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Topic:
UPS sending hum into system?
This thread has 29 replies. Displaying posts 1 through 15.
Post 1 made on Wednesday December 10, 2014 at 19:58
FreddyFreeloader
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Hey guys. I just finished a nice theater with an APC S10 balanced battery backup solution--> Marantz AV7701-->balanced outs to Outlaw 7700.

There is a 60 Hz hum in the background (does not vary with volume) but can be heard faintly, really only when paused or volume is all the way down. You can hear it in the subs and high overtones in the tweeter.

Problem goes away completely when I power my rack straight from the electrical outlet and not by the APC.

Bad APC? I have tried all the different kinds of outlets on it and connected the ground stud to the rack chassis. Don't know what else to do besides try a different one and those things are a back breaker when you fly solo!
Post 2 made on Wednesday December 10, 2014 at 20:35
Brad Humphrey
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There was a thread on IP about this very same thing awhile back, I think it was even an APC unit.
I can't remember the outcome. May have been the original poster never came back and told us the outcome - I hate people that do that.
But I do remember after all the fact finding and things that were tried, strongly believing it was a defective UPS.
Post 3 made on Wednesday December 10, 2014 at 20:38
highfigh
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On December 10, 2014 at 19:58, FreddyFreeloader said...
Hey guys. I just finished a nice theater with an APC S10 balanced battery backup solution--> Marantz AV7701-->balanced outs to Outlaw 7700.

There is a 60 Hz hum in the background (does not vary with volume) but can be heard faintly, really only when paused or volume is all the way down. You can hear it in the subs and high overtones in the tweeter.

Problem goes away completely when I power my rack straight from the electrical outlet and not by the APC.

Bad APC? I have tried all the different kinds of outlets on it and connected the ground stud to the rack chassis. Don't know what else to do besides try a different one and those things are a back breaker when you fly solo!

What is in the system, but not plugged into the APC? Look at the resistance on the neutral used by the APC and the outboard equipment- you have a ground loop and if you use a "ground lift" adapter, it should be gone. I put quotes on that because that's not what it was designed to do, but t has become the "go to" for far too many people.
My mechanic told me, "I couldn't repair your brakes, so I made your horn louder."
OP | Post 4 made on Thursday December 11, 2014 at 00:47
FreddyFreeloader
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On December 10, 2014 at 20:38, highfigh said...
What is in the system, but not plugged into the APC? Look at the resistance on the neutral used by the APC and the outboard equipment- you have a ground loop and if you use a "ground lift" adapter, it should be gone. I put quotes on that because that's not what it was designed to do, but t has become the "go to" for far too many people.

Everything including projector is plugged into the APC. Only exception might be a Unifi wifi access point POE injector sharing the duplex AC outlet the APC is plugged into. Ethernet cable from Poe injector plugged into switch in rack.

I have tried lifting ground on individual components (not all at once and just audio components and projector) with no luck. FWIW you can also get rid of the hum by unplugging all HDMI cables from the Marantz. Each individual HDMI cable, when plugged into the AVR individually, produces a smaller amount of hum so I couldn't seem to isolate it to a certain path. When they're all plugged in is when it was the loudest.

One last thing I would like to mention that was strange, is that when troubleshooting and looking at at the APC, I started off by bypassing it and plugged an extension cord straight into an outlet in a different room and for some reason the hum got like 10x louder. Tried it back in the dedicated outlet for the rack and it cleared up completely. Wonder what was up with that other circuit and if it's related at all to to my problem.

Thanks for your responses.

Last edited by FreddyFreeloader on December 11, 2014 01:01.
Post 5 made on Thursday December 11, 2014 at 01:30
King of typos
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That APC is a beast, ain't it?

I have a S10 as well, but everything is fine with my set up. I had the cover taken off of it when I received it. Because I wanted to see what was so dang heavy.

With that said, I know that there is an isolation transformer in there. I don't recall how it's wired up though. There is a huge grounding terminal on the back. Perhaps you could connect units to it.

KOT
Post 6 made on Thursday December 11, 2014 at 04:00
buzz
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I always start tracing hum problems by disconnecting the cable or satellite feed. Chronically, these systems are improperly grounded.
Post 7 made on Thursday December 11, 2014 at 05:00
highfigh
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On December 11, 2014 at 00:47, FreddyFreeloader said...
Everything including projector is plugged into the APC. Only exception might be a Unifi wifi access point POE injector sharing the duplex AC outlet the APC is plugged into. Ethernet cable from Poe injector plugged into switch in rack.

I have tried lifting ground on individual components (not all at once and just audio components and projector) with no luck. FWIW you can also get rid of the hum by unplugging all HDMI cables from the Marantz. Each individual HDMI cable, when plugged into the AVR individually, produces a smaller amount of hum so I couldn't seem to isolate it to a certain path. When they're all plugged in is when it was the loudest.

One last thing I would like to mention that was strange, is that when troubleshooting and looking at at the APC, I started off by bypassing it and plugged an extension cord straight into an outlet in a different room and for some reason the hum got like 10x louder. Tried it back in the dedicated outlet for the rack and it cleared up completely. Wonder what was up with that other circuit and if it's related at all to to my problem.

Thanks for your responses.

Do you have one of these? If not, get one and see if the neutral is lifted anywhere in the room. Also, look inside of the breaker panel for signs of moisture.

[Link: amazon.com]
My mechanic told me, "I couldn't repair your brakes, so I made your horn louder."
Post 8 made on Thursday December 11, 2014 at 08:18
Mogul
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Your result with the outlet outside of the room leads me to wonder if there's an improper neutral-to-ground bond somewhere nearby. They can be a bear to troubleshoot and the only way to see for sure if you have one (aside from physically locating it by chance) is to have an electrician take down the house and disconnect the breaker panel from the mains panel where the neutral to earth ground lives and check for continuity between the neutral and safety ground bus. I've found improper neutral to ground bonds in 3 houses in the clothes dryer, where appliance installers have failed to remove a jumper installed by the factory for use with old 3-prong dryer cables. Another common point of improper neutral-to-ground connection is failure to remove the grounding screw from the neutral bus bar in subpanels. It's also pretty easy to shove wiring into an outlet box in such a way that the bare ground doubles up and touches the neutral lug on the side of the outlet.

On a related note...Most hybrid balanced/unbalanced consumer equipment I've encountered has the "pin 1 problem" design flaw. This in itself can amplify even normal electrical system noise and/or EMF to a problematic level. I'd try connecting the amp and preamp with unbalanced interconnects to see if the problem goes away when also connected to the APC. If so, let me know and I'll send u pics of a custom XLR solution that solves the problem.
"Whatever is rightly done, however humble, is noble." [Sir Henry Royce]
Post 9 made on Thursday December 11, 2014 at 08:25
thecapnredfish
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On December 11, 2014 at 04:00, buzz said...
I always start tracing hum problems by disconnecting the cable or satellite feed. Chronically, these systems are improperly grounded.

Could you explain how these are improperly grounded.
Post 10 made on Thursday December 11, 2014 at 10:24
Audiophiliac
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We insalled that Marantz and connected it to a Krell Showacase 5 channel amp via XLR and had nasty hum as you described. We also had the same hum, but a bit lower in volume from the LCR which were active M&K speakers, connected to the Marantz with unbalanced interconnects. We could not fix it completely. Marantz tech. support told us to use a Marantz amp because they had not had any noise in their experience with both products. Brilliant, eh? Reviews across the interwebs complained of humming and buzzing with the Marantz 7701, so we returned it and put in an Anthem AVM50v and no hum. And surprisingly, no HDMI issues. :P
"When I eat, it is the food that is scared." - Ron Swanson
Post 11 made on Thursday December 11, 2014 at 10:56
Ernie Gilman
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On December 10, 2014 at 20:38, highfigh said...
What is in the system, but not plugged into the APC?

On December 11, 2014 at 00:47, FreddyFreeloader said...
...Only exception might be a Unifi wifi access point POE injector sharing the duplex AC outlet the APC is plugged into. Ethernet cable from Poe injector plugged into switch in rack.

While this should not be a problem, you also should not have hum, so look into things that should not be problems!

I have tried lifting ground on individual components (not all at once and just audio components and projector) with no luck.

So you didn't unplug the video components, such as your satellite receiver, cable box, DVD, game, Roku, etc.? Just the CD player and the dual cassette? An actual list of what you've got, plus a list of what's not in the same room, might be helpful.

FWIW you can also get rid of the hum by unplugging all HDMI cables from the Marantz. Each individual HDMI cable, when plugged into the AVR individually, produces a smaller amount of hum so I couldn't seem to isolate it to a certain path. When they're all plugged in is when it was the loudest.

Really strange! I think you should follow the advice regarding grounds and neutrals in the house. This is a very squirrely problem!

In passing let me note that every system has oodles of actual ground loops. A CD player with analog connection has a ground loop between the two channels. The thing is, we never think about what ground loops exist until we have hum, and then we ignore the mass of such connections, making it hard to find the problem.

One last thing I would like to mention that was strange, is that when troubleshooting and looking at at the APC, I started off by bypassing it and plugged an extension cord straight into an outlet in a different room and for some reason the hum got like 10x louder. Tried it back in the dedicated outlet for the rack and it cleared up completely. Wonder what was up with that other circuit and if it's related at all to to my problem.

Well, yes. But when you connected to power in the other room, was ANYTHING else in the system connected to power? From what you've described so far, you have a projector and a system in one room with no leads running to any other room at all; it's important to know about that. This latest hum source seems to be interaction between the ground in that other room and some other ground the equipment is connected to... but you haven't actually described all the wiring.
On December 11, 2014 at 08:25, thecapnredfish said...
Could you explain how these are improperly grounded.

The cable system goes all over the county, and for it to work properly it must be grounded at multiple points, the nearest one to you being at the cable demarc on your property.

Let's say the cable system is grounded at the pole, but at the pole there's a heavy imbalance of power being drawn by a couple of other houses. The nearest power transformer is grounded; the cable is grounded at the same location; but because of the neutral current due to the imbalanced load of other people, that ground is actually several volts above ground. Then the cable comes to your house and is not connected to a ground at your house. The shield then has several volts of AC on it, which are injected into your system when you connect the cable.

Even if you don't understand this, when troubleshooting hum the FIRST thing you should do is disconnect ALL cable feeds, satellite feeds, antenna feeds... as these may or may not have grounds and you won't know.
A good answer is easier with a clear question giving the make and model of everything.
"The biggest problem in communication is the illusion that it has taken place." -- G. “Bernie” Shaw
Post 12 made on Thursday December 11, 2014 at 11:36
sofa_king_CI
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Have you tried Fedex instead ;)
do wino hue?
Post 13 made on Thursday December 11, 2014 at 12:08
King of typos
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Then there are cable company guys who run the cable on the opposite side of the house that the power comes in. The electrician for the power grounded it right at the service entry for the power company. The cable guy grounds the cable at the nearest water pipe, example base board heat.

By law, this isn't legal at least that's what I was told in school. Due to the imbalance of the grounding spots. Granted, the hot water pipe is grounded at the same spot as the electrical service. However, how many solder joints has it gone through? 3, 4, 10 or more?

KOT
Post 14 made on Thursday December 11, 2014 at 13:03
buzz
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In one house I found the cable "ground" connected to an isolated one foot section of copper water pipe. I guess someone followed the directions literally -- "Connect ground terminal to copper water pipe."
Post 15 made on Thursday December 11, 2014 at 16:46
Ernie Gilman
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a person who actually goes by "buzz" should not be allowed to comment on this topic
A good answer is easier with a clear question giving the make and model of everything.
"The biggest problem in communication is the illusion that it has taken place." -- G. “Bernie” Shaw
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