Noise from input jacks.

[BigBubbaBrown]

My current setup is a PreSonus Audiobox USB. It works great for MIDI, but I get noise whenever I use the line-in/XLR inputs. It doesn't matter what's plugged into it or how it's plugged in. When I set up a track for line-in in my DAW if anything at all is plugged in I get a bunch of rapid clicking. If I plug my keyboard directly into the line-in it does it, if I hook a microphone up via XLR it does it, running my keyboard to a direct box (Sidekick passive if that makes any difference) won't get rid of it no matter what position the ground lift switch is in, and if I just take the 1/8" to 3/4" converter jack off of my headphones and plug it in, nothing plugged into the converter, it's enough to get it to clicking. I've also tried an empty XLR cable (nothing attached to the other end), my mic in both the on and off position, and when my keyboard is plugged in, whether directly through line-in or via XLR through the direct box, it does it whether the keyboard is on or off.

 

I thought it might be electrical interference since it's sitting on my computer desk with my subwoofer on the shelf below it, my PC tower on the shelf below the subwoofer, my telephone sitting right in front of it (land line so I can't move it as easily as I could find a new place to store my cell phone), and my modem right above it so I got the longest USB cable I could find and moved it to the other side of the room. That didn't even diminish the problem, let alone get rid of it. I fiddled with the knobs on the front. By the time I got it low enough to where I couldn't hear the clicking I could barely hear my keyboard with the volume slider moved all the way to the top.

 

It's too loud to noise gate. I've even tried the bare minimum when no sound was coming from the keyboard, but the gate plug-in still interfered with the audio. Basically I've done all of the troubleshooting I can think of and it isn't any better. I'm new to the whole non-MIDI thing, other than running a toy keyboard into a cassette recorder as a kid, so I'm not even sure what else to look for.

[john]

It sounds like crosstalk. Obvious culprits are things like audio cable to audio cable, and more likely digital cable to audio cable or power supply to audio cable, but you also have to guard against crosstalk between power supplies due to power supply coupling and powersupply crosstalk.

 

Is the power supply to your computer and the Audiobox isolated and filtered? If the line in/XLR is routed too close to the power on the Audiobox circuitry you might get crosstalk from the power. So power supply crosstalk can occur. The same can be true of digital cables or midi cables spilling onto power supplies and then the powersupply either directly gets into the audio chain due to unfiltered supply to things like amplifiers or onto the audio chain by crosstalk onto the audio signal circuitry directly. Check the routing of the supply for your computer and audiobox. Keep power supply cables separate from analog audio, separate from digital audio, separate from midi cable. Digital audio and midi cables are notorious sources of clicking. ie keep all cables with similar types of cables.

 

Power supply coupling can be a real pain. It means  getting something that will isolate and condition your power supply:

 

https://www.studiospares.com/Cables-Leads/Mains-Distribution.htm?pl=2147483647

 

I use a unit similar to the Adam Hall PCL10.

 

Before you go buying that, put some real effort into isolating all your cables.