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Original question:

PCM2912A: Ticking / clicking sound constantly on mic and speaker

PCM2912A: Ticking sound on headphone output and microphone input

Matt Crane
Prodigy 20 points
Part Number: PCM2912A

Tool/software:

I found this forum post from a while ago, where this user had a very similar problem that I am having with the PCM2912A:

https://e2e.ti.com/support/audio-group/audio/f/audio-forum/752376/pcm2912a-ticking-clicking-sound-constantly-on-mic-and-speaker


The audio playback and microphone recordings sound clear and fine, except that during audio playback there is a ~300BPM rapid ticking sound, and during microphone recordings there is a repeating audio buzz, about every 0.8 seconds.

My schematic for reference, I believe is 1 to 1 with the recommended schematic in the datasheet, though I have added a headphone detection circuit to it:

I've attached an MP3 file showing the sound oddities.

The first 8 seconds is the chip recording a 300Hz sine wave via a headset microphone (I held a speaker up to the mic that was playing the tone). You can hear a sharp buzz every 0.8 seconds or so.

The next 8 seconds is recording the audio output of the chip into my audio interface. Same 300Hz sine wave being played, and you can hear there is a ~320BPM ticking sound.

For reference I've tried using the board with my computer, changing the sample rate and bit depth had no effect. The final application for this board will be using it with a USB-C iPad, and I have the same problem when connecting it to an iPad.

Anyone have an idea for what the problem could be?

Thanks,

Matt

  • 0
    TI__Mastermind 33660 points

    Hi Matt,

    I've seen something similar happen when mic circuits are incorrect for some reason. Do you have a way to play a signal directly onto the input, isolated from the jack? Also are you sure the headset you are using has the microphone on the sleeve connector? Many headsets have the microphone on the second ring (ground in your schematic). 

    Your schematic looks to be nearly exactly like the application diagram. The only differences are your resonator has the decoupling caps built into it? Do you notice any distortions in the clock coming from the crystal?

    I've not seen this problem before and have not run into it when I'm using an EVM. Would a EVM sample be helpful for you if the suggestions above don't work? That way you can have a working layout and see if the issue is on the host side or hardware side.

    Thanks,
    Jeff McPherson

  • 0 in reply to Jeff McPherson
    Prodigy 20 points

    Hey Jeff,

    I can try soldering a wire to the mic input and connecting it to an audio source.

    I am pretty sure that my headset has the mic on the sleeve connector, any idea as to how I could confirm that though? Oscilloscope on the pins maybe?

    Something to note is that I hear the rapid audio clicking even when I am using headphones that have a TRS connection, i.e. no mic and sleeve+ring2 are both GND.

    I can try looking at the clock signal on my oscilloscope as well, see what it looks like.

    A working EVM sample would probably be helpful to compare against!

    Thanks,
    Matt

  • 0 in reply to Matt Crane
    TI__Mastermind 33660 points

    Hi Matt,

    Sure. I've sent you a connection request here on e2e so you can give me a good shipping address privately.

    Thanks,
    Jeff McPherson

  • 0 in reply to Jeff McPherson
    Prodigy 20 points

    Thanks Jeff! I'll send that right away.