Need help w/ Grotto Sub.....Hum Problem?

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Matt00

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Hi everyone,

I am new to the site...Anyway I recently purchased a grotto sub and I am very happy with it, it's a very musical and tight sub. I have it hooked-up with a krell 400xi inter amp and both are pluged directly into the wall outlet.

I have had the sub for 1 1/2 months and last night I started to get a humming sound from the sub? What is this from? What can I do to stop it? Please help.

Thanks,
Matt:bowdown:
 

Pcar928fan

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I have had the sub for 1 1/2 months and last night I started to get a humming sound from the sub? What is this from? What can I do to stop it? Please help.
Most commonly subs hum because of a ground loop. Did you just change something like an antenna connection to your Satellite or cable TV hook up? Those are the most common problems. Have you added or subtracted any other gear?
 

Matt00

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I didn't change anything, no gear or made any other connections! Thats why I don't understand it would happen now. I never had a problem before? Whould a surge/filter protector help?
 

Matt00

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Thanks for the info, but why would this happen a couple of months later. I never had the humming problem before?
 

jjay

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I had a similar problem with the first Grotto subwoofer I owned. It would come and go at times and get louder also. They let me exchange it with a new Grotto and not one problem in a year. If you purchased this new, make the dealer fix it or give you a new Grotto.
Jim
 

Craig

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It often comes in through your tv cable since the cable companies use a different grounding system. Do you have a TV cable plugged anywhere into your system? If so, disconnect it and see if the hum goes away. If it does then at least you know where it's coming from. If not you can disconnect each component from the system one at a time to track down the culprit.

Whatever the source of the hum, the best solution is to use a device like JonFo suggested.

I don't know why but subs always seem to bring out any ground loop hum that occurs in a system. Must be the 60hz frequency from the 110v/60hz electrical circuit. If you were in Japan it would then be a 50hz hum.
 

Pcar928fan

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I didn't change anything, no gear or made any other connections! Thats why I don't understand it would happen now. I never had a problem before? Whould a surge/filter protector help?
I actually unhooked one of the coax cables on my DirecTV sat. system at one point and that set my sub to humming! It was crazy. It was not even a coax cable that was connected to the system that had the sub in it!
 

Matt00

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Now it stopped!!

All of a sudden the hum stopped! It no longer makes any noise. Does this mean the sub may have a problem and needs to be sent to ML for repair?confused:

Thanks,
everyone for your imput.:
 

jjay

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My Grotto hum problem was a intermittent problem. I hope that it is solved but if this continues return the subwoofer to the dealer for an exchange.
 
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Craig

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I actually unhooked one of the coax cables on my DirecTV sat. system at one point and that set my sub to humming! It was crazy. It was not even a coax cable that was connected to the system that had the sub in it!
Reverse Ground Loop perhaps? If there is such a thing. I would suspect that your tv cable was actually providing a beneficial grounding source. I'm only speculating since I'm not a qualified electrician.

All of a sudden the hum stopped! It no longer makes any noise. Does this mean the sub may have a problem and needs to be sent to ML for repair?confused:
Ground loop hum is a wierd science to a mere layman like myself. The reason it's so common in HT systems is because they usually have a tv cable plugged into the system. Cable companies use a different type of grounding system then the home circuit uses. Maybe someone more technically skilled on this forum can explain this better than I. A subs internal amp and low freq capabilities will emphasize the hum.

Ground loop is such a common cause of hum in subs and HT systems that you really want to find out if it's ground loop or not before you go through all the trouble, time and risk of packing up your sub and shipping it to ML.

Another simple test is to spend $3 on a cheater plug (a power cord adapter without the ground pin available at the local hardware store). Use the cheater plug on your subs power cord and see if the hum goes away. If it does then you have a ground loop causing the hum. If that is the case then you'll need the part that JonFo mentioned. I don't recommend using the cheater plug long term. I you still have the hum with the cheater plug then I would suspect a defective sub.

This is a frequently discussed topic so you may want to do a search on it here and on other forums for more info.
 
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bob1957

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I installed a new amp in my system last night and experienced a ground loop for the first time. I went through all the normal diagnostic techniques, including the cheater plug, which confirmed that it was a ground loop.

It turned out that the coax connection from my cable box to my processor was the culprit, even though this had never been a problem in the year and half I've had this processor (four years for the cable box.) Weird. In any event, I replaced the coax with a toslink cable. It sounds fine and the hum is gone.

Bob R.
 

Pcar928fan

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It turned out that the coax connection from my cable box to my processor was the culprit, even though this had never been a problem in the year and half I've had this processor (four years for the cable box.) Weird. In any event, I replaced the coax with a toslink cable. It sounds fine and the hum is gone.
Seems the video section of our systems are the common cause of 95% of ground loop hums! That is the first and best place to look always!
 
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