Microphone support for Beagleboard XM

Hi Gerald,

I noticed the BeagleboardXM has been designed to use Line in for the
audio input which means users need to add some type of pre-amp for a
Microphone to work, I noticed these posts,

"The audio in jack on the Beagle boards is line level. Whatever mic
choose needs a preamp to get it up to that. You have to use MAX9812"

The BeagleboardXM uses a TPS6595C for audio, do you know if there was
any reason a standard Microphone was not supported?

The decision was made to support line in as the default. If you used a powered microphone it should work. We couldn’t really support both very easily using the one stereo jack.Stereo recording was deemed and important feature for the board. Line in was deemed a more standard feature and by using a powered microphone, that could be supported as well.


Thanks makes sense,

I just wondered if there was some issue with the Microphone inputs on
the TPS65950

Thanks Gerald


Not that I know of. They should work fine.


Hi BB audio guys,

For those who are interested in quality audio input for BeagleBoard: I am in the process of designing and building a board with the same form factor as the original BeagleBoard C4 and connecting to the expansion connector back-to-back.

The design is based on the AK5394 24-bit, 192 kHz ADC from Asahi-Kasei and the INA136 low noise microphone preamplifier (with 9 position manual gain setting (1 … 1000)). It further contains selectable +48 V phantom power for the microphone. From the differential microphone the conversion is simultaneously done for R and L channels. Software may then decide which conversion result is better or try to get another +3 dB S/N by averaging them. I am using the brand new fully differential TI OPA1632 opamp to drive the ADC.The rest is a processor readable 6-bit switch register for default configurations, a bright, processor controlled RGB LED for indications and the level shifters for OMAP3530.

Prototype boards and components are ready waiting for assembly, but my AES paper writing keeps me busy for another week now. I think I will have the assembled bords tovards the end of March.

If somebody has access to the Audio Precision AP-2 and wants to help to know if my design is any good, please let me know,