Harmonic Distortion in UMC404HD

  1. #1 by June Kim on 12-23-2017
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    Harmonic Distortion in UMC404HD

    Sine wave at 1kHz -20dbfs from an audio mixer is recorded into UMC404HD's 1 and 2 inputs via balanced cables. As you can see from the image in the following link, there seems to be a high amount of harmonic distortion. Compared to my other audio interfaces(like Scarlett 18i8), the harmonic distortion is much greater.

    https://imgur.com/a/dSU7M

    BTW, I couldn't find THD specification of UMC404HD from the internet.
  2. #2 by Ken Mitchell on 12-26-2017
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    - June Kim wrote View Post
    Sine wave at 1kHz -20dbfs from an audio mixer is recorded into UMC404HD's 1 and 2 inputs via balanced cables. As you can see from the image in the following link, there seems to be a high amount of harmonic distortion. Compared to my other audio interfaces(like Scarlett 18i8), the harmonic distortion is much greater.

    https://imgur.com/a/dSU7M

    BTW, I couldn't find THD specification of UMC404HD from the internet.
    Hi June,

    Welcome to the forums. I'm interested in your test setup so I can try to reproduce what you are seeing. It looks like you are running Reaper on Windows as your DAW and SPAN for spectrum analysis. What are you using to generate the test signal into the mixer and what mixer are you using to output to the UMC404HD?

    I noticed your test signal was mono so I pulled it into Reaper and rendered a stereo track. I then played that back using Audio Highjack Pro through the Aux outputs of a Behringer XR18 mixer into the UMC404HD. The XR18 and UMC404HD are connected using balanced XLR cables.

    Attached is the output I see from SPAN. I am getting a high frequency tilt but that appears to be there whether or not I have an input signal or not.

    Interested in exploring this more.

    Ken
    Attached Images Attached Images
  3. #3 by June Kim on 12-27-2017
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    Hi Ken,

    First of all, thank you for your interest.

    To generate the test signal into the mixer, I played the signal from foobar2000 player through an ASIO driver, or I also tried playing the signal through an ASIO driver, from another Reaper instance. The mixer is Yamaha MG10XU, which is connected to the PC via USB. I am using the stereo out of the mixer with balanced TRS cables.

    I saw your output and it was surprisingly clean compared to mine. At first I was at a loss. However, I figured out a suspicious difference between you and me. You used a pair of XLR cables whereas I used a pair of TRS cables. So I experimented with a pair of XLR cables from the stereo out of the mixer(there are two XLR outs and two TRS outs, electrically parallel to each other).

    Now I see clean signals just like you. I'd like to see what happens when you use TRS plugs into UMC404HD.

    June
    - Ken Mitchell wrote View Post
    Hi June,

    Welcome to the forums. I'm interested in your test setup so I can try to reproduce what you are seeing. It looks like you are running Reaper on Windows as your DAW and SPAN for spectrum analysis. What are you using to generate the test signal into the mixer and what mixer are you using to output to the UMC404HD?

    I noticed your test signal was mono so I pulled it into Reaper and rendered a stereo track. I then played that back using Audio Highjack Pro through the Aux outputs of a Behringer XR18 mixer into the UMC404HD. The XR18 and UMC404HD are connected using balanced XLR cables.

    Attached is the output I see from SPAN. I am getting a high frequency tilt but that appears to be there whether or not I have an input signal or not.

    Interested in exploring this more.

    Ken
  4. #4 by Ken Mitchell on 12-27-2017
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    Posts: 1,128
    - June Kim wrote View Post
    Hi Ken,

    First of all, thank you for your interest.

    To generate the test signal into the mixer, I played the signal from foobar2000 player through an ASIO driver, or I also tried playing the signal through an ASIO driver, from another Reaper instance. The mixer is Yamaha MG10XU, which is connected to the PC via USB. I am using the stereo out of the mixer with balanced TRS cables.

    I saw your output and it was surprisingly clean compared to mine. At first I was at a loss. However, I figured out a suspicious difference between you and me. You used a pair of XLR cables whereas I used a pair of TRS cables. So I experimented with a pair of XLR cables from the stereo out of the mixer(there are two XLR outs and two TRS outs, electrically parallel to each other).

    Now I see clean signals just like you. I'd like to see what happens when you use TRS plugs into UMC404HD.

    June
    HI June,

    While I would not have thought there would be a difference between XLR and TRS that appears to be the difference. Unfortunately the XR18 only has XLR outputs so I couldn't just swap in TRS cables. Instead, I had to feed the XR18 output into an old Xenyx Q802 I had in a cabinet and then take the TRS outputs of the Q802 into the 404HD.

    Look what I found. It appears you have found a design flaw (or at least a weakness).

    Ken
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  5. #5 by June Kim on 3 Weeks Ago
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    One Month Later

    So it's been a month. I've contacted the customer service. We exchanged email several times but it seemed like no progress at all.

    They insisted:

    1) THD(Total Harmonic Distortion) of UMC404HD is proprietary information and they didn't share it.
    2) I have to gain stage properly
    3) If there is no audible noise, then UMC404HD is working to its specification
    4) If I hear audible noise, I should try noise gate
    5) If it's within 30 days of purchase, return it

    This is very disappointing. I doubt they actually read my initial report with care.

    Harmonic distortion cannot be handled with a noise gate, since it's distortion happening at the same time with the signal. At least two independent experiments(me and Ken here) showed the flaw at the TRS jack of UMC404HD but they don't seem to have investigated it enough.

    Last edited by June Kim; 3 Weeks Ago at 09:18 AM.
  6. #6 by Ken Mitchell on 3 Weeks Ago
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    - June Kim wrote View Post
    So it's been a month. I've contacted the customer service. We exchanged email several times but it seemed like no progress at all.

    They insisted:

    1) THD(Total Harmonic Distortion) of UMC404HD is proprietary information and they didn't share it.
    2) I have to gain stage properly
    3) If there is no audible noise, then UMC404HD is working to its specification
    4) If I hear audible noise, I should try noise gate
    5) If it's within 30 days of purchase, return it

    This is very disappointing. I doubt they actually read my initial report with care.

    Harmonic distortion cannot be handled with a noise gate, since it's distortion happening at the same time with the signal. At least two independent experiments(me and Ken here) showed the flaw at the TRS jack of UMC404HD but they don't seem to have investigated it enough.
    Hi June,

    While I agree the responsible is rather disappointing I can't say that I'm surprised. If it isn't a driver, connectivity, or configuration issue most tech support folks won't be able to solve it. I'd recommend sending a PM to Michael Lapke asking him to have a look at this thread. Be patient. With NAMM later this week it may take him a while to respond.

    Ken

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  7. #7 by Michael Lapke on 3 Weeks Ago
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    Hey June,

    My apologies for not replying to this thread earlier. Honestly I'm not sure why you would be seeing this with TRS vs XLR cable, unless there was an issue with the TRS cables in question. What exactly does the Yamaha Mixer add to the equation? Is there a specific reason why you need to use it with your UMC404HD? Further is there a reason why you're using ASIO drivers instead of the recommended proprietary ones we provide here on our website?

    You could always eliminate the Mixer and try using the UMC drivers to see if it still happens. Beyond that or any of the suggestions CARE provided I'm really not sure what else to recommend for you. Please keep me posted if you are able to make any progress.

    Michael Lapke
    Specialist, Community
    MUSIC Tribe
    BEHRINGER
  8. #8 by Ken Mitchell on 3 Weeks Ago
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    - Michael Lapke wrote View Post
    Hey June,

    My apologies for not replying to this thread earlier. Honestly I'm not sure why you would be seeing this with TRS vs XLR cable, unless there was an issue with the TRS cables in question. What exactly does the Yamaha Mixer add to the equation? Is there a specific reason why you need to use it with your UMC404HD? Further is there a reason why you're using ASIO drivers instead of the recommended proprietary ones we provide here on our website?

    You could always eliminate the Mixer and try using the UMC drivers to see if it still happens. Beyond that or any of the suggestions CARE provided I'm really not sure what else to recommend for you. Please keep me posted if you are able to make any progress.
    Hi Michael,

    Please take a look at my post here: https://forum.musictri.be/showthread...l=1#post137627

    I can reproduce the same result using a digital signal generator through the AUX outs of an XR18 via USB. Obviously, my XLR-to-TRS cables aren't the same ones June is using and the harmonics are not there in the exact same configuration when XLR-to-XLR cables are used. Also, I'm on a Mac so no ASIO nor proprietary drivers involved.

    Ken

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    If you want "Loud", then run a piece of sheet metal through a table saw. --Ivan Beaver
  9. #9 by Michael Lapke on 3 Weeks Ago
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    - Ken Mitchell wrote View Post
    Hi Michael,

    Please take a look at my post here: https://forum.musictri.be/showthread...l=1#post137627

    I can reproduce the same result using a digital signal generator through the AUX outs of an XR18 via USB. Obviously, my XLR-to-TRS cables aren't the same ones June is using and the harmonics are not there in the exact same configuration when XLR-to-XLR cables are used. Also, I'm on a Mac so no ASIO nor proprietary drivers involved.

    Ken
    Hi Ken,

    I did indeed take a look at the entire thread, including the post you linked just now.

    With my reply I was trying to eliminate any mixers from the equation to see if the end result is still able to be reproduced. We need to find out if it's possible to plug in a signal generator directly to the UMC404HD, using the drivers we provide for this product (if necessary), and if we can still see these harmonics. There may be other factors at play here, and this is what I hope to determine after hearing June's reply.

    Michael Lapke
    Specialist, Community
    MUSIC Tribe
    BEHRINGER
  10. #10 by Ken Mitchell on 3 Weeks Ago
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    Posts: 1,128
    - Michael Lapke wrote View Post
    Hi Ken,

    I did indeed take a look at the entire thread, including the post you linked just now.

    With my reply I was trying to eliminate any mixers from the equation to see if the end result is still able to be reproduced. We need to find out if it's possible to plug in a signal generator directly to the UMC404HD, using the drivers we provide for this product (if necessary), and if we can still see these harmonics. There may be other factors at play here, and this is what I hope to determine after hearing June's reply.
    Thanks Michael.

    Just wanted to make sure you understood that is wasn't just occurring in June's setup. Here are a couple measurements of an external signal using TRS and XLR inputs on channel 1. The only difference between the two measurements is the XLR measurement is with the TRS plugged into a Hosa GXJ-235. I suspect the high frequency noise on the XLR measurement is due to the coupler. I've seen that before with other measurements and it's even present without the signal generator on.

    One other thing I noticed was common between June and I was that we were both using SPAN for making the measurements so I switched to using Oscarizer instead just to confirm it wasn't something to do with SPAN.

    Again, I'm on a Mac so no drivers beyond CoreAudio.

    Ken
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    -------------------------------------------------------------------
    If you want "Loud", then run a piece of sheet metal through a table saw. --Ivan Beaver