This module improves the volume response of the Etherwave Pro. Original Etherwave Pro theremins have what is called a snappy response. The softest audible sound is already quite loud, as silence is followed by a jump in volume from zero to a starting level of about -40dB. The consequences are not only a reduced dynamic range but also the impracticality of sophisticated expression at very low volume.
Please note, the EPVM1345 module does not function on the Etherwave Standard and Etherwave PLUS theremins.
Detailed information can be found on the website of the developer of the module, Thierry Frenkel: http://theremin.tfrenkel.com/chaudron/epvm1345