up; ease off and it settles down. Built on the PedalPCB Duck Box Filter circuit and dropped into a starfield-orange box with a cosmonaut riding shotgun.
- TypeEnvelope filter (dynamic auto-wah)
- ControlsAttack, Decay, Blend toggle
- CircuitPedalPCB Duck Box Filter
- Power9V DC, center-negative
- ConditionBench-tested & fully working
- StatusAvailable - one of a kind
⚠ Fine print from the void tap to expand / collapse
Not guaranteed new, not guaranteed to be any specific “clone,” and not even guaranteed to be from this universe — it might be cursed. What it definitely is: hand-built, one-of-a-kind, and straight off my bench. It's worn out its welcome here and it's time it found a new home — imperfections included.
Hand-built and one of a kind — and I stand behind it. Stops working within 30 days → full refund or free repair (I pay shipping back to me); free repairs anytime after that. Full returns & repairs terms »
What it does
The Electric Cosmonaut is an envelope filter - a filter that sweeps in response to how hard you play instead of a treadle under your foot. Pick softly and it stays mellow; hit it hard and the filter snaps open into that classic funky, quacky, talk-box-adjacent voice. It's the sound of “wakka-wakka” funk rhythm, squelchy synth-bass lines, and cosmic bloops.
Like most envelope filters, it likes a healthy, hot signal to really engage - roll your guitar volume up and dig in to find the sweet spot. It gets genuinely unhinged in front of a fuzz: stack it before a Big Muff and you get glitchy, gated textures and near-infinite sustain that blooms as the filter opens. The controls are hand-engraved right into the enclosure - Attack and Decay on the knobs, Blend above the toggle - so the one-off is as much object as instrument.
Demo
Demo filmed by Onion Madder on the actual unit.
Controls
- Attack
- Sets how quickly the filter reacts to your picking - snappy and immediate at one end, slower and more vocal as you back it off.
- Decay
- Controls how long the sweep hangs on before the filter closes back down - short and stuttery, or long, swelling, and vowel-like.
- Blend (toggle)
- Flips how much dry signal sits underneath the effect - keep the low-end body and punch, or go full-wet for the most pronounced quack.
Under the hood
| Circuit | PedalPCB Duck Box Filter - an envelope filter design |
|---|---|
| Op-amps | 2× NJM4558 dual op-amp |
| Envelope | 2N5088 NPN transistor + signal diode (built with the 1N4148 alternate) |
| Enclosure | 125B, hand-painted - starfield orange with white speckle and cosmonaut artwork |
| Power | 9V DC, center-negative (standard pedal supply); no battery |
| Bypass | True bypass, 3PDT footswitch |
| Build | Hand-soldered and finished by Onion Madder - a one-off prototype |
What builders say about the Duck Box
Heads up: these are verified-owner reviews of the PedalPCB Duck Box Filter - the circuit this pedal is built on - collected from PedalPCB's product page. They're here to show how the design behaves and sounds, not as reviews of this specific hand-built unit.
“Very aptly named; it quacks like a damn duck!! Like most envelope effects, you need a second or two to dial it in depending on how hot your pickups are. Very easy build and sounds fantastic. I used the 4148 diode that is suggested as an alternative in the build doc. Works great.”
“Great pedal, especially with fuzz. I used a 4148 and it sounds great.”
“It seems to want a pretty hot signal before it'll quack even at its most sensitive. I like keeping my volume not maxed and use vintage-style pickups so it might just not be compatible with my setup.”
“You've gotta be playing pretty hard or the signal has to be pretty hot before it seems to ‘engage’. The build was great - easy, plenty of room for pots and switches and fits into the standard 3-hole enclosure.”
“Way better than expected. Sounds immense before a Big Muff, adds tons of cool glitchy textures and infinite sustain. Love it.”
Circuit design: PedalPCB Duck Box Filter. Enclosure art, build, and finish by Onion Madder. Reviews © their respective authors, via PedalPCB. “Duck Box” and “PedalPCB” are used for identification only and imply no endorsement.