ecm mic preamplifier

This circuit is a circuit diagram of ECM Mic Preamplifier. A microphone amplifier that can be used with either Electret Condenser Microphone (ECM). Preamplifier has a dynamic range very well and can handle anything from a whisper to a scream, but must be careful to ensure that the equipment that aids the amplifier or tape deck is not excessive. In
ecm mic preamplifier - schematic

the original series, I used BC650C ultra low voice device. This transistor is now difficult to find but BC549C or BC109C a good substitute. Circuit is to stabilize itself and will set the still point at roughly half the supply voltage to the emitter of Q2. The following is a schematic drawing: In this circuit diagram, 1k resistor limits the current to the mic. This resistor should be increased to 2k2 if the supply voltage above 12 Volts DC is used and not needed if the Mic insert is dynamic. The first stage built around Q1 amplifier is run at very low collector currents. These factors contribute to a very high overall signal to noise ratio and low overall sound output. The Q1 emitter resistor is separated by 100u bring this up to stage. Voice responses measured from the amplifier in the whole load is shown below 10k. Please note that this plot was made by inserting mic signal is replaced by a generator. The second phase, built around Q2 is coupled directly, this minimizes the effect of phase shift (introduced by the capacitive and inductive coupling method) and achieve a flat output response from 20Hz to over 100kHz. Frequency response is measured across the 10k load resistor. Q2 emitter voltage is also eaten back to basics Q1 through resistive coupling. This is also biased againt ensure temperature stabilization effect. Q2 operates in emitter follower mode, voltage gain of this stage is less than unity, however, the...

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