Speaker Hum

@jdm11

It also might help us diagnose the problem if you gave us a few more details, like:

-equipment connected via RCA or XLR or both?

-how many pieces of audio equipment have 3 prong AC plugs, how many have 2 prong AC plugs?

-how long your RCA cable runs are?

-generally speaking (or you can get specific) how many and what pieces of audio equipment are interconnected?

-is all audio equipment in the same room?

Those are right off the top of my head.

@jdm11 

So since the EVO 300 has all RCA ins and outs, I'm assuming all equipment is connected via RCA cables. Correct? 

Disconnect the internet/tv cable from the cable box or/and modem.

Still waiting to hear from you if this made a difference. To be clear, disconnect the coax cable from the cable company, so it makes no connection to your modem or cable box. 

Looking on the back of the OneR's, I can't tell if there's 3 prongs in the AC socket or just two? I think it's two, but please correct me if I'm wrong.

Is it safe to assume the OneR's still reproduce sound if they aren't powered (ie, plugged into an outlet)? I understand the sub sections of them will not work, but does the rest of the speaker system work? If they still reproduce audio without the subs functioning, is the hum still there? Also, just try unplugging power to one of them, and see if that changes anything.

@jdm11

unplug the HDMI cable to your tv from cable box.

As articdeth suggested, this would be easier than disconnecting the coax cable from the modem or cable box, but if that doesn’t do anything, at some point I would try disconnecting the coax cable to the cable box or modem.

Also when I moved in I had every outlet in the house with new GFIs - would the electrician have noticed if the box / grounding in the house was off or not necessarily?

Most GFCI’s will not work correctly without a ground. Yes, they make ones that work in situations where a ground doesn’t exist, but if you had any of those, he would have had to install specific GFCI’s for that application. If this were the case, I think he would have mentioned this to you. Hard to say if he would have pointed out any other electrical abnormalities. Some houses that were built in the 60’s contained aluminum wiring instead of commonly used copper. Do you remember him mentioning anything about this to you? Not every house in the 60’s was built with aluminum, but it was more popular during that decade than any other.

Maybe I need to disconnect them all from the amp as well or that doesn’t make any sense?

YES! Definitely try that! If THAT fixes the problem, try plugging them back in one source at a time, and see when the hum starts again.

@erik_squires 

all GFCI outlets will work without a ground

You are correct. I never knew that before. Thanks for pointing that out! The situation could be very deceiving for some (especially audio-enthusiasts plugging their audio equipment into GFCI's that they think incorporate a true earth ground), since the GFCI will trip when needed, even though a true earth ground may not be present on the particular GFCI.  

@erik_squires

any audiophile moving into a home needs to do a thorough inspection.

Totally agree, and I too also recommend and encourage it be done. In addition to running some new circuits, I replaced all switches and outlets in my home when I moved in 21 years ago. Yeah, I too hate the back stabbed method of connecting outlets or switches. None currently exist in my home, and when doing maintenance work anywhere else, I never ever use that method of connection.

If you look at my virtual system pictures, you’ll see the meter I use to measure my home ground system resistance (which measures under 1 ohm). It’s a meter I also use in the radio broadcast industry to measure ground resistances in broadcast facilities.

@jdm11

-Do you have the ability to take the amp to another location (with headphones), and try it there?

-Before you call an electrician, I would try turning off all circuit breakers except the one that powers the amp.

-I’m wondering if you have a ground and neutral switched inside the house somewhere.

-jetter suggested trying a cheater plug (3 prong to two prong adapter). If you haven’t already tried it, I also recommend doing that before calling an electrician.

-erik_squires recommended purchasing an outlet tester (pretty much any brand or type purchased at Home Depot or a hardware store will do), and plugging it into your outlets for testing them.

-Are you noticing any other electrical abnormalities in your home?