UMC404HD Output Problem

  1. #1 by David Sykes on 09-19-2018
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    UMC404HD Output Problem

    I've had an identical problem with two UMC404HD's and I am pretty sure it's an issue with the interface rather than my system. I'm running Logic Pro X and all 4 input channels from the UMC work fine. The problem I'm having is that the speaker outputs work for about 15-20 seconds then crackle and disappear completely. Exactly the same thing happens if I use headphones. I can work around it by switching the output to my Mackie mixer desk and then the speakers and headphones work perfectly. It's very weird that I've had this problem with both UMC's so I'm wondering if anyone else has had the same issue and if they were able to sort it out? My first unit was returned to the dealer for a full refund as they were out of stock and my second unit is just about to be exchanged by the dealer but I'm obviously concerned that the same thing might happen again. Any help would be appreciated. Thanks.
  2. #2 by Ken Mitchell on 09-19-2018
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    - David Sykes wrote View Post
    I've had an identical problem with two UMC404HD's and I am pretty sure it's an issue with the interface rather than my system. I'm running Logic Pro X and all 4 input channels from the UMC work fine. The problem I'm having is that the speaker outputs work for about 15-20 seconds then crackle and disappear completely. Exactly the same thing happens if I use headphones. I can work around it by switching the output to my Mackie mixer desk and then the speakers and headphones work perfectly. It's very weird that I've had this problem with both UMC's so I'm wondering if anyone else has had the same issue and if they were able to sort it out? My first unit was returned to the dealer for a full refund as they were out of stock and my second unit is just about to be exchanged by the dealer but I'm obviously concerned that the same thing might happen again. Any help would be appreciated. Thanks.
    Hi David,

    Welcome to the forums. My first thought is this is a buffering issue but I've seldom heard of the audio stopping completely. I'd recommend comparing the buffer settings in Logic between the 404HD and Mackie to see if there's a difference. Also, try increasing the output buffer for the 404HD to something really big just as a test.

    Hope this helps,
    Ken

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  3. #3 by David Sykes on 09-20-2018
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    Thanks Ken, I'll take a look at that but it seems unlikely that there's a buffering issue as my PreSonus interface works perfectly.... I only bought the UMC404HD for the convenience of 4 simultaneous inputs rather than the 2 on my PreSonus and I haven't changed any of the settings other than specifying the output. It's puzzling to say the least!
  4. #4 by Mark Farrell on 09-20-2018
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    Hi David,

    A little more information please......

    - What are you using for monitors/speakers and are you using balanced (XLR/TRS) or unbalanced (TS) cables for the connections?
    - Does it occur on both recording and playback while monitoring with just the headphones? (monitors disconnected altogether from the interface)
    - When the problem occurs is there gear connected to the interface inputs and what sort of gear is it.
    - Are you using the wall wart adapter to power the interface?

    Different problem, but kinda similar....... (explanation may be over your head )
    A few years back I had a Behringer mixer doing something similar with its inputs which were direct coupled and 'electronically balanced'. I would connect a particular piece of gear (can't remember what it was right at the moment) to the line input of the mixer and it would work fine for about 10-15 secs and then audio would fade out to nothing. Somehow the gear I was connecting to the mixer input had impressed a slight DC voltage on the cable along with the audio signal. This DC voltage altered the bias on the direct coupled input OpAmp which resulted in swinging the output of the OpAmp to an extreme that wouldn't output the audio signal. The 10-15 secs it took to occur was due to the time it took for a capacitor in the circuit to charge up delaying the change in the operating point bias.
    This took me some time to figure out. I think you may have a different problem, but rings of similarities to the problem I had.
  5. #5 by David Sykes on 09-20-2018
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    Thanks Mark, I appreciate your help.

    I'm using Alesis M1 Mk2 Active monitors and I'm connected with XLR at the interface and balanced jack at the monitors (and it works OK with my PreSonus interface). I haven't tried disconnecting the monitors and trying headphones only but I will try that tomorrow and get back to you. The inputs have at times had a Shure SM58 DI'd from a PA, a DI from a guitar amp and a DI from a bass amp connected - all using XLR's. Sometimes this gear has been switched off, sometimes it's been switched on.

    That problem you had sounds very similar so maybe I should unplug everything from the inputs and see what happens then? It's just possible that there's some problem with one of the 3 DI connections.

    Thanks again for stepping in.

    Regards,
    David
  6. #6 by Mark Farrell on 09-20-2018
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    Disconnecting gear one by one is a good way to troubleshoot a problem. Maybe with some luck you'll find something!!