The CGS504 combines 2 functions in to a single module:

Preamplifier - for scaling external audio signals to EuroSynth audio levels

Envelope Detector - also known as an Envelope Follower and which extract amplitude information from complex audio waveforms. The resulting dc voltage often drives non-linear stages, such as voltage-controlled amplifiers or filters.

The Preamplifier accepts a wide variety of inputs:

Lo-Z In - accepts outputs from high-output microphones in the range 200 to 1000 Ohms (such as most electret microphones), with a sensitivity suited for close-miking applications such as instrument or voice pick-up.

Hi-Z In - accepts outputs from transducers such as guitar pickups and contact microphones. It is also suited for amplifying low-level signals from tape machines, tuners etc. Sensitivity for various microphones and audio sources can be adjusted over a very wide range using the Preamp's [GAIN] control (but note, it will not cut the gain to zero).