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PCM4222EVM: Noisy 96 khz

Chris Ash
Prodigy 50 points
Part Number: PCM4222EVM
Other Parts Discussed in Thread: PCM4222

Hi there,

I have this 4222 evaluation board that works perfectly at 44.1khz. No noise, sounds amazing. At 96khz sample rate there is noise without anything plugged into the analog inputs, similar to pink or white noise. I believe my settings for clock and all the rest are correct, and am open to anything to try next on this.

Thanks a lot,

Chris

  • 0
    TI__Guru**** 174821 points

    Hi Chris,

    Welcome to our e2e forum!  Can you tell us how you have the switches and jumpers set on the PCM4222EVM?

  • 0 in reply to Tom Hendrick
    Prodigy 50 points

    Hi Tom,

    Thanks for the welcome! And thanks so much for taking the time to help with this. I'll consult the info sheet another time in case I've made an error. Here's how I have everything set so far for 96Khz operation.

    SW1 -------------

    DSDMODE  LO

    MODEN  LO

    DSDEN  LO

    DF  LO

    FS1 LO

    FS0  HI

    HPFDL  LO

    FPFDR  LO

    PCMEN  HI

    SW2 -----

    SUB0 LO

    SUB1 LO

    SW3-----------

    FMT0 LO

    FMT1 HI

    OWLO LO

    OWL1 LO

    S/M LO

    /DIT LO

    DITCLK1 LO

    DITCLIK0 HI

    DITFMT LO

    DITMONO LO

    SW6------------

    X2 HI

    X1 LO

    EXTCLK HI

    JUMP 1 ON

    JUMP 2 ON

    JUMP 3 ON

    JUMP 4 ON

    JUMP 5 3&4

    JUMP 6 3&4

    All the best,

    Chris

  • 0 in reply to Chris Ash
    TI__Guru**** 174821 points

    Hi Chris,

    Can you double check your SW3 settings?  If DITFMT is LO, then both FMT0 and FMT1 should be LO.  Unfortunately I do not have hardware in from of me to verify this, but let me know what you find on your end.

  • 0 in reply to Tom Hendrick
    Prodigy 50 points

    Hi Tom,

    Sorry about that! That was a typo, I meant to type LO for all three. Running the unit in Left Justified data format. Went back through the user guide and didn't find any with the switches. Will check again tomorrow.

    I currently don't have it in a proper enclosure, just testing it, could the noise be from stray interference? It doesn't have any noise at 44.1khz without an enclosure, but not having an enclosure may be a contributing factor...

    Best,

    Chris

  • 0 in reply to Chris Ash
    TI__Guru**** 174821 points

    Hi Chris,

    OK - thanks for the added detail!  Let me dig into this a little more and see what I can find out for you.  I should have hardware to look at tomorrow but it might be early next week before I can give you an answer.

  • 0 in reply to Tom Hendrick
    TI__Mastermind 23050 points

    Hey Chris,

    Tom and I spoke about this and I should be able test this with hardware tomorrow. I don't see anything immediately wrong with your jumper configuration at least regarding the PCM4222. How are you analyzing the audio data? Are you using the onboard DITs or measuring directly at the audio serial interface header? Do you have a capture of what the output spectrum looks like that you could share? 96Khz operation does give a bandwidth of 48kHz, so it is possible that if you have any ultrasonic sensors in the area that you may be picking up some interference, but I tend to see these operate closer to 80kHz and above so I don't think this is very likely. You may also want to probe the clock lines to verify that your data format is correct and matches what your processor or measurement equipment is expecting. If there is any misalignment in the data this can dramatically shift the apparent noise floor.

    Best,

    Zak

  • 0 in reply to Zak Kaye
    Prodigy 50 points

    I'm hearing the noise in Logic Pro X. Using the SPDIF output. Here's a capture of the spectrum of the noise. The system is able to be clocked by the PCM4222, so I believe the data format is correct, just the digital audio signal is giving noise. Thanks for your help!

    Best,

    Chris

  • 0 in reply to Chris Ash
    TI__Mastermind 23050 points

    Hey Chris,

    I tested on an EVM in our lab with your same switch settings using the J7 AES-3 output and observed the following results:

    It's running at 96kHz and the noise floor is exactly where I would expect it to be. It seems there is nothing wrong with the EVM in this configuration unless somehow or another some of the parts on your EVM have been damaged.

    How are you interfacing this to Logic Pro X though? I'm assuming you have an XLR to USB audio interface device between the EVM and your PC? You may also want to verify that the device your are using can support 96kHz digital audio.

    Best,

    Zak

  • 0 in reply to Zak Kaye
    Prodigy 50 points
    Hi Zak,
    I'm using the SPDIF port on the EVM to communicate to a digidesign 002R. It's capable of 96khz. The interface is capable of being clocked by the EVM at 96khz and receiving and playing audio at 96khz. I'm using the analog inputs of the EVM, then using RCA 75ohm SPDIF cable to connect to the interface, and the interface is using firewire to connect to the laptop. The noise floor is at -53dBFS at the moment. I don't have the time or the resources to continue troubleshooting this at the moment, so I think until further notice, I will use the EVM as an external clock to clock both the interface and an external D to A converter I've been using to monitor. Seems to work. I hope nothing's damaged, but I can't spend time trying to troubleshoot it. Thanks for your help!
    Best,
    Chris