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ecm mic preamp

2017-08-16 20:48  
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This article is an introduction ecm microphone preamplifier. The microphone preamplifier ecm a microphone amplifier, you can use either the electret condenser microphone (ECM) inserts or dynamic inserts, with discrete components. The two transistors in the circuit should be low-noise type. You can choose BC650C, BC549C or can also be used  BC109C . This circuit is self-bias voltage and the quiescent operating point will set it at about half the supply voltage at the emitter of the transistor final electret condenser microphone (ECM) contains a very sensitive element and an internal microphone pre-field-effect transistor amplifier, the power supply in the range of 2 to 10 volts DC, is therefore necessary. The right of the ECM is also available from Maplin Electronics. 1 k resistor limits the current microphone. 2 k2 This resistor should be increased if the supply voltage exceeds 12 V DC is not used if the microphone into a dynamic. Output impedance is very low, suitable for driving distance of 50 meters telegraph. Thus it is not necessary for the shielded cable.ecm ecm mic preamp.html


The frequency response measured across a 10k load resistor is plotted below simulated using a 12V power source:

micbode ecm mic preamp.html

The noise response of the amplifier measured across the 10k load is shown below. Please note that this plot was made with the mic insert replaced by a signal generator.

micnoise ecm mic preamp.html

This preamplifier has excellent dynamic range and can cope with anything from a whisper to a loud shout, however care should be taken to make sure that the auxiliary equipment i.e. amplifier or tape deck does not overload.