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PostPosted: Fri Jul 27, 2018 6:56 pm 
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Joined: Sun Jul 15, 2018 12:43 pm
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Location: Guelph, ON, CA
Hi this is my first post, as the subject states I have been having a problem with a hum in my system. I have a marantz 7702 mk2, two rotel rmb 1575's, two 15" subwoofers, and two rear subwoofers (12,3-10's) my speakers are 4 Polk rtia9's one rti 12 and two audiosphere research monitor 18l 7 speaker 3 ways. Everything is plugged into a panamax mr5100 except my 2 rear subs. Any help would be greatly appreciated, thanks. My best thoughts are it's a ground loop of some kind except it's only really on one or two channels. I am kinda thinking it may be a poorly shielded cable as my power cords and speaker wires and signal cables are in fairly close proximity in a few places. Thanks again


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PostPosted: Sat Jul 28, 2018 3:07 am 
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Joined: Sat Aug 25, 2007 2:00 am
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Location: Guelph, ON, CA
Tracking it down can be a long process. I think you will need to turn off and unplug some stuff before you start troubleshooting. Try it without all subs disconnected and unplugged. Use just one set of speakers. While you're troubleshooting, you may as well disconnect/unplug anything else that could generate noise into the remaining system (ie. cable TV if it's part of the system, modem/router if near your equipment, etc.) Do you still get hum in a simplified system like this?


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PostPosted: Sat Jul 28, 2018 3:54 am 
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Joined: Thu Jan 13, 2011 11:29 am
Posts: 779
Location: St.Catharines, ON, CA
Welcome.

What channels and what's associated with those channels?
Long line level cable feeding those channels?
Those channels(powered subs) on a different duplex outlet than the Panamax?

Make sure power cables aren't lying on top of line level cables.

Gary


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PostPosted: Sat Jul 28, 2018 4:51 am 
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Joined: Fri Jul 24, 2009 4:23 am
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Location: ottawa, ON, CA
your marantz is a home theater receiver so try disconnecting your tv cable input. if the hum stops then you need a ground breaking device on your cable input


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PostPosted: Sat Jul 28, 2018 9:28 am 
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Joined: Tue May 08, 2012 5:16 am
Posts: 98
Location: peterborough, ON, CA
I have the exact same problem but I have isolated the source. My hum stops when the amps are disconnected from the AVR. I'm using half decent blue jeans interconnects so I don't think they are the issue. No idea why the receiver (Pioneer Elite) and the amps (Bryson 3bst and 5bst) don't want to play nicely together, I even called Bryson and tried a few things with their service guy on the phone but nothing worked.
One thing I'm wondering about, the receiver has a 2 prong plug vs 3 prong on the amps, could this be the issue?
Unhook the interconnects from receiver to your amp then turn your amp on and see if you still have the hum.


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PostPosted: Sat Jul 28, 2018 10:14 am 
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Location: St.Catharines, ON, CA
The equipment is the victim.It's safety ground voltage differences that are the culprit.

G


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PostPosted: Sat Jul 28, 2018 10:36 am 
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Joined: Thu Aug 18, 2005 3:44 pm
Posts: 720
Location: Repentigny, QC, CA
Had an issue with hum coming from cable tv box, disconnecting coax or hdmi from the box isolated to the incoming coax from outside.
Ended up using the cable signal coax connected to a Monster Cable HTS 3500 in-out coax connectors to have all ground at the same potential.
now TV, radio, phono, is all clean no hum.


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PostPosted: Sat Jul 28, 2018 10:42 am 
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Joined: Sat Mar 25, 2017 5:35 pm
Posts: 5
Location: Waterloo, ON, CA
Dmamacd wrote:
Hi this is my first post, as the subject states I have been having a problem with a hum in my system. I have a marantz 7702 mk2, two rotel rmb 1575's, two 15" subwoofers, and two rear subwoofers (12,3-10's) my speakers are 4 Polk rtia9's one rti 12 and two audiosphere research monitor 18l 7 speaker 3 ways. Everything is plugged into a panamax mr5100 except my 2 rear subs. Any help would be greatly appreciated, thanks. My best thoughts are it's a ground loop of some kind except it's only really on one or two channels. I am kinda thinking it may be a poorly shielded cable as my power cords and speaker wires and signal cables are in fairly close proximity in a few places. Thanks again


1st off my very 1st amp was a Marantz ... loved it ... does yours come with an actual ground post on the back? I actually had to ground the amp as well as the turntable to get rid of any humming that came up. Best of luck

-- 28 Jul 2018 18:45 --

sasquatch wrote:
The equipment is the victim. It's safety ground voltage differences that are the culprit.

G


Great post ... good to know.


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PostPosted: Sun Jul 29, 2018 5:20 am 
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Joined: Tue May 08, 2012 5:16 am
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Location: peterborough, ON, CA
Later night I pulled out the 3 pronged bryston amp and put in a 2 pronged rotel amp, no more hum.


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PostPosted: Sun Jul 29, 2018 7:13 am 
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Location: Delta, BC, CA
Ah yes, everyone's favorite kick in the butt problem.....with all my cables and changes of components, I have also run into a number for ground loop/hum issues..... slow procedure, but the easiest way is to simply wiggle every single connection and unplug every connection, one by one...and plug it back in until you stop the noise, changing from a 3 prong to a 2 prong power cord is not a good idea, you are eliminating a safety feature the manufacturer put in for a reason.

Also every cable can be moved to see if the noise stops..... eliminate each unit in the path.... slow hateful procedure, but you will find the loop sooner or later...


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PostPosted: Sun Jul 29, 2018 9:27 am 
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Joined: Thu Mar 05, 2009 8:03 am
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Location: Scarborough, ON, CA
Make sure all equipment is plugged into the SAME power circuit as using different outlets will cause a ground loop. A simple fix that will also protect your equipment would be to buy a UPS and plug all your audio into it which will guarantee no ground loop.


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PostPosted: Sun Jul 29, 2018 9:55 am 
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Joined: Sun Jan 05, 2014 5:18 pm
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Location: etobicoke, ON, CA
Such a frustrating problem. The most likely scenario is that the grounds are mismatched between your various equipment.

The process is to pull each possible source until you know the culprit. For example, disconnect each sub from the system and turn it back on. If, after removing it, there is still a hum, you know it isn't the issue. It's a boring process.

Then, after you've identified the issue, you'll want to get your hands on a ground lift, or another power conditioner that can manage to get rid of it. Some ground lifts have proven to be more effective than others for me. You might have to try a few out.


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PostPosted: Sun Jul 29, 2018 10:00 am 
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Joined: Thu Jan 13, 2011 11:29 am
Posts: 779
Location: St.Catharines, ON, CA
Any two pieces of 3-prong gear interconnected with cable will form a ground loop.
Can be 1ft or 100ft loop. Obvious the shorter the better for hum/buzz.
UPS,power isolation transformers/conditioners won't eliminate ground loops as they are themselves 3-prong.
No isolating/conditioning of the safety ground.

Example below shows how very large loop can be shortened to very small just by moving a plug
from one branch duplex to the other branch.Lets say both branch circuits are 30ft from the panel.

G


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PostPosted: Sun Jul 29, 2018 12:17 pm 
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Joined: Tue May 08, 2012 5:16 am
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Location: peterborough, ON, CA
Tutone wrote:
Ah yes, everyone's favorite kick in the butt problem.....with all my cables and changes of components, I have also run into a number for ground loop/hum issues..... slow procedure, but the easiest way is to simply wiggle every single connection and unplug every connection, one by one...and plug it back in until you stop the noise, changing from a 3 prong to a 2 prong power cord is not a good idea, you are eliminating a safety feature the manufacturer put in for a reason.

Also every cable can be moved to see if the noise stops..... eliminate each unit in the path.... slow hateful procedure, but you will find the loop sooner or later...

Please note, I didn't change the cords, nor would I suggest that, I changed the amps. One amp uses a 3 prong plug, the other uses a 2 prong plug. Using the amp that came with the 2 prong plug as well as my AVR which also came with a 2 prong plug eliminated the hum.


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PostPosted: Sun Jul 29, 2018 12:29 pm 
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Joined: Mon Sep 16, 2013 12:20 pm
Posts: 423
Location: Delta, BC, CA
You are correct Mr. Willybilson.... changing amps is no issue...!!


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