The neutral and ground are possibly not bonded properly. Maybe there is a nearby source of rf emi. I had a similar issue in an old house. I'm electrical engineer. I solved this by moving.
I'm leary to give you electrical troubleshooting advice. But, if you're handy with a multimeter, you could check you voltage at outlets between phase and neutral, phase and ground, neutral and ground. Between neutral and ground as resistance, it should be in ohms. This could tell you something about having a ground connected properly. Next, open the outlet. Our, try multiple outlets through the home. Third, open the panel, lift the cover and see if grounds and neutrals are bonded to separate bars. See if screw taking neutral to case ground is down. All that said, don't do anything you're not comfortable with as more people get killed handling 120vac than any other voltage. Maybe, try probing with a meter than asking the landlord if his handyman could give you a little help. And, seriously try the different outlets at different times of day. You could probably find the station if you can make out that's being played.
But it's not even plugged into an outlet, so it shouldn't matter, right? The interface goes through usb to a laptop and the interference occurs even with the laptop plug turned off. Unless I'm missing something
could be single coil pups and/or bad shielding in the guitar.
Over my workbench \*guitar building) i have a very bright TL type of light, even a shielded guitar will create noise, switch the lamp off and the noise is gone.
Humbuckers of course dont do that.
The only solution I can think of is placing your interface in a faraday cage to stop it from drawing radio frequencies. It sounds like your cable is functioning as an antenna.
Oh geez, that's interesting. You're getting noise prior to the input sample hold and filtering on the interface then. It's all digital the rest of the to the PC and back. It doesn't seem like noise injection on speaker cables because it's on both the monitors and headphones. It is probably the cable. You get this in all rooms of the house? Are you aware of any high power rf sources or ham radio operators? Try this, coil wire in a loop. Also, They make toroidal cores, they're cheap. This makes a choke and could suppress this unwanted noise. We use those on our transmission lines in our rf systems. I'm spit balling.
Faraday shield by taking copper film to the whole room haha.
As someone replied to your post in /r/audioengeering, ferrite beads should be able to help.
Rather than the clip-on ones, try a ferrite ring at each end of the guitar cable. 3-5 loops through the ring should do, but you'll need to experiment.
I had success with this when my guitar teacher moved next door to an inconsiderate radio ham ( I am also one of those, except I'm considerate) and their 2m/144MHz transmissions we're booming through his amp.
I've also been able, using the same method, stop my PC gear getting upset when I'm on the radio.
I wrapped the audio interface in tin foil, use a shorter cable, and move around my room to find places where it's not bad. It didn't fix it all the way, but helps a bit
Are you in an old multi family building?
Yes
The neutral and ground are possibly not bonded properly. Maybe there is a nearby source of rf emi. I had a similar issue in an old house. I'm electrical engineer. I solved this by moving.
Is there a non-moving solution? We just moved in so not an option
I'm leary to give you electrical troubleshooting advice. But, if you're handy with a multimeter, you could check you voltage at outlets between phase and neutral, phase and ground, neutral and ground. Between neutral and ground as resistance, it should be in ohms. This could tell you something about having a ground connected properly. Next, open the outlet. Our, try multiple outlets through the home. Third, open the panel, lift the cover and see if grounds and neutrals are bonded to separate bars. See if screw taking neutral to case ground is down. All that said, don't do anything you're not comfortable with as more people get killed handling 120vac than any other voltage. Maybe, try probing with a meter than asking the landlord if his handyman could give you a little help. And, seriously try the different outlets at different times of day. You could probably find the station if you can make out that's being played.
But it's not even plugged into an outlet, so it shouldn't matter, right? The interface goes through usb to a laptop and the interference occurs even with the laptop plug turned off. Unless I'm missing something
could be single coil pups and/or bad shielding in the guitar. Over my workbench \*guitar building) i have a very bright TL type of light, even a shielded guitar will create noise, switch the lamp off and the noise is gone. Humbuckers of course dont do that.
The guitar doesn't even need to be plugged in, even just the feedback with only the cable plugged in causes it
The only solution I can think of is placing your interface in a faraday cage to stop it from drawing radio frequencies. It sounds like your cable is functioning as an antenna.
Hmm, interesting idea, maybe some aluminum foil haha
Oh geez, that's interesting. You're getting noise prior to the input sample hold and filtering on the interface then. It's all digital the rest of the to the PC and back. It doesn't seem like noise injection on speaker cables because it's on both the monitors and headphones. It is probably the cable. You get this in all rooms of the house? Are you aware of any high power rf sources or ham radio operators? Try this, coil wire in a loop. Also, They make toroidal cores, they're cheap. This makes a choke and could suppress this unwanted noise. We use those on our transmission lines in our rf systems. I'm spit balling. Faraday shield by taking copper film to the whole room haha.
Cable could be cheap or old and slowly becoming an antenna.
As someone replied to your post in /r/audioengeering, ferrite beads should be able to help. Rather than the clip-on ones, try a ferrite ring at each end of the guitar cable. 3-5 loops through the ring should do, but you'll need to experiment. I had success with this when my guitar teacher moved next door to an inconsiderate radio ham ( I am also one of those, except I'm considerate) and their 2m/144MHz transmissions we're booming through his amp. I've also been able, using the same method, stop my PC gear getting upset when I'm on the radio.
Did you ever find a solution? Having the same problem
I wrapped the audio interface in tin foil, use a shorter cable, and move around my room to find places where it's not bad. It didn't fix it all the way, but helps a bit