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ADAU1442 SPDIF output sample rate error

Question asked by Brettcoupe on Feb 29, 2016
Latest reply on Mar 2, 2016 by DaveThib

Hi

I have a ADAU1442 running as a slave to serial input 4 clock domain4 (TDM16) from another DSP IC(Master)

The ADAU1442 is running external XTALin from the master DSP at 24.576 mhz (not from xtal)

The ADAU1442 also has Serial 0-3 as ADC-DAC ICs (slave ICs).

 

The Start Pulse Bit is set to serial input pair 4.

I measured the LRCLK feeding the ADC-DAC is and its exactly 48K.  The CCLK out is exactly 24.576mhz (512xfs)

However , SPDIF output  should also be running at 48k. but it is running at 48.01k. More strangely is that any tone generator i add to the DSP schematic and output to the SPDIF runs at 92% of the programmed Tone frequency. IE a 500HZ sine generator measures 460hz on my test gear.

The same tone routed out the DAC channel measures correct frequency.

Note My test gear is accurate and calibrated. Its an Audio Precision (AP) unit.

 

Any Ideas why the SPDIF output is off frequency?

 

Thanks

Brett

 

Message was edited by: brett kelly

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