The Medical Mic Preamp & Optical Compressor

Built for Christoph Leich

The Medical Mic Preamp is built within a beautiful 1930's piece of medical equipment made here in Berlin.  The idea behind the preamp comes from Christoph's desire to have a unit that could be useful in a number of different recording contexts but especially suited for bass guitar.  
The circuit uses a pair of tubes with a range switch that varies the amount of negative feedback while the gain controls the level.  An input and output transformer is used to interface with both modern and vintage equipment-- both line and instrument signals as well as microphones can be inserted.  The optical compressor is designed to be very transparent and includes a simple attack/decay switch for different speeds.