AnsweredAssumed Answered

1701 input noise

Question asked by bruce on Sep 11, 2010
Latest reply on Sep 21, 2010 by BrettG

Whenever I connect an audio source to the input of the 1701 (this is not the evaluation card), I get crackling and white noise.  This happens with any audio source, but for testing purposes – I am using a battery operated CD player [so it is isolated from ground].  The 1701 circuit is also battery powered.

 

When there is nothing connected it is silent.  I have been looking at the circuit for a while trying to narrow the problem down and I believe the noise is current related.  The 1701 ADC is also current driven.  So I was wondering if you could check my input resistor selections and give me some advice.  Maybe my resistor settings are too low?  …And more prone to noise?

 

My input is 1Vrms [I decided to try to keep it at 1Vrms to get the full dynamic range of the ADC].  And my sampling rate is 192kHz.

 

I calculated that my ADC_RES = 3K and the Rin=500 Ohm.

 

Can anyone help?

 

Thanks,

Bruce

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