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How do I stop speaker hum?
#168355 05/17/07 02:04 PM
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I have recently set up my 7.1 axiom surround speakers and I have noticed that they produce a loud hum when I turn on the receiver. I have found the cause to be when I hook my coaxial cable up to my cable box the hum starts. When I un hook the coaxial cable the hum stops. Any ideas?

Re: How do I stop speaker hum?
blondespot11 #168356 05/17/07 02:25 PM
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Quote:

How do I stop speaker hum?




Lyrics.com

Am I at all helpful??


OK, I don't have the answers for you, but it's a grounding issue...others here have dealt with it by using isolation transformers, I believe. They'll likely chime in with more...


::::::: No disrespect to Axiom, but my favorite woofer is my yellow lab :::::::
Re: How do I stop speaker hum?
blondespot11 #168357 05/17/07 02:32 PM
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Hi blondespot11,

First, good detective work on your part in isolating the source of the hum. You have a classic case of "ground-loop" hum,which is caused by a voltage differential between your incoming cable-box signal and the ground for the electrical system in your home.

You can get rid of it easily with one of these Axiom ground isolating transformers:

http://www.axiomaudio.com/groundisolator.html

Before you order it, you can try plugging your subwoofer and or your/AV receiver into a different electrical circuit than the one for your cable box--try a different AC plug across the room, if possible. That may do the trick. If the hum is still present, you'll need the isolating transformer, which, by the way, will pass all Hi-Definition digital cable signals (and analog video too) with no degradation. It has a bandwidth up to 1.5 Giga-Hertz. If you're interested, here's a detailed article I wrote on ground loop hum troubles and how to remove them:

http://www.axiomaudio.com/tips_eliminate_hum.html

Regards,


Alan Lofft,
Axiom Resident Expert (Retired)
Re: How do I stop speaker hum?
alan #168358 05/17/07 03:17 PM
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Thanks for the quick reply. I just got a call back from Jean Claude from the Axiom desk. He also pointed me to the isolator. I have tried plugging my subwoofer into another outlet with no luck so I went ahead and ordered the isolator. I will let you know what happens once I get it.

Re: How do I stop speaker hum?
blondespot11 #168359 05/22/07 03:36 PM
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Ok. I have received the ground isolator and it cut down the hum significantly, but I still notice a faint hum. When I unhook the cable to the subwoofer there is no hum at all. I have the EP350 v2. Are there some setting on my subwoofer that I should change?

Re: How do I stop speaker hum?
blondespot11 #168360 05/22/07 03:48 PM
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1. Does this isolator that you bought require a ground connection? If so, did you ground it?

2. Does the hum go away when you turn off your amp?

3. Try turning off all the lights and see if your hum goes away. If it does, your sub cable is picking up radiated noise from your lights. You could then try a cable that is more heavily shielded.

Re: How do I stop speaker hum?
Mojo #168361 05/22/07 05:37 PM
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does the 350 have the ground screw on the back of the amp chassis like the 500/600 do? If so it is something Axiom has advised you can try (removing the single screw). Check your 350 manual for mention of it, or someone else here can confirm.

Good luck.


-Dave

M80s VP150 QS8s EP500s
ravenmanor.com/cinema/
Re: How do I stop speaker hum?
dllewel #168362 05/22/07 10:02 PM
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I was thinking the same thing Dave. However, if you check the product page for the 350, the picture of the back does not appear to have a ground screw.

Also, to the poster, what type of cable are you using to the sub?


M80s VP180 4xM22ow 4xM3ic EP600 2xEP350
AnthemAVM60 Outlaw7700 EmoA500 Epson5040UB FluanceRT85


Re: How do I stop speaker hum?
SirQuack #168363 05/23/07 01:52 AM
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I went thru the same thing, except I solved it in reverse order. Chassis ground on sub first, then the axiom isolator. All the hum is gone, but on weak cable signals I get weird lines in the JVC with every bass hit. Not a problem on HD feed from the cable or DVD (optical), but strange still. I've got the power lines separated from signal lines as best as possible, and using XLR cables from the pre-pro. I'll eventually get it cleaned up... but at least it doesn't hum.

Scott


Scott

My HT
Re: How do I stop speaker hum?
a401classic #168364 05/24/07 12:59 PM
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You are correct, there is no screw to remove on the back of the 350. I ended up just going to Radio shack and getting a ground isolator RCA cable. I hooked that up to my subwoofer. I am now happy to say that I am hum free. Thanks to all who replied.

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