Condenser Mic Preamp Circuits has a fairly simple construction, which is specific amplifier for condenser mic. In addition to simple, Condenser Mic Preamp Circuits has a very good audio quality. The power generated by this amplifier circuit is 0.5 Watt with 4.5 VDC power supply.
Mic preamp circuit is equipped with an audio amplifier that can be directly connected to the loudspeaker. Thus the amplifier is suitable for use in low power audio such as radio transmitters, radio receivers, intercom, walkie-talkie, and others.
This mic preamp circuits constructed by transistors T1 and T2. Resistor R1 serves to provide a bias voltage to the condenser mic, while potentiometer VR1 function for setting the gain.
So that the signal from condenser mic can be directly heard through a loudspeaker, then after the pre-amp boosted again by end stage amplifier based IC BEL1895.
IC BEL1895 is one monolithic IC designed specifically for low power audio purposes with very good quality. BEL1895 IC can deliver 1 Watt power at 4 ohm loudspeaker. Besides BEL1895 IC requires only 3-9V voltage so that it will work perfectly with battery use.
Coupling capacitor C7 will determine the resulting low-frequency response. Capacitors C9 serves as ripple-rejection filter. Resistor R15 and capacitor C13 are combined to eliminate output oscillation. While the C12 is useful for boot strapping function.
This amplifier preamp circuit works well for use as a low-power AM transmitter modulation, or intercom amplifier for simplicity to be built.