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About PCM5102A

Fai Chan
Intellectual 440 points
Other Parts Discussed in Thread: PCM5102A, PCM1861

Hi TI experts, 

I have some questions about PCM5102A as below, I appreciate your help. 

Fai~

In my system, there are different audio signal input to the system and using PCM5102A is an analog output terminal for headphone. 

Case 1: PC's headphone(SE) signal output to (ADC)PCM1861 without gain to generate I2S signal to the Amp & (DAC)PCM5102A. 

Question 1 : The Vrms from PC is 1.3V, and 5102A's output Vrms is 1.2xV, so there is about 0.05V ~ 0.1V different. is it normal ? or is 5102A supposed to generate the exact same Vrms level as the original level from PC ? 

Question 2 : Are the below scenarios caused by the LowPassFilter or the Anti-aliasingFilter or other reasons?. I want to reconstruct the analog signal precisely from 5102A which can (1) have same loudness as the original signal from PC. (2) maintain a clean signal in full range frequency.

  • Scenario A: Anti-aliasingFilter added for analog input to PCM1861, and a LowPassFilter added for analog output from 5102A.                                              Result : (1) the loudness from 5102A is about 50% weaker than the original loudness from PC. (2) the signal is not really good from 5102A's output in high frequency range from 10Khz to higher
  • Scenario B: When i took out the LowPassFilter from 5102A's output.                                                                                                                                           Result : (1) the loudness from 5102A become same as the original loudness from PC. (2) the signal is bad in high frequency range from 10Khz to higher.

Case 2: Using TI's USB-I2X board connected to PC as a soundcard to generate the I2S signal to PCM5102A

Question 1: same scenarios and results happen as above Case 1's question 2_scenario A and B

*** The anti aliasing filter to PCM1861 and the circuit of PCM5102A (with LowPassFilter)  is show as below. 

*** The signal is shown as below ( Top is the original signal ) , (Middle is after 5102A with LowPassFilter) , ( Botton is after 5102A without LowPassFilter )