Ground Loops and Radio Frequentcy Interference.

Hi,

I am starting this thread to collect information about Ground Loop and Radio Frequency Interference. Hopefully it will be helpful for those suffering either or both of these problems.

My experience re Ground Loops. My Wife and I bought a new home. In our old house there was hardly any problems with interference but in the new home I have had hum and crackle in my monitors and have had to turn their volume down quite a bit. Eventually I bought a ground loop isolator that removed essentially all the crackle and almost all the hum even with the monitors at full volume. I would guess hum is reduced about 97%. At least that is how it seems to me. I simply installed the Isolator between the audio interface and monitors.

My experience re RF interference. When I use my Guitar through my amp I suffer RF. You can generally confirm the hum is RF if the sound changes when you move around with your guitar. iIt seems to depend on the time of day or/if I have a computer turned on.

I tried ferrite beads without success and am continuing to trouble shoot the problem. It happens with my Gibsons but not with my Fenders. I am told that is due to the noise cancellation on the Strat pick-ups.

I am hoping others will chime in with their experience.

All the best,
John

Hi tlw,

Thanks for the reply. You must have misread my post about the guitar interference. The Fenders are fine. The Gibsons are the problem. I do turn the computer off for practice, but I need it on to record.

John

You could check for "proper" wiring, i.e. hot, neutral and ground all properly connected through to your wall outlets. A receptacle checker like this can do it. The next thing to worry about is whether you have two different circuits (from two different circuit breakers) feeding wall outlets near your equipment. If you use both outlets, there could be unbalanced current flow, and therefore high 60HZ emissions, heard as hum from any sensitive equipment.
 
There is a different kind of house wiring error that is harder to find, but probably not common. It happens when two different circuits both feed to a distant box (say lights/switches on two different circuits) and have their neutrals joined. This can cause massive electrical noise all along both circuits through the walls, as current is no longer balanced in equal but opposite directions in the wire pairs. When this happened at my house, it was causing CRT monitors to flicker horribly unless all the lights were out. I used an EMF/ELF meter to locate the wires in the walls and find the box where they joined.
 
That same meter spotted massive noise near the outside power connection to the house. That can be pretty common, depending on how the power company's feed interacts with a local ground, making some part of the power feed unbalanced, thus emitting 60HZ EMF.

tlw
Wi-fi can also be a source of noise - usually showing up as a whining at around 2.4KHz and 5KHz, which are the usual bands routers and computers transmit on.

Wi-fi is 2.4GHz and 5GHz. It won't even bother your dog. Not sure about the other frequencies associated with computers - USB and Ethernet should also be way beyond audible frequencies. There may be other stray RF from the components in the case that could cause problems.
 
Transformers that drive LED and other lights can be an issue. These convert mains voltage to 12V DC or similar, and generally sit near the light. I know these can cause noise in my guitar unless I'm using the humbucker pickup.
 
Cheers, Peter.

1. Balance everything that can be balanced. Everything between your computer I/O box and speaker amplifier should be a balanced connection using high quality wire.
2. Shield everything else. If your fenders aren't making noise, then either they're well shielded or making use of noiseless pickups or probably both. When I took my chibson wes paul out of the box (don't judge me) the hum and noise was almost as loud of the guitar itself. Once I changed out the pots and dropped in a set of Seymour Duncans and lined everything with copper, the guitar sounds great and is absolutely dead silent. Even when I kick the pickups into single coil mode. Even with all my computer monitors on and the overhead lighting dimmed.

Cell phones are another potential source of RFI. Their signature is an intermittent buzzing. 

sharke
 I do get quite horrendous buzzing from my Telecaster sometimes. I know they're pretty noisy at the best of times but it makes recording anything with anything more than the lightest of crunch sounds problematic. What I've found though is that there is a "sweet spot" at which I can position my guitar which virtually eliminates the hum. Unfortunately for me it happens to be facing away from my DAW with the front of the Telecaster tilted toward the floor 

I put Lace Sensors in my Tele and shielded the cavities. Solved the noise problems completely and makes the guitar a joy to record with.

z1812
Hi tlw,

Thanks for the reply. You must have misread my post about the guitar interference. The Fenders are fine. The Gibsons are the problem. I do turn the computer off for practice, but I need it on to record.

John

No, I read you fine. I'm just surprised that one humbucker guitar, a Fender, is silent while another, a Gibson, is not. They use exactly the same technology, humbucking pickups, which is one thing that kind of made me wonder if P90s are involved or maybe coil-tapping.

It might be that the Fender is better shielded in the cavities than the Gibson(s). Another is that if you use more gain with the Gibson than the Fender then any noise in the system that's coming in through the guitar is going to be amplified more. Or, more accurately, the compression of the entire signal will raise the noise floor along with the signal.

Hi,
Yes, that is a good idea to move any motors off the 120V phase that is running to your studio wiring (if you can). If you have a good electrician, they can help you accomplish the balancing.
 
Many people are not aware that you have two separate 120 volt phases coming into a typical US home and electricians balance the loads across them for new construction (which is the correct thing to do). However, this usually assures that you have some noisy refrig or air conditioner on the phase as your mic preamp on (another reason to use balanced mic wires). 
 
A recording friend I know didn't realize he had 3 phase coming into his house but after working with an electrician, he was able to set up one phase for his studio, one for his workshop, and one for the rest of the house. He was also able to isolate any 240 motors from the studio line by using the other two phases - sweet!

Now just think if Tesla actually talked Westinghouse into transmitting AC wirelessly - himmmm.
 
Have fun but be safe,
 
h

I would say no as far as the ambient noise floor of the guitar pickups into a preamp section. The more you open the vol pot, the more the noise floor is exposed to the preamp (and is amplified) it does not disappear. If you are playing live at louder levels, once the preamp does it job, and passes the signal to the power amp section, the guitar noise is many dB below the amplified signal so it is not a problem at higher speaker volume levels. However, if you are recording your guitar direct into a DAW, the noise floor is more obvious due to the lower signal levels.
 
Oh yea, and if you have ground loops in the wiring of your guitar (or pedals) and unshielded control cavities then RF and hum may also be exposed to a preamp section (another can of worms). By the way, aluminum duck tape makes great Faraday cages to shield guitar cavities - one roll from Lowes will probably last a lifetime.

Take care,
h

pinguinotuerto
Have you tried a higher end instrument cable with better shielding?

Apart from good wiring/shielding on the guitar itself, the cable cannot be overstated. I do a lot of solo acoustic work and will never use the stage cable, always using my own. All mine are D'addario/Planet Waves, or handmade with Mogami cable. I'm very particular with my tone and this is the first area of let down with cheap cable, plus loss of voltage/gain, which adds to hum/noise. The same applies in the studio when it's time to record, acoustic or electric. I've many noiseless and single coil strats and tele's, used for different sounds of course, but while noise can be a problem with single coil, it's part of the reason I will use it in the first place. Poor cable makes it impossible.
 
Everyone else has pretty much covered the earth loop thing for all the studio gear. It's all about attention to detail and checking all is well with house wiring. cheers. Dave.

Fluorescent lights are notorious for adding noise to electrical circuits.
 
Rocky

Hopefully you don't have any CRT displays. They induce noise into guitar pickups. Flat screens don't have that problem.

z1812

I tried ferrite beads without success and am continuing to trouble shoot the problem. It happens with my Gibsons but not with my Fenders. I am told that is due to the noise cancellation on the Strat pick-ups.

I am hoping others will chime in with their experience.

All the best,
John

Provide the specifics on your GIbson.  Model and pickups.
 
As another poster pointed out, you narrowed the problem down to the guitar.  And Gibson's typically have humbuckers, which by nature are noise canceling.  Unless you have a P90 equiped (which is a single coil) Gibson.