Simple circuit diagram which is very low noise. In the circuit diagram in the design of circuits that consist of a combination of differential pairs of transistors with a common mode (floating) gain control connecting the emitters of the pair. The plural pairs of 2N4403 and BC549s far longer than one transistor. In the different circuits in and outside and therefore requires a balanced to unbalanced buffer to give the appropriate output for the next stage in the signal from the channel mixing desk. This is provided by high-performance op-amp differential gain stage, which can be a TL071 or similar IC of your choice. Stage has a profit of six or 15 dB and maximum input level is set about 1.5 volts RMS before clipping. This is the same with an SPL of 150dB typical over the microphone.Operation on the input stage circuit is configured to at least the noise and this is not to approach IC. There are some special ICS that can be used for microphone pre-amps, they include circuits such as this, except on one chip fabricated. All components must be available except for 10 k ohm pot to get control. This need to be a reverse log taper – or if not using the multi-position switch with 6 dB gain steps to cover 60 dB range of circuits. Make sure before making a break already. The + / -15 Volt power supply is too important, should be regulated and low noise. If the voltage regulator usually used ICS I recommend fitting a post filter consists of a 10 ohm resistor and capacitor 470 UF to remove all noise generated in the ICS. A 100nF capacitor (C6) should be installed as close as possible to the op-amp supply pins – a ceramic cap is recommended to cut the best performance on high frequency.
the source of Phil Allison
http://freecircuitdiagram.net/low-noise-balance-microphone-pre-amp-using-a-tl071.html
