Guitar amp emits buzzing noise... HOWEVER....?

Question

HOWEVER, to add to the title, only when my laptop is plugged into a socket. Let's put it like this:

When my laptop is charging (plugged in) my amp emits this noise. Then when I touch a metallic part of my laptop, this noise stops.

When my laptop charger is unplugged, my amp stops emitting this noise. Then, when I touch a metallic part of my laptop, this noise starts. What's the problem here? I plug my laptop and amp in the same.. uhm (forgot the name) it's this rectangular box with 4 sockets in it, directly connected to the socket in the wall.

Answer 1

It sounds like a grounding issue with your house wiring. One thing that sometimes helps is to plug a power strip into the wall socket, then plug both the amp and laptop into the power strip. That way, both devices are plugged into a single receptacle. This is a trick we use on stage if we're getting bit by the microphone.



Grounding doesn't explain why the laptop causes interference when it's NOT plugged into the wall. Electronic devices are certainly sources of radio interference...that's why they all have FCC tags on them. If this is the case, the noise should be reduced by putting distance between the amp and laptop.

Answer 2

If you amp buzzes then it could be the ground. Try using a 3 prong to 2 prong converter on the end of the plug. (these are mostly gray and cost about $1.00) Or is could be a short in your cord that plugs your guitar into the amp. This can happen if the cord had been wound up, or gotten tangled up, or even steped on. Also having something plugged into the same socket as your amp can cause this. Try a power bar. If these don't fix the problem there is a defuzzer that you can get at your music store or Radio Shack that will do the trick. However they can be costly. Good Luck

Answer 3

Your laptop power supply most likely has a switching mode regulator which is emitting a bit of radio frequency noise. Likewise, your laptop has many high speed digital signals which create radio frequency noise, some of which can escape the laptop. Touching your laptop causes your body to become an antenna and radiated this leaked energy more efficiently. All of this is pretty normal for electronic gear.



The culprit is your amplifier which is picking up these radio frequency noise signals and injecting them into the signal path in the amplifier. I have a Crate amplifier that has this problem severely when I plug it into an inverter for outdoor use. I installed an EMI (Electromagnetic Interference) filter at the power inlet to the amplifier which reduced the noise quite a bit. The noise can enter your amplifier in two ways: radiation, and conduction (through the AC power line. Adding an EMI filter to the power input will help with conducted interference. Shielding the amplifier circuits with conductive sheet metal or heavy gauge aluminum foil will help with radiated interference.



Unless you are skilled in working with electronic equipment, I don't recommend you attempt the shielding approach. You might try plugging the amplifier and the laptop into separate outlets which are on different branch circuits in your house. The longer electrical path between the amplifier and computer might attenuate the interference signals enough to improve the situation.

Answer 4

Normally its a grounding issue, and as your laptop and amp are sharing the power strip your getting some type of interference from the laptops power supply by the sound of it, a quick cheap test would be to purchase a 3 to 2 prong outlet adaptor and see if that cures the problem, this takes the ground out of the equation, if it does and your planning to play in the bath tub or are worried about electrocution you can go out and buy a ground suppressor, they cost anywhere from $50 to $100 dollars, personally I just keep dry and use the adaptor, as my florescent lights were the cause of my buzz.