Distortion from CS8405A

maczrool · 22nd November 2006, 04:50 PM

I have a CS8405A connected to an MP3 player at the DAC inputs inside the unit with MCLK, BCLK, LRCLK, SDAT. I am not sure of what the format going to the DAC is, but I have started with I2S. Using this, I get perfect sound up to a point, as the sound gets louder, it starts to clip. Does this mean I am getting more bits out of this MP3 player than the CS8405A can handle or that my DAC cannot handle the extra bits? It is my understanding that if I am getting intelligible sound at lower volumes, that I have selected the right mode. As the board I've built up is hardware configured for I2S I would like to know for sure that I'm using the wrong format for the CS8405A before hacking up the board.

Thanks,
Stuart

rfbrw · 22nd November 2006, 05:05 PM

What is the dac part number?

maczrool · 22nd November 2006, 05:15 PM

Thanks. The signals are coming out of a Music Keg MP3 player right from the pins of a BB PCM1748E. I am connecting the SPDIF output through a Sharp optical transmitter to an Apple iPod HiFi into its mini optical input. As I said, the sound is fine in quieter portions of songs, but louder portions clip.

Stuart

rfbrw · 22nd November 2006, 06:22 PM

Sounds like you might have the wrong format. The problem you describe is what one would expect if lsb justified data is mistaken for I2S or msb justified data.

maczrool · 22nd November 2006, 06:32 PM

The more I thought about it the more your suggestion makes sense. So the clipping is actually just MSBs being cut off in the CS8405A.

Thanks for your help!
Stuart

maczrool · 22nd November 2006, 06:40 PM

What would be the most logical choice to try as far as formats go given the clipping I was getting? My choices are left justified, 16-bit right justified, and 24-bit right justified. It looks like from the datasheet of the CS8405 that left justified includes the MSB earlier in the frame than I2S, so I am leaning toward this choice.

Thanks,
Stuart

rfbrw · 22nd November 2006, 08:19 PM

Assuming Music Keg is either the Kenwood C710 or the CX910, then is uses the Cirrus EP7312 and that means 16 bit samples which might change things a little. For example, assuming 32bit frames per channel ,if Left and Right Justified data are swopped there will be no sound and if Right justified and I2S are swopped the will be only a 1 bit overlap which might as well be no sound. I'd try Left justified as well.

maczrool · 23rd November 2006, 01:06 AM

Yes that's the Cirrus chip it has and left justified is what it needed- no more clipping!

Thanks!
Stuart

22nd November 2006, 04:50 PM	#1
maczrool diyAudio Member Join Date: Oct 2002 Location: Louisiana, USA	Distortion from CS8405A I have a CS8405A connected to an MP3 player at the DAC inputs inside the unit with MCLK, BCLK, LRCLK, SDAT. I am not sure of what the format going to the DAC is, but I have started with I2S. Using this, I get perfect sound up to a point, as the sound gets louder, it starts to clip. Does this mean I am getting more bits out of this MP3 player than the CS8405A can handle or that my DAC cannot handle the extra bits? It is my understanding that if I am getting intelligible sound at lower volumes, that I have selected the right mode. As the board I've built up is hardware configured for I2S I would like to know for sure that I'm using the wrong format for the CS8405A before hacking up the board. Thanks, Stuart

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22nd November 2006, 05:05 PM	#2
rfbrw diyAudio Member Join Date: Oct 2001 Location: .	What is the dac part number?

22nd November 2006, 05:15 PM	#3
maczrool diyAudio Member Join Date: Oct 2002 Location: Louisiana, USA	Thanks. The signals are coming out of a Music Keg MP3 player right from the pins of a BB PCM1748E. I am connecting the SPDIF output through a Sharp optical transmitter to an Apple iPod HiFi into its mini optical input. As I said, the sound is fine in quieter portions of songs, but louder portions clip. Stuart

22nd November 2006, 06:22 PM	#4
rfbrw diyAudio Member Join Date: Oct 2001 Location: .	Sounds like you might have the wrong format. The problem you describe is what one would expect if lsb justified data is mistaken for I2S or msb justified data.

22nd November 2006, 06:32 PM	#5
maczrool diyAudio Member Join Date: Oct 2002 Location: Louisiana, USA	The more I thought about it the more your suggestion makes sense. So the clipping is actually just MSBs being cut off in the CS8405A. Thanks for your help! Stuart

22nd November 2006, 06:40 PM	#6
maczrool diyAudio Member Join Date: Oct 2002 Location: Louisiana, USA	What would be the most logical choice to try as far as formats go given the clipping I was getting? My choices are left justified, 16-bit right justified, and 24-bit right justified. It looks like from the datasheet of the CS8405 that left justified includes the MSB earlier in the frame than I2S, so I am leaning toward this choice. Thanks, Stuart

22nd November 2006, 08:19 PM	#7
rfbrw diyAudio Member Join Date: Oct 2001 Location: .	Assuming Music Keg is either the Kenwood C710 or the CX910, then is uses the Cirrus EP7312 and that means 16 bit samples which might change things a little. For example, assuming 32bit frames per channel ,if Left and Right Justified data are swopped there will be no sound and if Right justified and I2S are swopped the will be only a 1 bit overlap which might as well be no sound. I'd try Left justified as well.

23rd November 2006, 01:06 AM	#8
maczrool diyAudio Member Join Date: Oct 2002 Location: Louisiana, USA	Yes that's the Cirrus chip it has and left justified is what it needed- no more clipping! Thanks! Stuart

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