Noise in sound cards. Should I expect that?

J

johanmattsson

New member
Hi. I previously asked a question about noise in this forum and got many interesting answers but I am still no wiser. Here is what happened.

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I have an USB connected Editor UA-25 sound card and I can hear a warm humming noise in my loudspeakers when I have the HDMI cable connected. I tried different speakers, different computers and different screens, different output ports, same thing. I could only hear the unwanted sound when a screen was connected to the HDMI port. The amplitude of the noise did not change when I turned up or down the output volume on the card but I could make the noise less apparent by turning up the output volume on the card and turning down the volume on the monitor controller.

I bought a new USB sound card, Scarlet 2i2. No warm humming noise but a high pitched sharp tone was audible when the volume out from the sound card was low and the volume on the speakers was high. Similarly to the other card; the volume of the noise did not change when I turned up or down the volume. I tested this on different computers with different loudspeakers.

I find all this very strange and I can’t think of any likely cause to the problem. Please let me know if you have a theory.

Is this a common problem with sound cards? Should I just live with it and keep the output volume high enough and the speaker volume low enough so that the unwanted sound isn’t audible?
 
This shouldn't be happening but it is probably down to the grounding arrangement in your studio. Before going any further you need to give us a full list of everything in your setup (makes and model numbers) and the exact cable wiring between everything. Otherwise we're just guessing. Have you checked that your power sockets are properly grounded?
 
As James has said, you almost certainly have a ground, aka earth/hum loop. The fact that changing one of the components changed the NATURE of the noise but still kept the noise is a classical GL situation!

So, do as asked and give us chapter and verse. Also, can you solder?

Dave.
 
In fairness - it's rarely the external devices, but the computer. There is a big difference between a 50Hz main hum from an earth loop compared to the strange data bus noise - a sort of evolving and changing, harmonically rich noise. I'd bet this is what you have - sort of a frizzy, changing fuzziness - that often changes when you move the mouse, or in my office computer's case, it changes as the monitor picture changes. I have a slideshow always running on the desktop, and the noise changes 'quality' when the image shifts.

HDMI cables seem to distribute the noise, carried on the ground, around the studio. External devices that use the computer to power them seem the worst. The 5V and ground have this digital mush superimposed on it. Sometimes winding cables - HDMI, DC power, audio cables etc - through a big ferrite ring (like old loudspeaker magnets) half a dozen times, then taping - can make a difference if it's bad. Computers tend to be metal boxes and inside, no screening at all - so all that data running around to and from the drives 'leaks' into the grounds and gets spread around outside. The grounding info above is very typical for curing/reducing the 50Hz hums, but rarely does anything if your noise is digital in source. The sound is a 100% giveaway. We can spot a ground loop from digital noise very easily if you can find a way to record some?
 
"HDMI" cable? I assume you mean from computer to monitor screen, as neither audio interface you mention have HDMI! Does the noise go away when you disconnect the HDMI cable?
As both interfaces are USB powered, the fault is likely coming from somewhere in the computer part of your set up.
 
Is the 2i2 usb powered? My 18i8 is powered from mains.
Should the interfaces be sitting on top of a speaker containing powerful magnets?
 
Definitely isolate the studio monitors from other electronics. I also keep my cell phone away from the interface and computer.
 
Slouching Raymond said:
Is the 2i2 usb powered? My 18i8 is powered from mains.
Should the interfaces be sitting on top of a speaker containing powerful magnets?
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It shouldn't matter whether it is on top of the monitors - a properly designed interface won't be sensitive to permanent magnets like those in monitors. I think that the 2i2 is bus powered so it is somewhat dependent on the quality of the computer's power supply and grounding.
 
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