Henretta Emerald Prince

 They say:

The Emerald Prince is a preamp circuit modeled after the famous Echoplex EP3 preamp.  The 2” x 2” box can squeeze its way onto any pedal board.  An Internal trimmer controls output volume, with just a touch of boost.  An internal bright switch toggles between a bright mode that provides clarity and a unique mid-range character and a dark mode that fattens the sound while maintaining punch and clarity.