Hello! We are hoping to trial various external ultrasonic microphones with the new AudioMoth this field season and were wondering what people have for recommendations for microphones? We will be using the devices to record bats in California. Thank you for any input!
A while ago I suggested hooking up an SPU0410LR5H-QB with just a simple resistor to steal some power from the mic/bias pin. I have the feeling the load of the microphone is not enough and we need to create a little voltage drop in order to lower the bias voltage. Otherwise the audio might not pass through the microphone switch circuit. If you tied and found it was not working, try to add a 10k resistor over mic and gnd connection. (10k is not critical, a higher value might be a bit better for less influence on the audio)
Oh, and if I ever did sent any of you a 7mm round PCB with SPU0410LR5H-QB microphone on it, it probably has 1nF capacitors and no 1uF capacitors. 1nF creates a highpass filter effect so these only work on ultrasound. Sorry for that mistake. (8mm round versions were fine)
It would be nice to have the schematics, it looks like there is a SN74LVC1G3157 SPDT switch or something similar to switch between internal and external microphone and a MAX4466 opamp to amplify the audio. The small finger on the jacklug socket seems to connect directly to the switching line of the SPDT switch. Somehow it seems that U5 could be switching the power for the external microphone, but I can not see how what is actually switching U5, or maybe I just got confused switching back and forth between layers.
Thanks Alex for getting back. That's a shame that the 1.2.0 schematics haven't been released yet. I think that I would need these to ensure the work on an external microphone for bat recording is done properly and consistently between the versions. Is there a plan to release these at some point?
No, we haven't released the 1.2.0 schematics yet.
Many thanks Alex. Are the schematics for the 1.2.0 available anywhere? I have found a copy of the schematics for 1.1.0.
Hi Stuart, Yes, the analog circuitry is identical between 1.0.0 and 1.1.0. Both very different from 1.2.0 though. Alex
Does anyone know if the analog input circuitry is the same with the older 1.0.0 as the 1.1.0? I think that I am safe with testing that I am doing with external microphones with the 1.1.0 (the 1.1.0 schematics are available), but don't know about the 1.0.0.