RK3308 Audio ADC

I was rather hoping to get the newer SoC revision of the RK3308-BS but got the older silicon but thought what the heck I will try the 4 mic channel ADC anyway.

What ever I seem to do with what might be considered ‘normal’ electret based bias circuits in terms of capacitors the gain seems very low but the noise levels are terrible with SNR of near 1:1
I am been using single ended circuit inputs and various capacitor values and not made any headway into the problem and just thought I would ask if anyone has actually managed to setup a reasonable signal on the ADC and how?

Have you turn off all radio device ? eg. wifi & bt.Try using low ripple power supply,eg. Linear power supply.

Turning off all radio devices negates its use as a SBC, also linear power supplies which I have tried and the noise is from the SBC not very expensive linear supplies complete out of the budget of a supposed mini budget SoC.

All the revisions up to 1.3 have huge noise problems that as far as I know no one has managed to use.
I was wondering if maybe it was fixed with BS edition chip as even Radxa dropped 8x ADC inputs to x4 because really they are pretty pointless.
Its been a rough ride for Radxa and the qty of revisions is testimony to this which is a shame as this is a pure audio SoC with a huge array of audio options and about the only thing that works is PDM input and I2S output.
Could of been hugely popular for Voice & Audio projects but seems to not work or at least the design we have doesn’t.
You can not get everything right every time and just one of those things.

Look this , I don’t think this board is suitable for voice-devel

Nope definitely not and such a shame for a SoC with embedded VAD, ADC, Codec and a host of audio interfaces to allow it.

You will find me lower down in the thread

Really you should be able to utilise the ADC as this evb board and have 2 spare ADC inputs so you can use as loopbacks to sync AEC algs.

The ADC maybe due to tiny design and not enough isolation on the audio just isn’t capable as whatever you do there is a huge amount of noise and turning of the radio just negates its use so isn’t a solution.