reverb + ?

lo-fi spring reverb

caution: extremely lo-fi
honorable mentions in #PO10DIY contest 

PCB, extension spring, bone conductor, piezo disc, headphone jack, potentiomter, PLA, ABS, metal plate
Mar. 2025






i've always loved making beats and sounds on my PO-33, but it was missing one important effect: reverb! So I created my own mini spring reverb—probably one of the smallest around! (not thoroughly researched and pls don’t quote me:) )

using a bone conductor and a sliding piezo disc, reverb + ? adds some extra magic: slide the disc back and forth, and you'll create similar-to-flanger effect.  due to the nature of the short distance of spring, reverb + ? act more like a lo-fi shimmer.

the custom PCB clips onto the back of your PO, hooking up easily through the headphone jack. It shares power from the Pocket Operator's original 2 x AAA battery supply and therefore, no need for extra batteries. There's just one simple slider on the front for mixing dry and wet signals, matching the PO's playful style. All enclosures are 3D-printed in ABS and PLA, with accent colors to keep things fun.

reverb + ? expands musical possibilities for PO lovers :)
demo video
hero - 1
hero - 2
detailed view - pocket operator (PO) and potentiometer
detailed view - power cables
detailed view - exntesion spring attached to piezo disc 
detailed view - slider for effect control & output headphone jack
detailed view - bone conductor soldered to PCB & power shared from PO
detailed view - input headphone jack from p.o. , also used to fix PCB to PO
detailed view - reverb + ? seperated from PO
screenshot of TE’s website - honorable mentions