We would like to use the Audiomoth as a recording platform for adapting some ultrasound microphones to it (the Bufo or Myotis from our Sonitor system) to get low-noise recordings.
I would like to know whether in principle, it is possible to de-solder the built-in microphone (or install a switch, simply) to connect another microphone (like the Knowles SPU0410LR5H-QB or Vesper''s VM1000) to the PCB even though those microphones' native sensitivity would be much lower than the built-in microphone's, around -38 dB.
Are the pre-amps on the Audiomoth strong enough to boost the signal to an acceptable level? If it worked, we would be keen to show that the Audiomoth can be expanded with this open-source mic system. We would like to show that in an upcoming new version of our aforementioned article for which we would be glad to get new collaborators involved.
I got SPU0410LR5H-QB connected to an external mic plug for electret of mics of a Raspberry PI audio card. I used scheme from Figure 26 from SiSonic Design Guide /https://www.knowles.com/docs/default-source/default-document-library/sisonic-design-guide.pdf . There were other schemes which I haven't tested or compared yet. I do not have currently latest version of AudioMoth with external mic plug, so I cannot test. But probably this wiring would work also with AudioMoth.
Hi Olli,
That is exactly the point 😊
We are planning to test the first boards next week. The boards will be circular 10mm (same size as electret) and prepared for selectable 2 or 3 wire connection.
Would be nice to hear more about that circuit, thanks. I do have one SPU0410LR5H-QB and just noticed that it does not work if you put it to a plug reserved for an electret mic.
I found a document https://invensense.tdk.com/wp-content/uploads/2015/02/Using-a-MEMS-Microphone-in-a-2-Wire-Microphone-Circuit.pdf which describes a conversion circuit for another MEMS model - maybe this is something to try.
We are working on a plug and play compatible circuit with a Knowles SPU0410LR5H-QB, does anyone have interest in such a board?
Thomas, you should contact me on my email. I have been working on that same project for a couple of years and have some insight I could share. Halmitchell@gmail.com
Thank you very much Hall for the response. I will order the latest version of the audiomoth and I will test with my microphones (EM172). I think it's worth it. My olympus LS11 and my sony PCM M10 give excellent results with the EM172. My idea is to be able to connect my parabolic dish to the Audiomoth to carry out night migration monitoring.
Thomas
Hey Thomas, not sure if they have done any testing with the EM272 or not. The primo mics are hard to source in the US and I found alternatives to the EM172. I have never come across a recording device that has 5 volt plug-in-power (which is the EM272 operating voltage-https://micbooster.com/datasheets/EM272.pdf). Most recorders with plug-in power output around 2-3 volts. That being said I have plugged a EM172 into a plug-in-power recorder and it worked but maybe not to its fullest potential. I prefer this mic element made by PUI Audio which is rated at 3 volts and has the same signal to noise ratio as the EM272 (https://www.puiaudio.com/media/SpecSheet/AOM-5024L-HD-R.pdf). This would also be more in line with the flu-in-power output capabilities. Hope this helps.
Hello, I would like to know if tests have been carried out with primo EM272 capsules (new version of EM172)? The note "Using AudioMoth with External Electret Condenser Microphones ", only mentions the EM258 capsules. The latter displays an operating voltage of 3V against 5V for the EM272. Could an EM272 capsule still work? Thank you very much, Thomas Zgirski
The note doesn't mention the PIP voltage value. Depending on the voltage supply of the PIP provided from the device, some electrets would work better than others.
Hi Kevin,
The application note is now available, check out our latest announcement with the link.
Andy
Hi Kevin, There‘s an application note coming out today to describe this. It is intended for Electret capsules. However, it would probably work with a MEMS microphone with the appropriate circuit. We’ll have a look at this option. Alex
Hi there, congrats on rolling out Audiomoth 1.2 with connectivity to external microphones!
However, it is unspecified what kind of microphones could be connected to the Audiomoth with the 3.5mm audio jack. I suppose, only Electret-condensed mics that need a voltage bias? Probably not MEMS elements?
Hi, It will definitely be later this year. We have the case coming out next, and then an update to the firmware to support triggering. We're ordering the final PCB versions for the external microphone this week and will be testing it over the next couple of months. Alex
Hi Alex, your post on twitter was really eye-catching. Do you have any news about the next Audiomoth with external microphone ?
https://twitter.com/OpenAcoustics/status/1185968565960220673
These are excellent news Alex, thanks! Could you disclose more information about what kind of interface (connector, solder pads) would be used?
Hi, The next version of AudioMoth which we are working on now and will hopefully be out early next year will support external microphones. In principle you should be able to modify the PCB to accept any microphone. Alex