ADAU1761: Single-ended line input (AUX) enough for a microphone?

Dany Question

Dec 22, 2010 00:00

Hello,

Both my differential PGA input are used for other purposes than microphone processing.

I need to plug an analogue microphone (from an iPhone headset, for instance) into the LAUX or RAUX inputs.

The amplification I can count on is max.6dB, through the MX1AUXG for instance.

Is this enough to process through the ADC and Sigma software?

Thanks for returns on your experience.

Regards

Dany

Audio Signal Processors

SigmaDSP Audio Processors

adau1761

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ADIApproved Reply

Dec 22, 2010 00:00

The gain required in the pre-amp before the ADC will depend on the sensitivity of the specific microphone you're using. Microphones with a higher sensitivity will have a higher output level for a given sound pressure, and therefore will require less pre-amp gain. However, for most microphones, +6 dB will not be enough to match the expected full-scale output of the microphone signal with the ADC's full-scale input, which will result in a lower signal-to-noise ratio in the ADC output.

If you are not able to use the ADAU1761's PGAs for your microphone input signal and must use the aux inputs, then you may have to look at using an external preamp before the aux input pin.

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Dany Reply

Dec 23, 2010 00:00

Hello JeradL,

Thanks for the advice!

Yes, I will foresee an amp of 20-25dB or even to 30dB, so that I am able to use the range of -12dB to +6dB that the chip offers on an AUX input.

This will increase my BOM, but I see that is the only way. The mike input is going to be able receive different types of mike, so that I am not in the position to know the audio level to expect exactly.

Thanks again.

Regards

Dany

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EZAdministrator Reply

Apr 29, 2019 00:00

This question has been closed by the EZ team and is assumed answered.

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