I would like to amplify a difference signal from two electret microphones.
I would like to use an instrumentation amplifier with dual supply (AD620 for testing, probably INA103 for the final product).
Using dual power supply close to the maximum rating e.g -15V and +15 V will allow higher gain, and higher gain will result in much higher CMRR. I need high CMRR because the common mode signal will be far more louder than the differential signal.
I'll use a factory calibrated instrumentation amplifier instead of a simple differential amplifier for the same reason.
In the environment where this will be used, there is only a (noisy) +12 V power supply. My idea is to use to DC/DC converters, create +15 V and +30 V, and use the middle point as a new ground.
Suppose that the whole circuit will be isolated from the common ground, what are the disadvantages of using 0, +15, +30 V instead of -15, 0, 15 V?
(The DC/DC converters can do at least 1000 mA, much more than I need)
UPDATE: modified the requirements to +/-5V for making the design simpler. Would this circuit work, or should I use 7905 instead of 7805? I'm not sure.