EMI from power wiring in old house

[Harooncr]

So I have an interesting problem: Extreme EMI radiating from the power wiring in my house.

I bought a house here in the USA that was made in 1948. A lot of the wiring is original, some has been updated. However, whenever I plug in my guitars anywhere, they pick up an extremely loud 60Hz hum. The tonal characteristic of the hum changes depending on where I point the guitar, picking up different amounts of the dirty harmonics. It's present in every guitar, even the unplugged audio cables.

Here's the tricky part: I can turn off every circuit in the house except 1 dedicated outlet underneath the main panel, and the hum is still there. That leads me to think that the hum originates from the AC power lines leading INTO the house from the utility line. That would make sense because I live pretty close to some gas stations, and I think I share the same power as they do. I'll be doing some more experiments (get a Hum Exterminator, wander around with an AM radio, etc). The only solutions I can think of are to entirely rewire the house, or get several dirty electricity filters.

In the mean time, does anyone here have experience with similar issues?

 

[Toopy14]

Did you try using another isolated circuit to eliminate the possibility of the one circuit/outlet you used being the culprit?

If so, contact the local utility, let them know what is happening and the troubleshooting you did. They will come and test the lines coming into the house to see if the power is clean or not. Could be an issue with a step-down transformer, feeding your house/neighbourhood. The utility is responsible for the power to the demarcation point...ie., at the meter base.

 

[Greg Ferguson]

In the mean time, does anyone here have experience with similar issues?

Since misery loves company…

Yes. I'm in a house from the late 30s with the same problem and that had been subjected to years of hacks and not-to-code changes resulting in three power distribution boxes and two sets of breaker boxes. Rooms have two outlets only and some of the outlets, such as in my guitar room, have been converted to grounded receptacles, but I doubt the wiring itself was updated, and it definitely wasn't done to code.

We brought in an electrical engineer a couple years ago, who tOOOOtally rewired the feed from the power company, consolidating the boxes so all that's to code now, but when I asked about whether it's possible to do the rest of the wiring he shook his head and said it wasn't worth it. The house is all adobe, with rock-hard walls that are a minimum of 12" thick. Drilling through them or cutting channels for wiring to code was going to cost a stupid amount and result in conduit outside or gouges in the walls, so we live with two outlets in the rooms, and I put up with EMI. I've considered building a Faraday cage in the room, but it's easy to imagine the look I'd get for that so… unh-uh.

Big monitors and computers with clear sides don't help. I use an iMac Pro, which is supposed to have an EMI shield behind the display, but I think the real problem is elsewhere because the problem doesn't go away when I power down the entire computer rig and drives. The basement is where all the power runs into, and the furnace and A/C exchange and blower is, and power feeds to every corner of the house go from there, and that's just a room over and down a floor, so maybe 20 feet.

EMI leaks into the humbuckers and the single-coils but I've found where to position myself that will almost stop it, and switch positions 2 and 4 are my friends on my Strats. I know my gear doesn't pick up noise when I'm playing out, so I reconciled myself to dealing with noise at home.

 

[Greg Ferguson]

Did you try using another isolated circuit to eliminate the possibility of the one circuit/outlet you used being the culprit?

If so, contact the local utility, let them know what is happening and the troubleshooting you did, they will come and test the lines coming into the house to see if the power is clean or not. Could be an issue with a step-down transformer, feeding your house/neighbourhood. The utility is responsible for the power to the demarcation point...ie., at the meter base.

Good point about the power into the house.

As I said above, our house is from the late 30s. It was one of the first into the neighborhood, which was one of the prime locations in the city back then, so they got electricity from when the development began. I kinda doubt the utility company installed better lines or transformers just to improve things because it was the right thing to do, only if something was broken.

 

[fractalz]

Our 1950s era home in California had terrible EMI coming in from the outside. It was either a transformer or the new smart power meters (with cellular connection to the mothership) or some neighbors equipment. When I had a chance to design and build a new studio in Portland, OR, we did the Faraday cage approach:

https://kingshillsound.com/2019/04/09/studio-build-emi-abatement/

Things are much better and more controllable but, guess what, the call can also come from inside the house! There is still EMI radiating from equipment in use and it remains a challenge to reduce the noise floor. But, it's mostly controllable. Mostly.