Balanced microphone Preamp - battery powered


2017-02-06 3:07 pm
Hi all,

I’m looking around for a circuit diagram for a microphone preamp.
There are lots of designs around but I have some specific requirements:

Balanced input
Balanced output (if possible)
Variable gain adjustment (+- 40-60dB)
Pad switch (if possible)
Battery powered (single 9V or 2x 9V)
Primarily for use in live environments so studio type noise levels are not a must have.
Simple design that can be made on strip board.
(Possibility a small batch of PCB’s could be made overseas. I’d therefore need a layout in a compatible format)
Nice to have: A battery level LED: Bi-colour that indicates good/low.
Small overall footprint - similar to a large smart phone with a height of around 25mm/1"
Nice to have: low voltage phantom power

Searching around the web I’m a bit snow blinded by the designs but none seem to fit my spec.

Any pointers or thoughts would be welcome.
If you select a TL072. use the + and - inputs, pins 3 & 2 with suitable feedback for a gain of 100 as the front end and the other half to vary the gain that you require.
Employ a TC7660 to produce the -9volt supply from the single PP3 battery.
I get about 200hours of use on one PP3 battery.


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