Erica Synths Black Spring Reverb offers a unique approach to spring reverb units. First, it features a built-in vactrol-based audio compressor; second, it can operate an external tank as well as a combination of both internal and external tanks for unprecedented effects; third, to animate the reverb effect, the module includes built-in feedback effects such as pitch shifters, delay, ring modulator, and more. The feedback amount and effect parameters can be controlled manually and via CV, making the module an experimental instrument in its own right. The module comes with a compact spring reverb tank that can be easily installed in most Eurorack cases.