Ground Loop hum or induced noise in amplifier

[ljberbi]

Hi guys: I must consult with experts with regard to my problem here and seek any advice that may help. Is there a ThomasW out there? I heard he may be able to offer some advice. If anyone knows Thomas and could send my post to him it would be greatly appreciated. Please read my attached document. Thanks

[cjd]

what's your problem?

C

[---k---]

for those scared to open a word doc (rightfully so)

Ground loop issue or induced noise, what the heck is going on? 12-12-07


Moved guitar amplifier to different room 15 to 20 feet from previous spot. Getting very objectionable hum noise from amps in the new room with all guitars 90% of the time. Both rooms are upstairs in the home. So far have tried several tests and remedies with no success. First moved the amp back to previous room to be sure the noise was not there and it was not. Also ran an extension cord from outlet in previous room to new room as a test and much to my surprise the noise was there, which led me to believe this noise is being induced, as the test would seem to indicate. This begs the question, can ground loop hum be induced into an amplifier or is it through the a/c line receptacles only? I think there is a high potential for ground loop hum in the new room because I have determined the receptacles are on different circuits and the ones I am plugging into are on the same circuit as my den downstairs believe it or not. Tried plugging into every receptacle in the room and the noise is still there even know some of them are on different circuits. Because I suspect the noise is being induced into the amp the next thing I did was get rid of all the dimmers in my house, and that did not help. There are no fluorescent lights, or anything else I know of in the house that would cause induced noise into a/c circuits. I continue to suspect a ground loop issue in the room because I know that is the most likely cause for this type of noise, but my test described above would almost prove this not the case as the noise is still there using the receptacle from the previous room with the amp in the new room. This is why I suspect the noise is being induced (?) I am tempted to have a dedicated circuit ran from the load center but do not want to spend the money if the issue is not a ground loop. I will continue to try other experiments in hopes of identifying the issue because this is just killing my tone. The thought has crossed my mind maybe there is radio waves from a tower cruising through my room or something, the theory sounds kind of crazy but you never know. I am very aware that a certain amount of noise is typical especially with single coil guitar pickups, but the level of noise I am experiencing is a highly excessive as compared to typical

[chasw98]

From what you describe, it does not sound like you have a 'ground loop' but that you do have induced noise and interference. If you really want to get serious and see if this is being caused by something in your house, try this.

Shut down every circuit breaker except the breaker to the room where you have no noise. Second, make sure and unplug anything plugged into the receptacles throughout the house (paying particular attention to items like refrigerators and air conditioners, etc.). Third turn on your amp and guitar (using the extension cord) in the room with no noise and verify that you have a quiet signal. Fourth, move the rig to the room that has a problem and turn it on to see if the noise is there.

If there is no noise when you have moved from the first room to the second room, then you can go about powering up your house and seeing what affects the noise as you turn on circuits and appliances throughout the house.

If the noise is there when you move to the new room with your house powered down, you definitely have external interference that is being caused by something locally outside of your house. It could be a radio station signal, cell phone tower or something like that. These items are not supposed to cause interference and if they are, they probably need to be looked at by the cell techs or radio engineers.

As a last resort you can hire a consultant to do a spectrum sweep and find out where the interference is coming from but I believe you will find that something in your house plugged into a circuit is causing your problem. And it might not even have to be turned on, just plugged into the wall!

[Dave Bullet]

How many mains powered devices are you using?

Are they all grounded / earthed?

If you have a mixture of grounded & non-grounded powered devices in your setup it is possible you have some level of ground loop hum. To reduce this, ground all ungrounded components (ie. wire a plug with the earthing pin and attach to bare metal of the chassis of your ungrounded mains powered component)

David.

[PMazz]

Some of the fluorescent bulbs made for regular sockets cause noise in the lines.