This is a simple microphone preamplifier circuit board from Sparkfun PRT-08872 for a wide range of microphone types, with good pre-amplification to attach to your larger stereo amplifier. This circuit is suitable for use with normal stereo amplifier line/CD/aux/tape inputs. The microphone preamplifier works great with guitar pickups, piezo disks, and can take both dynamic and electret microphone inputs (preamplifier provides power for electret microphone elements). This is a simple, easy to build circuit that is flexible and very handy when working with microphones and amplifiers.

Board does not come assembled. You will need to purchase the components separately which are available from Technobots:

R3 4.7 kohm
R4 220 kohm
R2 2.2 kohm
R1 120 ohm
C1, C2, C3 & C5 10 uF 16V electrolytic
C4 100 uF 16V electrolytic
D1 Red LED
Q1 BC547B
SW1 on/off switch

Features:

* Very simple one transistor circuit
* Amplification 35 dB, flat frequency response from 20 Hz to 20 kHz
* Low distortion but certainly not studio quality
* Interface dynamic or electret microphone to a line level audio input in HIFI amplifier or computer soundcard
* Power supply: 9V battery, takes less than 10 mA current
* No special protection circuits used
* No special electrical safety considerations

Dimensions: 25 x 38 x 15 mm

Further information can be found at this site