DIY phantom power for a microphone
Phantom power is a method of simultaneously transmitting information and supply voltage through the same elements. Most often used in audio systems. Specifically in microphones.
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What is phantom power for a microphone
This method of transmitting information is mainly used in condenser microphones. Thanks to phantom power, microphones provide high-quality and natural sound and also provide greater sensitivity.
DIY phantom power for a microphone
Often, in the design of audio technical devices (for example, amplifiers and preamplifiers), it is necessary to include a phantom power supply in the structural diagram. It is necessary to power the microphone, and its main characteristics are noise filtering and stability. The basis for this block will be a multiplier circuit using diodes and capacitors. For audio devices, multiply by 4 is appropriate.
As can be seen from the diagram, the multiplier is powered by transformer Tr1. Then capacitors C1-C4 and diodes VD1-VD4 form a four-fold multiplier. The load for the multiplier is an RC filter (R1C5 and R2C6). After them, another one was added. But the active filter is LM317. In addition to the filtering function, it also performs voltage stabilization. After the filter, capacitor C7 is included in the circuit to prevent self-excitation of the circuit. Without this element, there is a risk of creating its own noise at the output of the circuit.
You should also say a few more words about the remaining elements of the circuit.
R5 is a variable resistor that regulates the output voltage. It is necessary so that the user can manually set the values at which the background will be minimal and the voltage will be maximum.
ATTENTION. Resistors R3, R4 and R5 can get very hot, so they should be taken at least 0.25-0.5 W in power.
VD5 is a zener diode that protects the amplification stage from voltage drops during charging of C7 or during incorrect adjustment of R5. This element protects the circuit from failure if its reverse voltage is no more than 35V.
