The Sunny Distortion is a one knob distortion (volume, the gain is set at full blast) based on the sound of the Sunn Model T amp, manufacturers by Russian company D-Sound.
Here’s the video by Shnobel.
This is a distortion pedal, based on Sunn Model T sound. Great way to get doom/sludge/stoner sound. Only one knob is volume. Another knobs is your guitar knobs. You can use it to reduce or increase gain and set up tone.