Weird, weird subwoofer hum... - AVS Forum
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post #1 of 18 Old 07-07-2012, 11:42 AM - Thread Starter
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I have a crazy weird subwoofer hum issue. Currently using a 12 year old Sunfire true subwoofer connected to a Denon AVR-3311 (had the same issue with my old Sony STR-DA30ES). The subwoofer is always connected and on and makes no hum. When I use it with quiet music it also doesn't hum. But when I play loud music or movies it starts a very loud hum. What's weirder is that I can get it to stop humming by flipping various wall switches. But the kicker is its always a different switch. My family room has three different wall switches (some are 3 way control) and when the sub starts humming I flip each one on and off again until it turns off. If a switch stops the hum one time it most likely will not the next, but one of the others will. The sub is plugged into its own outlet that is not connected to a wall switch. One time it was humming and my wife flipped on a light 3 rooms away and the sub stopped humming.

I have tried plugging the sub into its own power strip and it made no difference. Does anyone have any thoughts?
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post #2 of 18 Old 07-07-2012, 03:23 PM
 
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Poor ground either on that circuit, or at the panel, going to earth ground. I would definitely check all outlets and light switches, that the wires are connected to the screws, not just pushed in the back as a "backstab", and also that all wires that are in either Wago's or wirenuts, tightened to secure the wires inside. Any loose connection anywhere, especially with grounds, will cause hum.
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post #3 of 18 Old 07-09-2012, 09:19 AM
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You can try a ground loop isolator.
http://www.parts-express.com/pe/showdetl.cfm?Partnumber=265-012

If in a hurry, you can get one at Radio Shack.
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post #4 of 18 Old 07-10-2012, 06:40 AM
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Poor ground either on that circuit, or at the panel, going to earth ground

Is the sub grounded?
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Any loose connection anywhere, especially with grounds, will cause hum.

No, not true at all.
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post #5 of 18 Old 07-10-2012, 11:41 AM
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I have a sub that hums. I've found it hums when plugged into some outlets and doesn't hum when plugged into others. I think the problem is with the sub as i've had the same issue with the sub in 2 different rooms. Maybe try pluggin it into a different outlet.
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post #6 of 18 Old 07-10-2012, 05:13 PM
 
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No, the problem would be due to wiring issues of the ground wire, or possible "bootleg" of the Neutral on the ground terminal. As I stated before, as long as the outlets are properly grounded, and all panels in the electrical system are properly bonded to earth ground, there should not be any issues with hum or ground loops.
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post #7 of 18 Old 07-11-2012, 05:38 AM
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No, the problem would be due to wiring issues of the ground wire,

If the sub isn't grounded, then this isn't the issue.
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or possible "bootleg" of the Neutral on the ground terminal.

Neutral and ground are bonded together.
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As I stated before, as long as the outlets are properly grounded, and all panels in the electrical system are properly bonded to earth ground, there should not be any issues with hum or ground loops.

You state a lot of things that aren't true, such as this. Ground loops can occur with ungrounded equipment, it happens all the time.
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post #8 of 18 Old 07-11-2012, 08:54 PM - Thread Starter
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I am going to try a ground loop isolator as well as whatever you call the 3 prong to 2 prong adapter to see if it helps. I have plugged into 3 outlets as well as wall / power conditions to no avail. What I find odd is how different switches stop the problem at different times...
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post #9 of 18 Old 07-17-2012, 09:51 AM - Thread Starter
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Well, yesterday I finally purchased a $.69 cheater plug from my local hardware store and no hum from the sub at all. Pissed at myself for dealing with this for years when the fix was less that a dollar...
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post #10 of 18 Old 07-17-2012, 06:20 PM
 
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Originally Posted by theanimala View Post

Well, yesterday I finally purchased a $.69 cheater plug from my local hardware store and no hum from the sub at all. Pissed at myself for dealing with this for years when the fix was less that a dollar...
No, the fix is not a dollar. The problem is still there, waiting for you to fix it.
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post #11 of 18 Old 07-17-2012, 08:03 PM
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My Sunfire sub had the same issue... This is a very common issue with Sunfire subs. Another issue is that the drivers fail when overdriven... The cheater plug will only last so long and the hum will reappear again. I sent it in to Carver Audio and they fixed it for $290+ shipping. They had to replace about a dozen caps and some varistors and diodes. They also had to reroute the ground from the amplifier chassis to the ground line on the AC cord.

The main hiccup is that the amp generates a lot of heat which shortens the life of the cheap caps used. Also, according to the tech, the sub amp is transformerless which means it is more susceptible to hum than other amp designs. They also mentioned that if people wait too long to fix it, some damage may happen on the amp board which will make it more expensive to repair.

If it's not a BIG screen, it's not a theater...
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post #12 of 18 Old 07-18-2012, 03:05 AM - Thread Starter
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Wow, $290 to fix a 12 year old sub? While I appreciate the small size of the sub I no longer have the same size restrictions so I will most likely just throw it away and put the repair money towards something else if it happens again.
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post #13 of 18 Old 07-18-2012, 07:48 AM
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My Sunfire MKII hummed too. I used the cheater plug. Fixed the problem as long as the amp lived, over 10 years. This is a common way of fixing hum in audio equipment. My Outlaw LFM-1 EX does not have a ground prong. I did pro sound for bands for 10 years and it was a common fix for my amps and mixer board to use cheater plugs, as it was for the guitar players in the band on their amps.

Animala, get you one of these Outlaws, it handily outperforms my Sunfire.
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post #14 of 18 Old 07-18-2012, 09:44 AM
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I did pro sound for bands for 10 years and it was a common fix for my amps and mixer board to use cheater plugs, as it was for the guitar players in the band on their amps.

Actually, it's not a fix...it is a good way to kill band members though.
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post #15 of 18 Old 07-18-2012, 12:41 PM
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It has been done this way for probably longer than I've been alive (45 years). No band member has ever experienced even the slightest shock around me, except for at one club where the wiring was wired out of polarity in some outlets, and even then it was only a slight shock easily corrected by running all the equip we could to outlets on the same circuit. Unfortunately that meant we popped the breaker a lot that night, but you do what you gotta do. Anyway, our guitar player and bass player have been doing it this way since the 70's, and you go back only a little farther than that and 3 prong grounded outlets were uncommon giving you no choice but to run only 2 prong plugs.

You are almost beginning to sound like a fear monger. There is plenty of equipment around that does not require 3 prongs. I haven't died from any of it, either.

The only thing the third prong does is protect the user in the event the normal neutral wire failed for some reason (cut, disconnected, etc.) You'll know this has happened pretty quickly when your gear stops working.
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post #16 of 18 Old 07-18-2012, 01:47 PM - Thread Starter
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Quote:
Originally Posted by TornadoTJ View Post

My Sunfire MKII hummed too. I used the cheater plug. Fixed the problem as long as the amp lived, over 10 years. This is a common way of fixing hum in audio equipment. My Outlaw LFM-1 EX does not have a ground prong. I did pro sound for bands for 10 years and it was a common fix for my amps and mixer board to use cheater plugs, as it was for the guitar players in the band on their amps.

Animala, get you one of these Outlaws, it handily outperforms my Sunfire.

Thanks, actually I did just upgrade to an Epik Empire and e output difference is noticeable. I still like the sunfire though and I'm thinking of turning it down and using it as a second sub in the same setup.
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post #17 of 18 Old 07-19-2012, 05:34 AM
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You are almost beginning to sound like a fear monger.

with my single post correcting your misconceptions?
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There is plenty of equipment around that does not require 3 prongs. I haven't died from any of it, either.

ANd you clearly have no idea what a safety ground is for or why there can be '2 prong' devices.
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The only thing the third prong does is protect the user in the event the normal neutral wire failed for some reason (cut, disconnected, etc.)

So sad....you have no idea.
Safety ground is there to protect people like you from electrocution from the hot wire. Neutral is at ground, so you can't get electrocuted from that. Safety ground is not there to take over from a failed neutral.


Good luck.
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post #18 of 18 Old 07-20-2012, 07:24 AM
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I have the same problem. I will look into trying to fix the "problem" at some point, but for now, the 'bandaid' (3-to-2 cheater) will do. My sub is backed into a corner, and weighs 125 lbs. If the amp fails and wreaks havoc, the circuit breaker will trip for the amp and/or room. The chances of someone touching the amp in an area to cause electrocution, while it is plugged in, and fails at the same time, are very small... But I do have to check the house grounding circuit and fix it.

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