Balanced Input, Phantom Power and mic Preamp

[mrdjnash]

Hi there,

This board looks great, and I had a few questions I was hoping you could answer:

For our application we need to take in the balanced input from an XLR microphone (so a differential circuit is needed), which also requires phantom power (48v, very low current ~3mA). A programmable gain amplifier would also be needed to boost the mic input. Is there any way you could customize the board to provide these? We would be happy to commission this if required.

One other thing, the specifications say it captures 32-bit audio. However, looking at the pictures of the board it looks like you're using a WM8731 which according to the manufacturer's datasheet says it uses 24 Bit ADC and DACs. As such, even though data word lengths up to 32-bit are supported, the audio is still captured using a 24-bit ADC. Is that correct?

Many thanks in advance,

Derek

[flatmax]

Hi there,

The board customisation is a lot of work, you may want to look at the Octo board which provides TRS balanced connectors in one of its breakout versions. The octo also lets you make custom PCBs for the analogue breakouts which would allow you to create a phantom power board.

Regarding the bit depth, yes the wm8731 is a 32 bit codec - check the manufacturer datasheet again please.

[mrdjnash]

Thanks for the reply. Regarding the bit depth, this is straight from the manufacturer's datasheet:

"Stereo 24-bit multi-bit sigma delta ADCs and DACs are used with oversampling digital interpolation and decimation filters. Digital audio input word lengths from 16-32 bits and sampling rates from 8kHz to 96kHz are supported."

I think you'll find it's 24-bit sampling, as opposed to 32 bit. 32-bit is just an available word length used when sending the data between the codec and the host.

Link here: https://d3uzseaevmutz1.cloudfront.net/p ... 1_v4.9.pdf

[flatmax]

Oh yes, I see what you are saying. The fact that 32 bits vs 24bits is perceptually the same also counts

Matt