Raspberry Pi I2S to SPDIF Hat

Discussion in 'Digital: DACs, USB converters, decrapifiers' started by Michael Kelly, Apr 30, 2016.

  1. bilboda

    bilboda Florida boomer

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    Strange, I could edit older an post of mine in this thread....I am looking at one from 12/31/2016 and it has an edit button...
     
  2. Em84

    Em84 New

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    Hi @Michael Kelly

    Is your upcoming AKM based DAC HAT planned to support DSD processing? Or only PCM?

    Cheers
     
  3. jcn3

    jcn3 New

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    so can you get sound out of any of the digital outputs or the analog rca line out? i'd check those -- if you can get sound there at least you know the dac is working.
     
  4. Michael Kelly

    Michael Kelly MOT: Pi 2 Design

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    The headphone out was removed and is not supported. So nothing will come out. Only the digital and the RCA jacks are supported. It sounds like you have a very early beta unit?

    Cheers,
    Michael
     
  5. Michael Kelly

    Michael Kelly MOT: Pi 2 Design

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    Only PCM. But the 502DAC2 is being delayed. We are proceeding with the 502DAC3 but with the high end PCM1792. Test results as of today are very, very good. I will be posting an update on this as well as the acrylic cases tomorrow.

    Cheers,
    Michael
     
  6. Clemmaster

    Clemmaster Friend

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    @Michael Kelly , is there a replacement campaign for the boards with headphone output?
     
  7. Michael Kelly

    Michael Kelly MOT: Pi 2 Design

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    You have a beta unit? I think I mentioned before that we will replace all beta units free of charge. Just send me an email at [email protected]

    Cheers,
    Michael
     
  8. Martin_W

    Martin_W New

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    Someone pointed that out to me already thanks and I've got it working. Its great.

    thanks to all who helped me out and to Michael for a great card.
     
  9. Michael Kelly

    Michael Kelly MOT: Pi 2 Design

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    Sorry for the silence! Always too much to do and not enough time. Following are some updates on the new 502DAC2 (AK4490EQ) and DAC3 (PCM1792) as well as the cases for them and the 502DAC.

    502DAC Case - design complete and we have them in stock. Just waiting on the screws which will be here Monday, we can start shipping Tuesday (need some time to make up the kits). Initially the case will be free of charge, shipping only. Eventually it will be $10 + shipping. I don't have the shipping cost yet as I am waiting for the final weight. Best guess is around $5 for US and $10-12 for international. Value for VAT and taxes will be $5 so hopefully no pain there! It will be in the store by Tuesday with the shipping info.

    502DAC2 (AK4490EQ) - Yours truly (that's me BTW) messed up the design and it needs a re-spin. Based on the great testing results of the 502DAC3 (PCM1792) we may pull the plug anyway.

    502DAC3 (PCM1792) - As mentioned this board is working flawlessly and giving fantastic results. In the category of $400-$1,000 DAC/Amps. I have the following test results I can share, but not sure the best way. Posted here or on our web with a link here.

    DAC Output
    1. 1Khz THD @ 0db
    2. 1Khz THD @ -5db
    3. 1Khz THD @ -60db
    4. Noise @ 0 output
    5. 44.1Khz, 16-Bit Jitter Test
    6. 48Khz, 24-bit Jitter Test
    7. 96Khz, 24-bit Jitter Test
    8. Noise at 0 output
    LME49600 HP Out
    1. 1Khz THD @ 0db into 100K ohm
    2. 1Khz THD @ 0db into 32 ohm Headphone (AKG K7XX)
    3. 1Khz THD @ 6db into 32 ohm Headphone (AKG K7XX)
    4. 1Khz THD @ 12db into 32 ohm Headphone (AKG K7XX)
    5. Noise @ 0 output
    Let me know how you guys want the data. Note that I also have the DAC out results for the 502DAC. Pretty good for a basic DAC.

    Cheers,
    Michael
     
  10. hifiandrun

    hifiandrun Almost "Made"

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    Hi Michael,

    Wonderful ! I would like to have one of your new DAC3 with the HP out. Please add me on your list!

    Is the output layout similar to the 1st 502DAC? It would be great if I could use the aluminum case I made for the 502DAC.

    Cheers,
    Rong
     
  11. Michael Kelly

    Michael Kelly MOT: Pi 2 Design

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    We plan to have a crowdfunding campaign for the original 502DAC as well as the new one with the TI part. But we will have a small number of them available well before the campaign ends. We will offer those to the super best audio list and we will announce that when it is ready.

    The layout is very similar. The end with the digital connectors and LED stayed the same, the side where the audio jacks come out has the headphone jack where the two wire connector was. That has now moved to the end with the DC Jack. If you want I can send you a step file to review.

    I will also take some pictures and post them tomorrow or Saturday, when I get back into the office next.

    Cheers,
    Michael
     
  12. Clemmaster

    Clemmaster Friend

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    Always in for some data!
     
  13. Scott Kramer

    Scott Kramer Friend

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    How'd you pull off master mode with the PCM1792, using the WM8804 and digi+pro driver? Also no built in op amps (a la the PCM51xx)... are you doing an output stage?
     
  14. Michael Kelly

    Michael Kelly MOT: Pi 2 Design

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    If you look at the PCM1792 data sheet you will see the recommended output circuit which we have followed. We have also implemented the LME49600 circuit for the headphone. We use high efficiency switchers with low noise LDO followers for the +/- 10V supply. That coupled with the high PSRR of the LME49720 opamps gives us a noise floor of around -130db.

    The PCM1792 is wired for HW mode so the WM8804 driver handles the clocks and I2S interface.

    Cheers,
    Michael
     
  15. Xen

    Xen Friend

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    First, where am I coming from… I picked up the 502DAC for many reasons.

    1) Move my music off a RAID10 on a big linux server to a Raspberry Pi-based solution. The RPi will be using a clone of the music folder with the master files on the RAID10.

    2) Play with BNC transport to Gungnir Multibit.

    3) Build an LPS for the new RPi+502DAC or “How I learned what the Raspberry Pi wants and what the 502DAC gives”. This is very long.

    I’m the only person that will probably care about #1. I need to write up my experience with MoOde over on the RPi as Transport thread.

    Part 2

    I’ve let my brain become accustomed to the sound of the 502DAC and switching between USB (Linux, DeadBeef, exlusive mode ALSA), TOSLINK (Win10, foobar2000, WSAPI push), and BNC (RPi3 rev2+502DAC rev3, mpd+MoOde, exclusive mode ALSA), the music is seamless. Everything goes into Gungnir Multibit, and I can just hit the source cycle button to listen to whichever transport I choose. There is definitely no “Night and Day” difference between any of the connector-types. My brain is unable to detect much variation (loss or gain). I can pretty much instantly tell the difference between my Black Widow 2 (SE) vs Liquid Carbon (SE or BAL, more easily through BAL) due to some noise (and maybe distortion from the BW2) on the SE inputs.

    I really like the versatility of the 502DAC. To get music off the RPi, you have a choice of Analog RCA, BNC/RCA digital, TOSLINK digital, TRS/AES digital, and even I2S if you are Scott Kramer crazy (I applaud your skillz, man! No sarcasm.). As a digital transport, it only adds about 0.5W of energy dissipation to your system.

    Michael Kelly has been just great with customer service, listening to our feedback, and implementing that feedback into the product. This quality of service deserves my hard-earned dollars!

    Part 3

    #3 is a weird one. In a previous post, I wrote that my Rev3 board was unable to power my RPi3r2. Michael was extremely generous and took back my Rev3 board and sent me a Rev4 board, which I got today. I hooked it up and found … it ALSO couldn’t power the RPi3r2. So now, I am thinking my RPi3r2 board is damaged and my thoughts to create a single LPS now doubled as I would have to power each board separately.

    I hope this information will help anyone else wanting to build an LPS for a similar setup. Today has been a learning experience…

    I have been learning how to use an oscilloscope, so I thought I would scope out what was happening to the voltage coming from the 502DAC. I hooked up Pin2 (5V) and Pin6(GND) between the RPi and 502DAC. I probed at the power supply, between Pin4 (5V) and Pin14(GND) on the 502DAC, and between Pin2 and Pin20(GND) on the RPi3.

    I found that the voltage supply from the bench power supply was rock steady. There was a substantial voltage drop between the PSU and output pins on the 502DAC, about 0.4 to 0.6 V. Maybe due to my setup (using breadboard wired pins) there was another drop at the RPi3 side of about 0.2V. However, the RPi3 voltage was not stable! It would bounce, down another 0.2V randomly. So, 5.2V in, 4.7V out, and <4.5V at the RPi3. My RPi3 wants >5.00 V at ALL TIMES. Any dip below 5.0V and the red PWR light goes out and the CPU freezes.

    So, I tested various input voltages and measured when the voltage at the RPi3 would be >5.0V. I was more afraid of the tolerance of the RPi3 since the 502DAC uses an LT3042 which can handle 20 V input. On my setup, I found that close to 6 V on the input would be 5.4 V at the RPi3 side. When the RPi3 is chugging, there are brief periods where the voltage drops below 5.0 V, but the RPi3 seems to be able to handle it.
    NewFile1.png NewFile3.png NewFile4.png
    EDIT: Sorry, forgot to label the lines. Yellow is straight off the bench Power Supply. Blue at the GPIO on the 502DAC side. Purple is the GPIO on the RPi3.

    The “official” SMPS wall wart seems to deliver a pretty constant voltage. Scoping across Pin2 and Pin14 again, the voltage varies about 5.15 to 5.25 V and lower ripple than from my HP 6253A…

    So, is there an issue? Is the issue in regulation of the LT3042? Neither power supply was current limited. This affects both of my bench PSU’s, even though I only scoped off the HP. I was powering the Hat with my other PSU.
     
    Last edited: Jul 27, 2017
  16. Michael Kelly

    Michael Kelly MOT: Pi 2 Design

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    Have you run the pi and 502DAC from the pi supply alone?

    Cheers,
    Michael
     
  17. Michael Kelly

    Michael Kelly MOT: Pi 2 Design

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    Also what kind of USB devices do you have attached?

    Cheers,
    Michael
     
  18. Xen

    Xen Friend

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    Sorry, that was buried in my gigantic post. The voltage from the SMPS as the only source was fairly stable, between about 5.12 to about 5.25 V

    When I had the rev3 board, everything (Pi, Hat, USB Drive, Ethernet, BNC) ran fine from the SMPS wall wart. No idea what it looked like as I just recently got the oscilloscope.

    None. I scoped it on my workbench with only the Pi and the Hat. MoOde does activate hardware on the Pi like WiFi and BlueTooth. Nothing else was physically attached to either board. Power was supplied only through the DC barrel jack on the hat or only through the microUSB on the Pi. W1 was shorted at all times.
     
  19. Michael Kelly

    Michael Kelly MOT: Pi 2 Design

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    Try removing the jumper and power seperately. I am not sure what's going on, but it is very odd behavior.

    Cheers,
    Michael
     
  20. Xen

    Xen Friend

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    It's very possible that I have a funny Raspberry Pi3 as that is the only constant left. Maybe the part that handles power from the GPIO pins is messed up...
    I need to try powering the Pi through the GPIO pins without the hat.

    EDIT: The Raspberry Pi, without the hat, seems to work fine when powered through Pin2 and Pin6 directly by the bench PSU.
     
    Last edited: Jul 27, 2017

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