Appears to be a new digital theremin design floating around Amazon, eBay, and Aliexpress. Can be had for under $60 shipped - haven't seen too much discussion online yet. There's a video demo on the linked webpage, and another one on Aliexpress.
I chose a bad picture, there are jacks for both volume and pitch antennas.
Guessing Cortex M0+ STM32 or clone thereof based on the lack of visible chip markings on the microcontroller.
That said, if it turns out to be an Atmega328 we can probably assume they ripped off Open Theremin. Hope that isn't the case.
I'm an analog novice but I've definitely been curious about how far it would be possible to strip down the base theremin design with a solid understanding of modern low-cost ARM microcontrollers - for instance, could they be hacking the built-in capacitive touch processing hardware to reproduce the heterodyning? A lot of these Chinese gadgets also tend to be quite open and hackable, and usually showcase some interesting emergent digital design trends. Things like these tend to get even more interesting if you can figure out how to disassemble the firmware, or even convince them to open source it.
To be clear, I am expecting this to be unusable as a performance instrument, which is where my personal interests lie. That said, if the designers are clever, there's no reason this thing can't beat the Theremini, which is a slap in the face at $300, on every important spec at 1/5 the cost. Certainly at $60 it has higher potential to act as a 'gateway drug' for beginners.
I did order one from eBay and will share my findings when it arrives, perhaps there will be some nice easter eggs on the silkscreen. Looking forward to being more fun at parties.
