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Discussion Starter #1
Hi guys,


I've bought a used Sunfire True Subwoofer Signature, cause I desperately wanted a small sized sub. It sounds great to me, however I have one problem: Even if I pull out all connections (except the power cable, of course), the sub is still audible from one of the two drivers. It's a deep bass sound, not very loud, but it's getting on my nerves. When I turn the volume control up, the buzzing gets louder. When I turn it all down, the buzzing is still audible, but less loud. After those 15 minutes when the sub switches to standby mode, everything is finally completely silent. The sub is running through a Monster line cleaner.


Any suggestions? Is it normal for a sub to behave this way? My old sub didn't do this. It was much bigger, though, and didn't sound as good.
 

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Sounds like a ground loop, my Sunfire does the same thing. Just get one of those cheater 3 into 2 plugs for use on unground outlets. I'm sure someone will chime in and tell you how bad this is and that it could shock you etc. but I haven't had any issues for over 6 years.
 

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Discussion Starter #3
Thanks for your comment. So with this cheat your Sunfire is dead silent, even if you turn volume full up?
 

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Does your Sunfire even use a three prong plug? I thought mine was only two prong, but I could be wrong (my entertainment center is too much of a PITA to pull out and confirm). And I have the original Sunfire, so things could have changed. In fact, I WANT to say that the plug on mine isn't even polarized, because I thouth that I remember discovering that I had hum with it plugged in one way, but reversing the the plug (effectively swapping neutral & hot) removed the hum. The hum did return when I got a BFD, which DOES have a three prong plug, but putting a cheater plug on it rectified that.


So if you DON'T have a grounded plug, try adding the cheater to it, but if it's two prong, try reversing it. You could also try a cheater on any other components you may have that are grounded. But it definitely sounds like ground loop, which results from multiple paths to ground. If those paths are required, the "proper" way to deal with it is with filters put in the audio cable that remove it. Personally, I'm perfectly comfortable with cheater plugs.


EDIT: I just realized that you say you get hum even with the audio cables disconnected. If that's the case, then I think your only option of easily fixing it is IF yours is like I remember mine being, and it has an un-polarized two prong plug. Reversing the plug may fix it. If that's not the case, then something may not be right with the sub. Without any other connections, there shouldln't be a ground loop. I'd have it checked out in that case.
 

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Discussion Starter #5
My Sunfire has a 3 prong plug. I already tried to reverse it, honestly I'm not totally sure how much that helped. I had a situation where there was a quite loud hum and another situation where there was "only" a lighter hum. So reversing the plug might have helped a bit.


However, yes, the sub still hums even with no audio cable connected (well, I pulled the audio cable on the receiver side, so that I can activate the sub by touching the lose end of the cable).

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If that's not the case, then something may not be right with the sub. Without any other connections, there shouldln't be a ground loop. I'd have it checked out in that case.
Does that mean that your sub is perfectly silent (when your receiver is off), even if you turn the subwoofer volume up to max? So if you put your ear next to the sub's drivers you don't hear *anything*? I need to get that straight.


Thanks very much for your help!
 

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Quote:
Originally Posted by madshi
Does that mean that your sub is perfectly silent (when your receiver is off), even if you turn the subwoofer volume up to max? So if you put your ear next to the sub's drivers you don't hear *anything*? I need to get that straight.
Yes, not only is my sub perfectly silent when my receiver is off, it eventually turns off due to lack of a signal. Yours shouldn't even be on, much less making noise. The power light (at least on mine) has two levels of brightness: dim when the sub is off, and brighter when the sub is on. If you disconnect the audio cable, making it impossible for it to get an audio signal, and it remains on past 20 minutes or whatever the timeout is, something is wrong.
 
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