Preamps Microphone Mixer circuit
Choosing a good power amplifier is very easy but to choose the perfect microphone preamps is not easy, because the adjustment of sound pressure level (SPL) with volt level (dBu).
Matching microphones and preamplifiers requires proper research and measurement, so to do this does not depend on your budget – but on ability and experience.
You must determine whether the microphone under the worst conditions would overload the preamp stage preamp inputs and whether it will degrade the performance of the microphone sound material.
Most condenser microphones require phantom power in the range of 12-48 VDC, with many extending to 9-52 VDC, leaving only a very few who really need only 48 VDC. The reason is that the internal design of most use some form of current sources to drive the zener voltage (usually 5 volts, sometimes higher), which determines the polarization voltage and power electronics.
involves checking the details of the final selection range is enough to get the preamp you use, that there is overload or metering indicators to assist in organizing, that the pipe is compatible with your cable needs, and that the color does not clash with your tour jacket.
Preamp Input Overload
One pascal is the amount of pressure generated from the loudness level of 94 dB (94 dB SPL is written as). For example, a sensitivity rating of 20 mV / Pa tells you that when the sound of 94 dB SPL strikes the microphone element, it produces the output voltage of 20 millivolts.
This simple design has very low noise, for example, BC549s 2N4403 and far more linear than a single transistor. The circuit is differential in and out and therefore requires a balanced to unbalanced buffer to give suitable output for the next stage in the signal channel mixing desk. This is provided by the stage performance of the op-amp differential gain is high, which can be a TL071 or similar IC of your choice. This stage has a gain of six or 15 dB and set the maximum input level at about 1.5 volts rms before clipping. This equals an SPL of 150dB with a microphone is more typical.
There are some special ICs that can be used for mic pre-amps, they contain such circuit or INA217 SSM2017.
If the usual voltage regulator ICs are used I recommend fitting the post filter consisting of a resistor and capacitor voltage should be adjusted.
Do not forget to also determine the quality Microphone Preamps circuit, .. it means an expensive microphone is more nice clear voice