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Thread: SGTL5000 compared to PT8211

  1. #1

    SGTL5000 compared to PT8211

    Hi!

    I used for my project (MicroDexed) a Teensy-Audio-Board (SGTL5000) and it sounds really good (and works for 16 voices with only 2 Blocks of audio memory). But when using the same code (adapted for the PT8211, using the Teensy-Audio-Design-Tool) it seems that I am getting much memory problems. AudioMemoryUsageMax() reports something about 50.000 (!!!). I have seen that four-times-oversampling uses much memory, so I turned it of for a test. But there were also drop outs due to memory problems.

    Does the PT8211 "driver" really needs much more memory than the SGTL5000 - or do I have a problem in my code?

    Thanks and Regards, Holger

  2. #2
    Senior Member+ Theremingenieur's Avatar
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    Without looking deeper into the audio library’s source code, I’d guess that a simple PT8211 output without oversampling should not be that memory consuming and I’d look for the problem elsewhere.
    The oversampling itself, when it is done with a lengthy zero phase FIR, might be extremely resource consuming. I made some tests, just generating a 48ks/s sine wave in real time with a high Q SVF, followed by x8 oversampling on a Teensy 3.2 without audio library, some years ago, and that was enough to saturate the poor little Teensy.

    Besides of that, new designs based on the obsolete PT8211 are not recommended.

  3. #3
    Quote Originally Posted by Theremingenieur View Post
    Without looking deeper into the audio library’s source code, I’d guess that a simple PT8211 output without oversampling should not be that memory consuming and I’d look for the problem elsewhere.
    The oversampling itself, when it is done with a lengthy zero phase FIR, might be extremely resource consuming. I made some tests, just generating a 48ks/s sine wave in real time with a high Q SVF, followed by x8 oversampling on a Teensy 3.2 without audio library, some years ago, and that was enough to saturate the poor little Teensy.
    Ok, thanks for this information. I have an idea where the memory problems may come from.

    Quote Originally Posted by Theremingenieur View Post
    Besides of that, new designs based on the obsolete PT8211 are not recommended.
    Sure, but the PT8211 is currently the easiest and cheapest way to get something like sound out of the Teensy via I2S. The TSOP housing is the only way for me to get an I2S interface soldered on a PCB :-(

    Regards, Holger

  4. #4
    Senior Member+ Theremingenieur's Avatar
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    I'm currently experimenting with a cheap (3.14€) chinese PCM5102A breakout module. The PCM5102A has integrated x8 oversampling which makes things much easier.

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    Quote Originally Posted by Theremingenieur View Post
    I'm currently experimenting with a cheap (3.14) chinese PCM5102A breakout module. The PCM5102A has integrated x8 oversampling which makes things much easier.
    I successfully used the PCM5102A and it sounds much better than the Audio Shield.
    https://forum.pjrc.com/threads/53069...Module-via-I2S

    Ultimately, though I wish to use the PCM5242. This would give me entry level audiophile quality sound. I just bought the evaluation module and I'll be hooking it up. I'm not a coder though, so I suspect I'll struggle "writing" the firmware to initialize the chip. I'll try...

    My goal will be to run the PCM5242 DAC in TDM mode with a Teensy. I'll be looking to hire a good firmware developer to help me along. If anyone is interested in paid work to do this let me know.

  6. #6
    Senior Member+ Frank B's Avatar
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    The pt8211 code does not use that much memory. It does not use more than the SGTL code.
    Can you please post an example?
    I wrote parts of the code and would like to fix the bug- if there is any. But I need something that helps me to reproduce the problem.
    This is the first time I hear about it, and it is unlikely that it has a memory problem.

    Also, please give examplecode for dropouts.
    Last edited by Frank B; Yesterday at 08:27 AM.

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