This piece incorporates two different circuits.
One is an echo, the other a voice changer.
Both are taken from children’s megaphones.
The echo circuit is very similar to the one found in the barbie karaoke machine.
The VP-01 can be used as an FX processor AND as a sound generator. Both circuits generate noise when the pitch is lowered. The echo is especially noisey and creates pulsing blips and beeps at low pitches.
The layout is fairly straight forward.
The input signal is split out to both circuits. There is also an adjustment for sending the echo into the voice changer.
I rewired both circuits to add pitch adjustments and volume.
I’m currently working on a new version of the VP01 built from scratch. I’ve found ICs very similar to those found in the megaphones.
This model will be more versatile and reliable since it won’t be built from modified children’s toy circuits.
The echo IC is the PT2399.
Here is a link to a schematic for building an echo pedal using this IC.
There are more schematics and PCB layouts floating around if you look.
The voice changer IC is the HT8950
The only details I’ve found on this IC are the ones included with the spec sheet.