I'm looking for somebody who can design 2 working preamp circuits with an included switchable AGC (or compressor), a switchable high pass filter and < 18 V working voltage (possibly from a single battery source, ideally 4x Li-ion batteries 3.7 V).
I already have the basic preamp schematics, they should just be merged with the switchable AGC (or compressor) and switchable high pass filter.
One circuit is based on a piezoelectric transducer and the other on a electret condenser microphone array.
Noise and distortion should be very low since most sound sources will be very faint (animals field recording, with equipment left in the field for days before being retrieved). I think that IC used in these are already reasonably low but feel free to switch to others with better performance (unless they're too difficult to get, since I'd order the parts and build them by myself).
I have an eval-board of a sigma-dsp "EVAL-ADAU1701MINIZ".
The function is "configured" with the graphical design software within let´s say 15 minutes. And some seconds later you can test the result.
Mostely drag and drop style placing icons ....a couple of connections and a little setup.
There are cheap ADAU1701 boards available at ebay.
I did not check if the DSP meets all your specifications.