Portable Microphone Preamplifier. High headroom input circuitry with 9V Battery powered.This circuit is mainly intended to provide common home stereo amplifiers with a microphone input.source

This is a High Quality, simple design Stereo Preamplifier with Bass-boost.The circuit requires 20 to 30V supply.This preamplifier was designed to cope with CD players, tuners, tape recorders etc., source

This is a simple Phono Preamplifier circuit.It suitable for moving-magnet cartridges with passive high-frequency equalization.This simple but efficient circuit devised for cheap moving-magnet cartridges, can be used in connection with the audio power amplifiers shown in these webpages, featuring low noise, good RIAA frequency response curve, low distortion and good high frequency transients behavior due to passive equalization in the 1 to 20KHz range. The circuit requires ±18V power supply. source