This microphone circuit is originally designed for recording sounds from very far distances using microphones with parabolic
reflectors. Its noise level is around 7 dB and has a distortion factor of around 1%. This value is less than the distortion factor of a
tape recorder. A 130ÁV input signal gives an output level of 60mV. This figure shows that the microphone amplifier is very sensitive.
The amplification factor is around 475. The circuit can also accept input levels up to 8mV. Its bandwidth is from 20 Hz to 45 kHz.
Coil L1 is several turns of magnet wire in a ferrite core. This mic amplifier is about 12 dB better than the mic amp of a good tape recorder.
Of course, this circuit can also be used in standard music recording. The quality of the recorded music is much better than the one recorded with an ordinary amplifier.
The resistors used in this circuit are of metal film type to obtain the best results.
Printed Circuit Layout
Parts Placement Layout
Electronic Circuits volume 1.0 - Circuit Nr. 3
The complete data of the electronic circuit described above can be found in the following book and is available from Amazon.com.
Click on the image to view the book.