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Old 18th June 2012, 04:47 AM   #1
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Default Trouble with PCM2707 & WM8524

Hey everyone,

I know the PCM270X chips have been discussed quite a bit on here but I'm pulling my hair out trying to get my WM8524 to output "listenable" audio from the PCM's I2S output.

Basically, the WM8524 outputs a large amount of distortion that sounds nothing like the audio signal going into the PCM2707.

I've had the PCM2707 running using its internal DAC without problem for a couple weeks. I've now switched FSEL from VDD to GND indicating that I'd like the chip to output I2S. I have all 3 lines for I2S on the output of the PCM2707 scoped and they look good despite being built on a breadboard. The WM8524 is built on the breadboard as well and I have all three I2S lines as well as the system clock line running from the PCM2707 to it. The WM8524 has both the MUTE pin and the AIFMODE pin pulled high.

Current troubleshooting thoughts:
1. Should I be using the system clock output from the PCM2707 for the WM8524 or should I use the 12Mhz external clock oscillator on the board?
2. I am using a single supply from USB to power all supplies on the two chips. Is there a possibly that the charge pump circuitry internal to the WM8524 could be causing noise on the supply that is causing problems?
3. My other concern is that all the bypass caps required for the WM8524 are not close enough to the chip itself. This is because the chip is on a DIP adapter board for use on my breadboard. Could this be a problem?

Any ideas?
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Old 20th June 2012, 02:22 AM   #2
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Anyone wanna take a stab at it? I wonder if this should be moved to the "Digital Line Level" forum.
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Old 20th June 2012, 03:23 AM   #3
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What are you putting the output into to listen to?
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Old 20th June 2012, 05:38 AM   #4
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Quote:
Originally Posted by Redshift187 View Post
What are you putting the output into to listen to?
I've tried the output of the WM8524 with headphones and with a home audio receiver. The datasheet does indicate that the min load impedance should be 1K and so the headphone test was secondary.

Last edited by Killjoy99; 20th June 2012 at 05:54 AM.
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Old 20th June 2012, 06:12 AM   #5
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Can you post your schematic(s)?
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Last edited by Redshift187; 20th June 2012 at 06:14 AM.
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Old 21st June 2012, 05:29 AM   #6
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Here is my schematic. VCC is a 3.3V low noise regulator.
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Old 21st June 2012, 05:58 AM   #7
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Everything looks right to me. I would try pulling Mute low, start playing something, then bring it back high. If that works, maybe try tying it to Sspnd on the PCM2707.
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Old 9th October 2012, 10:40 AM   #8
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did you fix your problems? I would like to develope the same circuit and I want to know if the schematic is right or not.
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