Check the listing for details. Synthrotek Optical Theremin DIY Kit - Square Wave Light Sensitive 1/4 Inch Jacks. Condition: New. Listed at 24.99 USD. Let there be light!!!The Synthrotek Optical Theremin is one of our wildest circuits! Two optical resistors, sensitive to light shining upon them, control both the pitch and volume of a standard 555 timer in astable mode. The result: a chaotically cool noisemaker! Two potentiometers allow for setting levels and sensitivity of both optical resistors. The circuit is simple to build and powered by either a 9V battery or a 9V center negative AC adapter. Loads of fun and highly adaptable/modifiable, you’ll see the light with the Synthrotek Optical Theremin! Note that if you are using an AC adapter, it needs to be 9v center NEGATIVE. DIY OPTICAL THEREMIN KIT - Synthrotek.com w/ MicroMoog Moog Analog Synth - WOW! - YouTube Video will open in a new window Using the eBay App? Paste link into a browser window: