Compressor

Dual tube magic! Using the same professional-grade techniques as the most revered, vintage, high-end studio compressors, the Black Finger delivers truly professional performance compression. Unlike other "tube hyped" products on the market, which use 9 to 50 volts, the Black Finger's toroidal transformer allows for a full 300 volts of swing, preserving the attack while providing the warmest compression imaginable. Fantastic sustain, and a must for any amplified acoustic guitar.

https://www.ehx.com/products/black-finger