Hi there Storm
There's a PDF manual bundled in the zipped download for the Tessla Pro - I always extract these zip files to a new folder to keep all this stuff together!
Anyway, here's what it says in the manual about the controls:
BASS – increase or decrease the bass response
DRIVE – alters the gain amount of the signal into the processor
BOOST – adds further 12dB gain
TRANSIENTS – turning clockwise lets transients pass through
POWER – plug-in on/off
OUT – output level
Hope that helps
Steve