Home Theater Hum

[heimdm]

My setup involves an Anthem AVM60 connected via XLR cable to Anthem AMPs (MCA-525 & MCA-325). My problem is I am getting a faint hum, which is really annoying. I have used an extension cord to plug everything into a single power strip to eliminate ground loops. But the issue has persisted. I purchased an Ebtech HE-8-XLR, and the hum is still there. The only way I can get rid of the hum is to turn off the circuit breaker that powers the outlet to my AVM60 and TV. The XLR snake cable and the power is separated by a stud in the wall cavity. Is there anything else that can be done to avoid opening up the wall and rerunning the power cable?

 

[lovinthehd]

You have cable service or similar? Did they ground properly? Maybe some thoughts for you here https://www.audioholics.com/home-theater-connection/ground-loops-eliminating-system-hum-and-buzz

 

[heimdm]

I do not have cable tv. Everything is streaming. All that is plugged into the amp is a PS4, Samsung Q80 tv, and Roku.

 

[slipperybidness]

My setup involves an Anthem AVM60 connected via XLR cable to Anthem AMPs (MCA-525 & MCA-325). My problem is I am getting a faint hum, which is really annoying. I have used an extension cord to plug everything into a single power strip to eliminate ground loops. But the issue has persisted. I purchased an Ebtech HE-8-XLR, and the hum is still there. The only way I can get rid of the hum is to turn off the circuit breaker that powers the outlet to my AVM60 and TV. The XLR snake cable and the power is separated by a stud in the wall cavity. Is there anything else that can be done to avoid opening up the wall and rerunning the power cable?

Can you clarify, does it sound like the "60Hz hum"?

Does the hum volume change with audio volume? Or is it always the same level independent of volume settings?

 

[heimdm]

I think its more 60hz hum like. The volume level is constant regardless of the volume I set.

 

[slipperybidness]

I think its more 60hz hum like. The volume level is constant regardless of the volume I set.

Is your amp a 2 prong cord or a 3-prong?

If it's a 3-prong, I would start troubleshooting with a "cheater plug" to lift the ground pin. Note that this is defeating a safety device (i.e. you remove the safety ground), so proceed at your own risk, and don't leave it connected like that. If the hum is gone, then you know that you have a ground loop and you can start taking actions to eliminate the ground hum.

 

[heimdm]

I have the XLR connected through the Ebtech HE-8-XLR. I did try the cheaper on the AC side of the AV receiver, and got nothing. Does connecting the "chassis ground" impact the ability for balanced XLR to negate noise?

 

[slipperybidness]

I have the XLR connected through the Ebtech HE-8-XLR. I did try the cheaper on the AC side of the AV receiver, and got nothing. Does connecting the "chassis ground" impact the ability for balanced XLR to negate noise?

try the cheater on the power amp

 

[AcuDefTechGuy]

In my previous house, there was NOTHING I could do to eliminate the hum except to use the "cheater plug" to remove the Ground Prong on the plug.

So I bought a GFCI from Amazon and plugged the Cheater Plug into the GFCI.

https://www.amazon.com/Replacement-Assembly-Interrupter-Protection-Conditioner/dp/B077FV6RQT/ref=sr_1_1_sspa?keywords=Fault+Plug&qid=1568986947&sr=8-1-spons&psc=1&spLa=ZW5jcnlwdGVkUXVhbGlmaWVyPUExMTJXQ01XMVI1MVlVJmVuY3J5cHRlZElkPUExMDI4NzQxMTBPVEw4Qks3TjVCTSZlbmNyeXB0ZWRBZElkPUEwMDEzMDYwMVA0MTVNWVUzVUlUOCZ3aWRnZXROYW1lPXNwX2F0ZiZhY3Rpb249Y2xpY2tSZWRpcmVjdCZkb05vdExvZ0NsaWNrPXRydWU=

In my new house, there is no hum at all.

 

[heimdm]

The amplifiers (Anthem MCA-525 & MCA-535) are just 2 prong

 

[highfigh]

While those plugs adapters do lift the ground, that's not their intended purpose, which is to alalow a 3 prong plug to be grounded when the outlet only has two slots. The green tab or wire is supposed to be screwed to the junction box via the screw that holds the wall plate in place.

That being said, be careful in how many pieces of equipment are touched while using this adapter- if the chassis of something becomes electrically 'hot' and you touch something that's grounded, YOU become the load and that can be lethal.

To test this system-
Connect the power cords as intended before starting, without any cheater plugs.

Disconnect the XLR cables between the Anthem and the amps. Listen for hum- if it's gone, turn off the power to one amp, reconnect the cable and turn it on- if the hum is still gone, do the same with the next amp. If the him is still gone, connect another amp. If the hum returns, disconnect one of the previously connected amps and try again. If it stops after either previous amp is disconnected when everything is connected to the same outlet, through nothing but some kind of unfiltered power strip, you may have slight resistance on the neutral and/or ground connection. Ground loops are caused by voltage differences (called difference in potential or potential difference- electricity is Potential Energy),which causes the electricity to make up the difference wherever it can- if it happens to be on the audio cables, it really doesn't care- it wants its connection.

Your amplifiers and AVM60 all have a ground screw on the rear panel for a reason- use them.

 

[heimdm]

In regard to the ground screws, everything in the house has pex/plastic pipes. What is the best way to connect it to ground? Should I run a wire to the electric boxes ground bus?

 

[highfigh]

BTW- the equipment isn't grounded to the electrical system in your house just because it's plugged into a gorunded outlet- that assumes great connections between the outlet, wiring, electrical panel and connection between the grounding rods(s) and the ground where they were driven into the Earth. There's a connection at every receptacle between the AV system's outlet and the panel, unless that circuit is dedicated and unbroken by splices. Resistance at any point between the AV system's outlet and the panel can affect grounding, especially if there's a projector or TV connected to a different outlet.

 

[highfigh]

In regard to the ground screws, everything in the house has pex/plastic pipes. What is the best way to connect it to ground? Should I run a wire to the electric boxes ground bus?

I don't care about the plumbing- the screws are for bonding the system (making it equipotential, which means there's no measurable voltage or resistance between each chassis when measured from a common point). Adding ground connections is a really good way to have more grounding problems- you want one main path to ground from the panel and each circuit needs a clean path to the panel, without resistance on either the Neutral or Ground wires. If you see something about 'star grounding'- this isn't a physical topology, it's an electrical phenomenon. As long as there's no resistance or voltage between each piece, the locations of the ground is immaterial unless something between the grounding points is injecting noise.

The National Electrical Code makes a distinction between Neutral and Ground wires- one is called the 'grounding conductor' and the other is called the 'grounded conductor'.

https://c03.apogee.net/mvc/home/hes/land/el?spc=foe&id=4672&utilityname=lansing

Sometimes, connecting the separate pieces of equipment to each other is all that's needed and sometimes, you need to use unbalanced cables to get rid of the hum. I had to do that with a Krell AV preamp an power amp because the electrician didn't follow by instructions. The system I installed was noise-free after I connected the unbalanced cables.

Grounding and bonding communication equipment-

https://www.fiberoptics4sale.com/blogs/archive-posts/95043014-what-is-grounding-and-bonding-for-telecommunication-systems

 

[highfigh]

The amplifiers (Anthem MCA-525 & MCA-535) are just 2 prong

But they have ground screws. Read the links I posted.

The reason the amps don't have grounded plugs is because the wire connected to Pin 1 in the XLR plugs and jacks is supposed to maintain ground path for the signal cable's shield- again, without voltage or resistance between them. This pin IS NOT directly connected to the chassis, it's supposed to measure about 50 Ohms between these. If they're directly connected, it's possible that the Anthem aren't truly balanced/low impedance circuits- several companies use XLR connectors because people want to see them but they all include unbalanced connections, as well, because sometimes, they work best WRT hum and noise.

The AVR or Preamp is supposed to be the one grounded piece in the system and using two prong plugs generally ensures this. Often enough, something causes hum, anyway. Sometimes, it's necessary to lift Pin 1 in order to eliminate hum, but it's necessary to make sure no voltage is measurable between any chassis and another.

Modern Recording had an article called 'The Pin 1 Problem', which addresses this and now, a website exists for it, as well as many other articles-

http://pin1problem.com/

 

[heimdm]

I could install bus bars in each equipment location and tie them to the electrical ground. Based on what @highfigh would it be just as good to connect all the ground chassis screws together so they have the same ground?

 

[highfigh]

I could install bus bars in each equipment location and tie them to the electrical ground. Based on what @highfigh would it be just as good to connect all the ground chassis screws together so they have the same ground?

It's not a high voltage and for this, wire gauge isn't important. Read the articles.

You can speed up the process by connecting one end of a piece of scrap speaker wire to the AVM60's ground screw and touching the other end to the ground screw on each other piece- if it stops the hum, make the connection and if not, continue. Touch it to the shield for one of the RCA jacks, too. Do this with the source equipment, as well- sometimes they need to be grounded better, to the AVR or processor.

Make sure the power cords are fully inserted in the receptacle on each piece of equipment.

 

[slipperybidness]

While those plugs adapters do lift the ground, that's not their intended purpose, which is to alalow a 3 prong plug to be grounded when the outlet only has two slots. The green tab or wire is supposed to be screwed to the junction box via the screw that holds the wall plate in place.
.

This is true, but this also makes the assumption that you will get a proper ground on that wall plate screw. May or may not be a good assumption, best to verify.

 

[highfigh]

This is true, but this also makes the assumption that you will get a proper ground on that wall plate screw. May or may not be a good assumption, best to verify.

Definitely true about the assumption.

 

[heimdm]

My outlets are Lutron, so there is no metal screw for the cheater to plug into. I did run (avm60->mca-535) some thermostat wire 18 gauge that I had. It's not perfect, but it seemed better than it was. If I listen real carefully, it sound like some faint white noise. I am thinking once I get a perm ground wire installed, then I should rerun the Anthem Calibration software. I was looking at the wiring really closely, and since the wiring runs down the wall and the XLR cables are close to the wall when they are plugged into the amp. Is that a material that would block the electrical interference from coming through the wall? The wall is just plywood.