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#89216 - 01/26/12 08:23 PM LFM-1 EX Hum
Ray916 Offline
Deputy Gunslinger

Registered: 01/26/12
Posts: 1
Hopefully someone can help me here.
I got my LFM-1 EX today.I powered it on and turned the volume to max, there is a humming sound with only one end of the subwoofer connected. I didn't connect the other end to receiver. If I turn the knob down, I don't hear the humming sound. When I switch it to X-over active I don't hear the hum.
When I connect the other end to receiver, only on the highest volume I get nice bass from the subwoofer.

Can some one help me please.

Thanks,
Ray.

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#89217 - 01/26/12 09:52 PM Re: LFM-1 EX Hum [Re: Ray916]
XenonMan Offline
Desperado

Registered: 04/08/08
Posts: 2676
Loc: Columbus,North Carolina
Sounds like a ground loop hum. Try plugging it into another receptacle. Does it make the noise with the AVR off and the sub fully connected to the AVR with the volume way up? Make sure your sub input cable is not laying parallel to a power cable somewhere.
_________________________
Music system
Model 990/7500/Magnepan 1.6 QRs/Technics SL1200 MK2/Aperion S-12 Subwoofer/OWA3/Sony NS75H DVD
APC H15 Power Conditioner

TV System
Large Advent Loudspeakers/ Polk center/Monoprice surrounds/Panasonic Viera 42 inch/Onkyo HT-RC260/Sony BDP S590/Directv


Home Theater System
Onkyo PR-SC886/Outlaw 7125 Klipsch RF-82 L/R,RC-62 center, RB-35 SR/SL, BENQ HT1075, Outlaw LFM1-EX/OPPO BDP-83/Directv
Harmony ONE
Blue Jeans and Monoprice interconnects
APC H15 Power Conditioner

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#93842 - 01/06/14 01:15 PM Re: LFM-1 EX Hum [Re: Ray916]
Alumiu90 Offline
Deputy Gunslinger

Registered: 10/03/13
Posts: 6
Is it possible to have a ground loop when the LFM-1 EX cable does not contain a ground prong?

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#93843 - 01/06/14 06:50 PM Re: LFM-1 EX Hum [Re: Ray916]
XenonMan Offline
Desperado

Registered: 04/08/08
Posts: 2676
Loc: Columbus,North Carolina
Yes because it has no ground plug it is dependent on the system to be at the same ground across all components. Remember that the cold side of the 120 vac receptacle is tied to the house ground at the breaker box so even without a ground prong the component is still tied to the house ground.
_________________________
Music system
Model 990/7500/Magnepan 1.6 QRs/Technics SL1200 MK2/Aperion S-12 Subwoofer/OWA3/Sony NS75H DVD
APC H15 Power Conditioner

TV System
Large Advent Loudspeakers/ Polk center/Monoprice surrounds/Panasonic Viera 42 inch/Onkyo HT-RC260/Sony BDP S590/Directv


Home Theater System
Onkyo PR-SC886/Outlaw 7125 Klipsch RF-82 L/R,RC-62 center, RB-35 SR/SL, BENQ HT1075, Outlaw LFM1-EX/OPPO BDP-83/Directv
Harmony ONE
Blue Jeans and Monoprice interconnects
APC H15 Power Conditioner

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#93847 - 01/08/14 04:28 PM Re: LFM-1 EX Hum [Re: Ray916]
renov8r Offline
Desperado

Registered: 11/13/02
Posts: 336
Loc: Illinois
Here is a nice illustration of what happens inside one's electrical panel:



The important details are that the either phase of the hot side could be "seeing ground" across the neutral connection as the neutral from the electrical company meter / service entrance is attached to ground inside the panel.

The folks at Jensen Transformer (who make an OUTSTANDING range of products to electrically filter / isolate A/C power...) have a very thorough pdf that explains all the gory details on how hum gets into systems -- http://www.jensen-transformers.com/an/generic%20seminar.pdf

A simpler overview is also online-- http://www.epanorama.net/documents/groundloop/home_solving.html

These amateur radio guys also have a nice clear explain how to isolate the power if you want to go that route -- http://amfone.net/Amforum/index.php?topic=13605.0;wap2

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#93855 - 01/10/14 02:21 PM Re: LFM-1 EX Hum [Re: renov8r]
Outlaw Nancy Offline

Gunslinger

Registered: 02/11/13
Posts: 167
Thanks renov8r for posting the great info !

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#93863 - 01/12/14 11:34 AM Re: LFM-1 EX Hum [Re: Ray916]
Alumiu90 Offline
Deputy Gunslinger

Registered: 10/03/13
Posts: 6
So what is the fix or what is the process of elimination to determine if the hum is caused by a ground loop. I spent a lot of time researching subwoofers prior to purchase and very disappointed right now.

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#93864 - 01/12/14 01:23 PM Re: LFM-1 EX Hum [Re: Ray916]
Alumiu90 Offline
Deputy Gunslinger

Registered: 10/03/13
Posts: 6
I was finally able to check the amp by itself and the woofer by itself and still at a loss for what is causing the hum. Here are my findings:

With amp disconnected from woofer and powered up and volume turned to 10 the amp does not make any abnormal sound (LFE disconnected)
With amp disconnected from woofer and powered up and volume turned to 10 and LFE connected the amp does not make any abnormal sound.
With woofer directly wired as a front speaker it plays without any rattle or abnormal sound.

The problem appears to be a function of pairing the amp with the woofer.

I have sent additional notes to Outlaw, but not sure what is the root cause now.

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#93869 - 01/13/14 01:16 AM Re: LFM-1 EX Hum [Re: Ray916]
Owl's_Warder Offline
Desperado

Registered: 06/29/01
Posts: 894
Loc: Grants Pass, OR
Are you saying that the woofer wired with just the LFE line out or just the amp outputs it works fine, but if you connect both then that's when you get the hum?

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#93871 - 01/13/14 01:37 PM Re: LFM-1 EX Hum [Re: Alumiu90]
Outlaw Nancy Offline

Gunslinger

Registered: 02/11/13
Posts: 167
I understand that you have been communicating with our tech Jim. I am sure he will be able to help you with the resolution of this issue, however it does sound like an typical ground hum.

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