From Voodoo Lab:

The Voodoo Lab Tremolo re-creates the buttery, seductive tone of a vintage tube amp tremolo. This is accomplished by using the same lamp and photocell assembly found in many popular vintage amps.
This pedal also features a slope control which lets you adjust the feel from a traditional soothing tremolo to a hard “machine-gun” stutter. Speed and intensity controls provide a wide range to include very slow and deep sounds. A volume control lets you cut or boost the output level. Now you can add warm, mind-bending trem vibes to any amp with the most versatile tremolo available.

Quick Features:

- Authentic lamp and photocell tremolo circuit
- Slope control for waveform tweaking
- Ultra wide range of Speed and Intensity settings
- Compact, pedalboard friendly size
- True bypass switching with LED
- Runs on a 9V battery
- Hand built in the U.S.A.
- 5-year warranty*