A Raspberry Pi 3 is used to benchmark the performance of a couple of micro sd cards that meet the A1 standard, along with a couple of usb flash drives. Results are compared with previous studies by others with non-A1 cards.
A contact microphone (piezo disc) needs a special preamp to prevent the attenuation or loss of low- and mid-range frequencies in the sound signal. There are some DIY and plug/play options available. I bought a couple of modules from Stompville and installed them into plastic jars for use in field recordings of everyday objects.
The EM172 is a small and highly cost-effective electret capsule that has high sensitivity, low self-noise, and can be built into various form factors, including those for stereo field recording. Internet references are provided for a simple circuit that allows it to run on phantom power. A Neutrik XLR connector can house the mic and related components. This configuration should adapt well to various strategies for acoustic separation in field recording.