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My project log (two stereo XLR out, MIDI, DMX, SD-Card, Display, DRAM)

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  • My project log (two stereo XLR out, MIDI, DMX, SD-Card, Display, DRAM)

    Hey everyone!

    I enrolled to this excellent course as a way to put some pressure on myself to finish an age long project. This is its fifth redesign, and this time I will see it through!

    Layout has not begun yet. It felt weird to paste screenshots of the schematic so I attached it as a PDF.

    My TODO:
    • Double check net labels (will probably find some while routing)
    • Consolidate component values (DFM) and make sure all buttons has at least a series resitor
    • Clean up some of the TVS schematic so they are more intutive to read (XLR protection, I'm looking at you)
    • Re-annotate with refs having first digit reflect the schematic number (i.e R101, not R1)
    • Investigate SD detect pins, probably something missing there
    • Consider BUS for DRAM, kind of like the way it looks now though
    Any and all feedback very much welcome!

    EDIT: New version with PCM5102A (no I2C needed, yay) and replace XLR driver DRV135 with better part THAT1646. Thanks SauceBoss !
    Attached Files
    Last edited by AlexanderBrevig; 01-30-2022, 03:51 AM.

  • #2
    Whoa Man!

    That's a mature, advanced project if I ever saw one!

    A thing or two for you to consider:
    • Why have you chosen PCM5121? It's neither best equipped, nor best measuring DAC of this range? Are you going to use internal DSP? Why not use simpler PCM5102 (with better parameters), or PCM4104 (but it requires external analog stage and I understand you want to skip that)?
    • DRV135 are kind of obsolete when you can get THAT Corp parts: (you can't see that in this pdf, but they usually work much better in real life conditions)
    Overall it looks great and I can't wait to see it working!


    • #3
      I have a few PCM5121 and DRV135 on hand. But in such low quantity that I should reconsider. PCM5102A seems like a perfect part. Thanks! I will change to it!
      THAT16x6 also looks better, thanks! (It's even obtainable!)

      Thanks for the input, I will update tonight


      • #4
        Unfortunately the PDF is not searchable. So where do you use +3.3VA?


        • #5
          I don't know how much quality-oriented are you in this project AlexanderBrevig, but word on the street is that PCM5102 sounds much nicer when buffered with something, instead of going straight from it (despite what mfg says). If you feel like it, you can always drop in NE5532 as a voltage follower, or if you feel especially cheeky INA1622 with internet resistors for an extra small footprint and bonus coolness points.

          Always happy to help!


          • #6
            Hey qdrives! 3.3VA is currently only used for reading two potentiometers. (This schematic has a bug where they don't use 3.3VA.) I don't remember if the uploaded schematic still had a separate regulator for 3.3VA, that is no longer the case. Both my 3.3 rails are a ferrite bead away from an LDO.

            I will post a new schematic tomorrow
            Thanks SauceBoss, I guess you are referring to the jack outputs? They are only for testing this spin. There will not be any jacks on the final version, and signals are buffered by the XLR driver. Thanks again!