Low Noise Balanced Microphone Preamp

Published:2012/10/29 0:51:00 Author:muriel | Keyword: Low Noise, Balanced Microphone Preamp | From:SeekIC

The input stage is configured for least noise and this has meant a non IC approach. There are some special ICs that can be used for mic pre-amps, they contain a circuit like this one except fabricated on one chip. Examples include the SSM2017 (now obsolete) or the replacement INA103 or similar. Components should all be readily available except for the 10 k ohm pot for the gain control. This needs to be a reverse log taper - or else use a multi-position switch with 6 dB gain steps covering the 60 dB range of the circuit. Make sure it is make before break. Editor's Note - Alternatively, a standard log pot can be used, but wired backwards . This will work fine if it is labelled Attenuation instead of Gain . As the pot is advanced clockwise, the gain is reduced (attenuation is increased). Maximum gain will therefore be applied when the pot is fully anti-clockwise. Note that this is not a problem that is specific to this circuit - all the IC mic preamps have exactly the same problem.



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