4HP transistor ring modulator with AC/DC modes. Multiplies two signals for metallic, bell-like, and experimental timbres.

The standart (AC/DC) precisely designed transistor ring modulator.
This device multiplies two incoming signals, which gives a special timbre coloration to the sound.
At the heart of device is the strong transistor schematic which have maximum analogue sound.

Transistor sound
AC and DC modes
The panel is made of 1.5 mm thick aluminum (2mm in new models)
Size – 4hp

https://oiiiaudio.com/products/transistor-ring-modulator