I have an Epiphone Les Paul Junior. I 'm plugging in to the computer through a Scarlett Solo USB. It hums so bad its unplayable. Even when I'm touching the strings. I checked the electronics on the guitar and everything looks good. I will say that the screws and pickups look a bit rusty. Could that be the problem?
What is causing major humming from my guitar whether plugged into my amp or my computer?
No answer at all, but my sympathies for "a hum"... I've had that before, and never did figure it out. Perhaps people here can figure it out... but/and you'll probably need to give more info. Perhaps interactively when knowledgeable people ask for clarification.– paul garrettApr 17, 2022 at 3:50
First simple thing to check are the leads. Poor quality leads and their soldering are often the cause of problems. Eimination - try a different guitar, try guitar through a different computer, etc.– TimApr 17, 2022 at 9:19
2If it's a laptop, try it on battery only. Unplug any peripherals that use mains too. Switch off any fluorescent lighting or old style TVs/displays [CRT]– TetsujinApr 17, 2022 at 10:14
1Electronic interference. Try moving different bits of gear around and see if something is not causing the hum.– Neil MeyerApr 17, 2022 at 11:55
1Does the hum reduce as you move further away from your computer?– CorsakaApr 19, 2022 at 11:46
One of the largest causes of hum in a guitar is an internal ground loop or a faulty ground connection. I'm going to break the mold here and say that your problem is most likely the guitar and not your setup.
If you open it up, check for frayed wires, broken solder joints, and double-check the wire going to your bridge and tailpiece. If you aren't comfortable opening up your guitar to diagnose the problem I recommend you watch some youtube videos (there are many on this specific problem) or as a last resort, find a guitar tech.
You can also check to see if the shielding paint in the cavities is grounded, If you have any bare wires touching the shielding paint other than the one placed there to ground it (It should be secured well) those might also be the issue.
It would be much easier to find the problem if you could specify what type of hum. 60 cycle hum is annoying, but subtle, if it's 120hz hum (a little buzzier) then you probably have a ground loop.
Your location might also be a problem, are you surrounded by anything that might produce large-scale 60hz signals (ex. a power station or really anything big that runs on electricity)?
Does your setup look something like this? This would be the perfect setup for a ground loop. I had a similar problem with this setup, and the reason was the (inter-)connection from multiple devices via the protective earth.
You can try using unbalanced cables between audio interface and speakers, or try to bypass the earth connection from the speakers. However, the latter can be very dangerous if your speakers have any touchable metal surfaces. If recall there being special hardware, that disconnects the earth safely.
Or, to test, where to problem is, you can try using a laptop in battery mode, disconnected from the power grid, as @Tetsujin writes.
In any case, the humm should (!) disappear, if only one single peace of electronics with protective earth is connected to the power grid.
You shouldn't ever get hum on balanced line [common mode rejection], & having all mains earthed to the same point is as good as it gets in the consumer world. I have a very similar setup here & it is dead silent. The component you're thinking of is known as an isolating transformer. The 'fix', if you do have a huge resistance discrepancy which does actually cause an earth loop in that wiring setup is to strap all the chassis together & earth at one point, removing earths from individual plugs. That preserves electrical safety as well as removing the multi-point potential of domestic mains.– TetsujinApr 17, 2022 at 16:35
In my case the "power socket" is two power strips with multiple hardware plugged in. Only after disconnecting a speaker from earth, it became quite. So I disconnected both and since then, I never had any problems again. Also, I never changed the audio cables, so I know with 100% certainty that I use and used balanced cables. I don't claim to know the cause of the problem of the question starter, I only speak from experience and hope I can help.– PederApr 17, 2022 at 19:37