Same Hum....different house....please help with SVS PB12-NSD hum - AVS Forum
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post #1 of 21 Old 01-13-2013, 09:28 AM - Thread Starter
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The problem: the sub hums as soon as a cable or satellite box is connected with the system. Pull the HDMI out of the cable/sat box, and everything is fine.

So we tried everything to get rid of the hum in the first house...pretty much everything that comes up in Google under subwoofer hum...and nothing worked. Had the power company out....cable company....independent electrician...spent months on it, and nada.

So now we hauled this beast to a whole new home (80 miles away), and hooked it up to a completely different system. We did not re-use a single cable, not even the sub power cord.

The result: identical hum.

And once again, it goes away as soon as we unplug the TV source. First was cable, second home is on satellite.

Any ideas? I'm at my wit's end....

Thanks!

PS - one symptom - the hum changes pitch quite a bit when you toggle the crossover switch on the back (regardless of Hz setting)...not sure if that's relevant.

edit - also, this sub came with a 2 prong cord...shouldn't a sub have a grounding plug?

...just my $.02 - GST included.
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post #2 of 21 Old 01-13-2013, 10:59 AM
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Check out this recent thread. Mine is the second last post there.

http://www.avsforum.com/t/1366597/sub-woofer-hum-another-one

Hums are often caused by mismatched grounding between cable or sat system providers' gear & the house power supply. I surmise that was my problem also.

TAM.
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post #3 of 21 Old 01-13-2013, 11:38 AM
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One way to eliminate all this is to instal an Isolation Transformer for your System. I installed a 5kv Iso Xfmer to power my entire theater.
This in essence is a separate power source from the power company. And after the instal there is no need for any type
of power conditioner. The power out of the iso is clean as can be. I use to have a brown out every time my air conditioner or dish washer would turn on. My PJ would dim etc. Also there was a hum I could not get rid of.

One thing tho there was still a slight hum and disconnecting my Sat cable would stop it. WHat I had to do was run the ground for the sat splitter box to the ground on the output side of the Iso Xfrmer. Before it was right into my Main panel box, no its on my Sub panel box after the Iso.

This works really well. I would however try to have the Iso in a separate room as Mine does have a mechanical hum.

Athanasios
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post #4 of 21 Old 01-13-2013, 11:56 AM
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Quote:
Originally Posted by Quill View Post

The problem: the sub hums as soon as a cable or satellite box is connected with the system. Pull the HDMI out of the cable/sat box, and everything is fine.
Transformer isolate the cable. Problem solved. This one is cheap, and works with most systems:
http://reviews.parts-express.com/2444-en_us/180-075/dayton-audio-vit-1-isolation-transformer-reviews/reviews.htm

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post #5 of 21 Old 01-13-2013, 12:03 PM
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Transformer took care of my problems here as well.
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post #6 of 21 Old 01-13-2013, 12:12 PM
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Quote:
Originally Posted by Bill Fitzmaurice View Post

Transformer isolate the cable. Problem solved. This one is cheap, and works with most systems:
http://reviews.parts-express.com/2444-en_us/180-075/dayton-audio-vit-1-isolation-transformer-reviews/reviews.htm

Those work but mess up high bandwidth info. I lost many HD channels with one of those.It even says so in the description its band aid and not a real fix.

Athanasios
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post #7 of 21 Old 01-13-2013, 12:22 PM
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Those work but mess up high bandwidth info. I lost many HD channels with one of those.It even says so in the description its band aid and not a real fix.

Athanasios
If that happens you buy one made to work with HD. They cost more, but still a lot less than some of the more exotic recommendations that don't address the simple issue of a ground loop. An even easier fix that usually works and is free is to remove the cable connector, trim back the cable shield so that it won't make contact, reattach the connector and hook it back up.

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post #8 of 21 Old 01-13-2013, 01:46 PM
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Never heard one peep from my PB12 NSD or my SB12 NSD. I had a Sunfire true signature sub that would hum off and on and drive me nuts.

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post #9 of 21 Old 01-13-2013, 07:55 PM - Thread Starter
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Originally Posted by CHASLS2 View Post

Never heard one peep from my PB12 NSD or my SB12 NSD. I had a Sunfire true signature sub that would hum off and on and drive me nuts.

...exactly...which makes this so frustrating. I'm guessing this Sub would hum anywhere, but SVS has basically said it's not their problem, since it works fine with no cable box attached.

...just my $.02 - GST included.
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post #10 of 21 Old 01-13-2013, 09:26 PM
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Quote:
Originally Posted by Quill View Post

...exactly...which makes this so frustrating. I'm guessing this Sub would hum anywhere, but SVS has basically said it's not their problem, since it works fine with no cable box attached.

If the sub hums with no cable attached I would have to agree with SVS.

Make sure the Sub and AV equipment are connected to the same Circuit. Also are there any dimmers connected tot he same Circuit?

Athanasios
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post #11 of 21 Old 01-14-2013, 06:07 AM
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Quote:
Originally Posted by Quill View Post

...exactly...which makes this so frustrating. I'm guessing this Sub would hum anywhere, but SVS has basically said it's not their problem, since it works fine with no cable box attached.
They're right. The fault is with the cable, not the sub. I've already made suggestions how to fix it.

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post #12 of 21 Old 01-14-2013, 09:41 AM
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Did you experiment with my solution? Try a temporary wire connection between the outer barrel of an unused RCA Jack on the sub to the outer barrel on one on the TV. See if there is any difference in hum.

Really easy in most setups if the rear of your components are readily accessible...

TAM
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post #13 of 21 Old 01-15-2013, 09:17 PM - Thread Starter
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Originally Posted by ex-labdriver View Post

Did you experiment with my solution? Try a temporary wire connection between the outer barrel of an unused RCA Jack on the sub to the outer barrel on one on the TV. See if there is any difference in hum.

Really easy in most setups if the rear of your components are readily accessible...

TAM

The sub is at a friend's place....and he's not technical enough to try the fixes rolleyes.gif. I'll be out on the weekend, and give them a shot! Thanks for the input--I'll post back with the outcome.

Cheers,

Quill

...just my $.02 - GST included.
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post #14 of 21 Old 01-15-2013, 10:29 PM
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I recently posted the below explanation for a customer on my forum. As I explain below, this won't always solve the problem, but it is a preferred means to solve the problem that doesn't involve cheater plugs. The summary is that you can either ground the receiver/preamp to the system ground through a Phono input ground screw or by connecting an F-connector type coax cable from the output of a surge protector with a cable/sat connection to the antenna input. The antenna/coax ground connection should be available to try for most, and such surge protectors can be had rather cheap. For those with a rack style surge protector they often have a brass/gold ground lug on the back which can be connected to the phono ground.
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Fortunately this should be a straight-forward fix. The issue typically boils down to various components having a connection to the 3rd pin safety ground in your home's wiring and those which don't. There are some other quirks and possible pitfalls, but this is the most common offense.

I'm working on a sticky note to post on our forum about two simple fixes I've come across. Most of these problems stem from the Onkyo, Integra, Denon, Marantz, etc. of the world using 2 prong power plugs for their devices. It is perfectly legal and to code through a few extra efforts (ie double insulated power transformers), while making it much easier for them to ship the same/similar unit all over the world with the fewest modifications. This practice means there is no use of the 3rd pin safety ground, where the "ground" or reference of the device is basically floating. This functions fine until you connect to a device with a different ground reference.

The preferred solution is to provide a ground connection to the floating devices rather than start floating the rest of the system leaving it open for more issues if a different ground connection is made in the system. On the back of these preamps you will find one or two simple connection options. Some still have a phono input for a turntable, and next to the RCA connectors is a thumb screw labeled "ground" or similar. Most rack mounted surge protectors or power conditioners have a brass ground lug on the back which you can connect to the phono ground with any small speaker wire or similar. The second easy connection point is the shell of the FM Antenna connector (coaxial F-type). Most all of the surge protectors I've checked thus far which have coaxial (cable/sat) protection have the shell of the connectors grounded to the 3rd pin ground at your wall. Simply take any cheap coaxial cable and connect the FM antenna to one of the outputs on the surge protector. This makes for two easy and clean means to establish a ground connection and confirm if this solved the problem.

I've helped a few customers recently with these two fixes and can credit one fellow SubMersive HP owner for helping me think of the antenna/coax connection option after the surge protector he purchased didn't have a ground lug. Note this also explains why we occasionally hear of those with problems buying a comprehensive surge protector, connecting everything through it, and their ground loop going away, even if the coax connection isn't being grounded directly to the preamp, the components still get grounded. It is also possible to ground the chassis of a preamp by loosening a screw on the back and pinching a wire under it which is connected to a power system ground. The trick there is to remember that the black finish on the metal is an insulator, so just touching the preamp's metal case won't work.

Hope that helps.

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post #15 of 21 Old 04-06-2013, 11:56 AM - Thread Starter
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Thanks for all the suggestions. I tried them all (in one more home as well), but none work.

The hum gets a tiny bit quieter as I touch connections to the surge protector's F-style connectors, but that means the hum goes from unbearable to very annoying....that's the best I could do.

I believe this is a design defect or flaw in the SVS subwoofer. How else do you explain why it doesn't work (if TV or SAT source is connected) in any of the three homes?

Not sure what to do from here...in the off chance anyone from SVS is reading, suggestions would be appreciated.

Otherwise I guess this particular SVS subwoofer hits the curb on "large item" garbage day...

Quill

...just my $.02 - GST included.
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post #16 of 21 Old 04-06-2013, 12:12 PM
 
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Quote:
Originally Posted by Quill View Post

So now we hauled this beast to a whole new home (80
miles away), and hooked it up to a completely different system. We did not re-use a single cable, not even the sub power cord.

The result: identical hum.

I hate it when hums follow me.

Quote:
And once again, it goes away as soon as we unplug the TV source. First was cable, second home is on satellite.

Any ideas? I'm at my wit's end....

An isolator.

I have and use two different isolators. One did a bang up job that I feel comfortable referring.



I used this isolator with no success.



It's a well reviewed isolator but I can't recommend it as in our case, my expected results were not met. That doesn't not mean the isolator didn't work, it's just means the isolator didn't correct our particular ground loop problem but the much more expensive box did as the actual offending cables, themselves, were isolated.

Quote:
edit - also, this sub came with a 2 prong cord...shouldn't a sub have a grounding plug?

It's a bit of a foreign concept but now equipment is being made with the neutral return being the ground as that's what a neutral return is. Hence why the plug is polarized. If there's a short, the extra amperage and potential gets shunted over to the neutral return. Even as a general contractor it took a while for me to get use to the idea of a neutral return being used as a ground.

Have you tried disconnecting the subwoofer cable? Pretty much, even if connected by a common metal shelf or pole stand, any attached appliance can introduce it's own ground loop problem. If when disconnecting the subwoofer "in," the hum goes away, then you need to put an isolator between the subwoofer cable and the subwoofer's "in" connection.

If you can, use a multimeter and when no signal is being sent to the subwoofer by the AVR (AVR turned on), measure the output of the subwoofer cable. The signal should measure zero to almost zero. Done in the fashion I recommend, the isolator in place, both supply lines measure 0.1mV.

-
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post #17 of 21 Old 04-14-2013, 12:01 AM - Thread Starter
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I hadn't seen the DTI isolator before...just tried an in-line one like the one pictured. I ordered it...here's hoping!

Thanks!

...just my $.02 - GST included.
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post #18 of 21 Old 04-14-2013, 05:20 AM
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I had a True Signature sub that would hum. Never heard a peep from both of my SVS subs.

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post #19 of 21 Old 04-14-2013, 05:42 AM
 
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Were they plugged into the same outlets and had you added any gear to the system?

Just saying, pretty much, any change can create or remove a ground loop condition.
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post #20 of 21 Old 04-14-2013, 06:30 PM - Thread Starter
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We unplugged devices one by one, and the sat box is the key.... Sub plus sat box (or cable box) equals hum.....

...just my $.02 - GST included.
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post #21 of 21 Old 04-14-2013, 07:01 PM
 
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Quote:
Originally Posted by Quill View Post

We unplugged devices one by one, and the sat box is the key.... Sub plus sat box (or cable box) equals hum.....

...biggrin.gif

Happy to read you were able to find the culprit. You just need to figure out a way to isolate the culprit from the system. Satellite systems, like cable systems, are notorious for their creative grounding solutions; they just grab anything readily available as that's what the direction expect.

Now that you know where the culpability lies, you should easily be able to acquire a viable solution such as what was linked to above.

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