Electromagnetic Interference - Help!!

Zwiebelchen said:
That actually shouldn't happen, except if you cable has a magnetic pickup. ;)
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Actually, it can happen if the interference is strong or there's a bad connection in the cable. That's why you also want to test with the cable unplugged from the Axe's front panel.
 
Rex said:
Actually, it can happen if the interference is strong or there's a bad connection in the cable. That's why you also want to test with the cable unplugged from the Axe's front panel.
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Compared to a magnetic pickup, the effect should be negligible. From what I take from the TO's description, the interference seems to be just as strong with and without a guitar connected - which tells me there's something fishy going on.
 
Rex said:
What happens to the noise when you unplug your guitar cable from the Axe's front panel?
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No noise.

Zwiebelchen said:
That actually shouldn't happen, except if you cable has a magnetic pickup. ;)

Have you tried using a different cable?
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Yes, but not without my guitar plugged in. I'll try some others w/o the guitar.

Zwiebelchen said:
Do you have a WLAN router in your house? If so, have you tried turning it off? Just asking, because sometimes the most obvious issue tends to be forgotten...
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I do have a wireless router.... as a matter of fact, it's in my studio. I have not tried turning it off yet. I will try this.

I have also not gone through the process of shutting down and troubleshooting all my circuits in the house. I have shut off lights, computers, etc. but I plan to dive in deep here soon.
 
Warrior said:
I do have a wireless router.... as a matter of fact, it's in my studio. I have not tried turning it off yet. I will try this.
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Aaaaaaand we found the culprit. Funny how everybody keeps forgetting about the largest source of EM waves when tracking down such issues... ;)
 
Rex said:
What happens to the noise when you unplug your guitar cable from the Axe's front panel?
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Zwiebelchen said:
That actually shouldn't happen, except if you cable has a magnetic pickup. ;)

Have you tried using a different cable?


Do you have a WLAN router in your house? If so, have you tried turning it off? Just asking, because sometimes the most obvious issue tends to be forgotten...
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Zwiebelchen said:
Aaaaaaand we found the culprit. Funny how everybody keeps forgetting about the largest source of EM waves when tracking down such issues... ;)
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I'll turn that baby off and see how it goes.

So is it likely this would mean I just need to move it away/out of this room?
 
Zwiebelchen said:
That's definitely the first thing to try. Just taking it out of the room might not be enough, though. You'd definitely need a lot more distance.
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Well.... I guess the first order of business is to confirm that it is the source of the EMI. If so, I'll get that bugger moved.

When I was doing my AM radio EMI detecting the radio didn't pick up any interference coming from the router.
 
Right. It's also not an RFI problem - you can't hear RFI. Frequency is much too high. Noise is almost always power-line related EMI, and almost always involves a transformer as they rely on magnetism to operate. That field is what your guitar pickup and/or cord picks up.

Power supplies are notoriously noisy. Simply turning off routers/monitors/effects/etc. often won't tell you much because the power supply is still live. For instance, TVs are always live. Turning them "off" basically just blanks the screen and mutes the audio amp. The TV is still alive. Otherwise, the remote wouldn't work. Also, wall warts never shut off, so you can disable the equipment they power, but the supply is still running. Surprisingly noisy little bastards. Best way to beat them is to use an outlet strip to fire them up and turn that off rather than the equipment. Motors are also big radiators. Where's the A/C unit? Where's the furnace? Compressor/blower motors will put out big fields, as they also rely on magnetism to operate.
 
You can't rule out RFI (which is actually a flavor of EMI). There are lots of opportunities for rectification and other things to occur that can make RFI audible.
 
You're right, of course, but on the list of things to go in search of when interference is a problem, RFI is pretty far down the list.
 
Cagey said:
You're right, of course, but on the list of things to go in search of when interference is a problem, RFI is pretty far down the list.
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RFI might be a more common source of noise than you think. As others have noted, wireless routers can play heck with your guitar signal, and they're all about RFI—no audio-frequency output at all.
 
Rex said:
RFI might be a more common source of noise than you think. As others have noted, wireless routers can play heck with your guitar signal, and they're all about RFI—no audio-frequency output at all.
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I agree that RFI can be a problem, the OP he pretty much ID'd the noise source (computer screen) and I would bet the power supply running the router would be a more likely culprit if it were still an issue with the computer unplugged. RF broadcasting at 2.5 gigs it's unlikely your going to hear that in the guitar signal and if you could it would be extremely high pitched depending on the carrier freq. and type of transmission used typically QPSK or QAM.

My computer is sitting less than a foot from my router (wireless) and the Axe and guitar are with in 5 feet of that. When I play sitting next to the screen (iMac) I do get 60hz noise. With two cooling fans and an HDD and power supply running that's a lot of EMI for a pickup to grab on to.
 
Agreed—it could well be the power supply. But RFI is a common culprit. Example: if I hold my guitar right next to my Wi-Fi AP, I get hellacious noise. The AP's power supply...not so much. And it's not the 2.5 GHz you hear (no one can hear that :) ). It's all the BS impressed on that signal. It rides the RF carrier into your gear.

By the way, how's that hand coming along?
 
Try moving your guitar around the room with the noise gate off. Listen for when the noise gets worse and when it doesn't. Sometimes you can locate the source by using your guitar as a detector.
 
Check to see if the interference kicks up when the refrigerator cycles or the air conditioning/heating kicks in. They're riding household current and have big motors. They can introduce a lot of noise and they're such routine things we forget they're even there.
 
Rex said:
Agreed—it could well be the power supply. But RFI is a common culprit. Example: if I hold my guitar right next to my Wi-Fi AP, I get hellacious noise. The AP's power supply...not so much. And it's not the 2.5 GHz you hear (no one can hear that :) ). It's all the BS impressed on that signal. It rides the RF carrier into your gear.

By the way, how's that hand coming along?
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Roger Dat!

The hand has fully recovered with only light scars ;).
 
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