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ADC ADAU1978 TDM mode with DSP ADAU1452 - VR volume control THD issue

Question asked by Alvis on Oct 4, 2016
Latest reply on Nov 9, 2016 by Alvis

Hi all!

I am trying multi-channel setting, 

My testing enviroment :

ADC: ADAU1978, TDM mode (TDM16),

DSP: ADAU1452,

DAC: ADAU1962 (only one DAC)

Volume control: Variable Resistor(VR)


The TDM mode setting is alright, I can get the output and I want to use VR control the volume,

on adau1452 is my first time to use VR to control the volume  (last time I use software to control the vol.),

so I searched the forum, and I found this topic:

is talking about adc control volume, I use the topic volume block, like this:

after connecting the volume block, I use AP to test the THD, unfortunally, I got a bad value.

The signal through the volume block, the THD value is about 0.5 (too high).

If signal bypass the volume block (like picture, another radio button), the THD value is about 0.05.

So I guess the THD issue is at the volume block, the volume block setting like below picture:

so I want to ask, does anyone use VR to be a volume controller on the ADAU1452?

or any suggestion volume block which can use on the ADAU1452?