Question about Jensen JHT525 System

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Subwoofer hum My subwoofer hums even when I disconnect the cables leading from my other auto equipment. THe subwoofer continues to hum even though there nothing is attached - is is simply plugged into the ac outlet. Can you suggest what might be the problem?

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  • Stevieboy777 May 18, 2009

    Same problem, no RCA's plugged in - just the sub. I took it back today to get a new one as it was a week old and guess what?



    ...it's the same.



    I've been told it is the ground being shared with my amp - I should get a groundloop isolator???

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  • Master
  • 6,966 Answers

Hi,

Based on your description, the internal power supply of the subwoofer amplifier would be suspect. Often it would be a blistered or leaking filter capacitor. It is a relatively easy/inexpensive repair.

Hope this be of initial help/idea. Pls post back how things turned up or should you need additional information. Good luck and kind regards. Thank you for using FixYa.

Posted on Nov 10, 2008

  • frontline5 Jun 04, 2011

    I think I have the same problem, how do you go about fixing it?

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The issue a floating ground that causes the hum you are talking about. What are you connecting it to that causes the hum?

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I have atomic A-8 subwoofer and philips FR740 receiver. when i turn the amplifier and the subwoofer "on", the subwoofer starts to hum loudly and it is wery annoying. i made all the connections...


The symptom sounds like an open signal shield somewhere and the cable is acting like an antenna for airborne electrical noise.

Disconnect the RCA cable at the sub. Is it still humming? NO? Problem is external to it. YES? Internal. Broken ground somewhere.

Recheck all connections making sure to twist the RCA head as you install it so oxides will be worn off.

Consider what may have changed in the environment regarding electrical devices, motors, magnetic sources. Ensure signal and speaker wires as ar not running are as non-parallel to any power cords as practicable.

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Have an older (6 + Yrs) VX-10A model, that's worked fine up until now. I recently moved, hooked up the same stereo and surround sound speakers, which worked fine, but the subwoofer made a loud hum as...


Disconnect the input and see if it hums in the absence of an audio source. A bad audio cable shield or unwisely-routed audio cables will allow entrance of unwanted signals from external power sources, magnetic fields, even dimmer-controlled track lights. Sometimes, simply reversing the orientation of the ac power plug can eliminate humming.

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I have a yamaha yst sw320 subwoofer connected to a yamaha dsp-a595a amp. I recently disconnected my equipment and when i reconnected it im getting a feedback hum/noise through the sub. I've tried...


Subs don't go to a variety of connections on the amp. Let's stop guessing and stick with the prescribed one.

Register and download the manuals for free at retrevo.com

http://www.retrevo.com/support/Yamaha-YST-SW320-Subwoofers-manual/id/320bh340/t/2/

See page E1 regarding placement and safety.

http://www.retrevo.com/support/Yamaha-DSP-A595-Amps-manual/id/319ag821/t/2/

Page 44 - read about "humming".

If you have hum on the sub, is it there with and/or without the input cable attached?

Disconnect the input(s) and see if it hums in the absence of an audio source. A bad audio cable shield or unwisely-routed audio cables will allow entrance of unwanted signals from external power sources, magnetic fields, even dimmer-controlled track lights. Sometimes, simply reversing the orientation of the ac power plug can eliminate humming.

Mar 02, 2011 | Yamaha YST-SW320 Subwoofer

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I hear a humming noise from my Sunfire subwoofer - occassionally. I bought a kit from Radio Shack that supposed to cut down on noise from the electric outlet - it didn't work. Please help!


How to isolate annoying background hum.

As long as the music or movie is playing, you can forget about it, at least until a quiet passage occurs, then there it is again: HUMMMMMMM! Be gone, bad hum, you think. But, like a bad odor at the back of the fridge, it takes some dogged persistence to track it down and eliminate it.

Hum is a constant low-frequency buzz, usually at about 60 Hz or 120 Hz, which results from voltage differences between true "ground" (what you'd get shoving a copper pipe into the ground) and the electrical "ground" of your receiver's chassis, the incoming cable-TV feed, or any video or audio components interconnected within your system, including powered subwoofers. When this voltage differential exists, it's called a "ground loop," and the hum it produces is darned annoying. You'll hear the hum mainly from the subwoofer because it's a low-frequency noise, but there will also be hum from your floorstanding front speakers or even compact bookshelf models.

First, try disconnecting your subwoofer from the coaxial sub cable from your AV receiver but leave the subwoofer turned on. Does the hum go away? If it does, then the ground loop is entering the system from your AV receiver and/or your cable-TV system set-top box (or satellite dish and decoder).

Disconnect the incoming TV-cable or satellite feed to a set-top box or to your TV and the A/V receiver. If the hum disappears (and you don't use a satellite dish) complain to the cable-TV company. They may know what you need and supply you with a ground-isolating transformer. If they don't know what you are talking about you'll need to order a video ground isolator and install it in-line with the TV cable before it enters your set-top cable-TV box. Axiom has special wide-band isolation transformers that will not interfere with any digital TV or HDTV signal. (N.B. You CANNOT use one of these with a satellite decoder box.)

Before you order one, you can try plugging your subwoofer into a different AC outlet in the room, ideally one that is not on the same circuit as your AV receiver and video equipment (TV, DVD player, sat or cable TV box, etc.) That may solve the problem. If it doesn't, see if the back panel of your sub has a "ground-lift screw". It will be labeled as such. Just remove it. That may remove the hum. If it doesn't and you have a standard cable-TV feed (not a dish), then order the ground-isolation transformer. (Axiom has special wide-band isolation transformers that will not interfere with any digital TV or HDTV signal.)
Axiom Audio Ground Isolator

If that still doesn't eliminate the hum, or if you use a satellite dish video feed, then you could try one of these from Radio Shack, which goes between the subwoofer and the coaxial cable from the receiver's subwoofer output.

With persistence, all ground-loop problems can be solved.

Hope it helped..

Have a nice day...

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1 Answer

After a power outage I have a loud hum.


Hi, The Ground Rules Of all the annoyances that can afflict any audio/video home theater or even a simple stereo installation, the notorious "ground loop" may well be the most difficult and persistent one to track down and eliminate. A "ground loop" is caused by the difference in electrical potential at different grounding points in an audio/video system. (All the grounds in an A/V system should ideally be at "0" potential.) A ground loop typically adds a loud low-frequency hum or buzz as soon as you plug in any of various audio or video components, including subwoofers, cable-TV outboard boxes, satellite-TV feeds, TV displays, amplifiers, A/V receivers or turntables. The buzz/hum is a byproduct of the multiple power supply cables and a ground voltage differential within your system and its network of interconnecting cables.

Here are some methods to help you get rid of ground loops. Try these first and don't waste money on a power "conditioner" which, in most cases, won't help. (There is no need to "condition" the AC power for your system. Your receiver or amplifier already has a power supply with its own filters and transformers. No further filtering is normally required.)

If you get your system up and running and hear an audible buzz or hum, the first culprit to look at is either the powered subwoofer or your cable-TV or satellite-box feed at the entry point to your system.

First, the subwoofer: unplug the coaxial cable that connects to your powered subwoofer to see if the ground-loop hum disappears. If it does, it's likely coming in through your cable/satellite TV feed.

Reconnect your subwoofer's coaxial cable from the subwoofer input to your receiver's subwoofer output and disconnect the cable-TV feed (or satellite feed) from your outboard set-top cable box or satellite tuner. Be sure and disconnect the cable before any splitters. Now see if the hum/buzz from your subwoofer stops.

If that eliminates the hum, you can install one of these inexpensive in-line ground isolators from Parts Express or Bass Home. Note that these transformer-based ground isolators will work fine with analog cable-TV feeds, but depending on their design they may interfere with or block reception of HDTV signals via a digital cable or satellite dish feed.

Install the ground isolator between the cable-TV feed and the input of your outboard cable-TV box or satellite tuner (or the TV display's antenna or cable input if you have a set with a built-in TV tuner or a cable-card ready set). In many cases, the ground isolator will "break" the loop and remove the annoying hum or buzz by isolating the TV-cable ground.

If a hum remains with the TV cable completely disconnected from your system, or you don't want to risk degrading reception of HD signals from a cable or satellite system, then you may have to add a ground isolator like this Radio Shack Model 270-054 between the line-level coaxial subwoofer cable from your A/V receiver and the line-level input jack on your powered subwoofer.

In all cases, if your subwoofer has a ground-lift screw like some of Axiom's subwoofers, try first removing the screw (or replacing it) to see if it increases or eliminates the hum. It may or may not make a difference.

If you do not have easy access to the aforementioned ground isolators, here are a few more tips:

Try plugging the subwoofer into a different AC outlet in the room, one that isn't supplying power to your components (A/V receiver, TV, cable box, etc.). That might fix it.

Try reversing the AC plug for your A/V receiver or the powered subwoofer. If it's a 3-wire plug or a polarized plug, which has one prong wider than the other, you won't be able to reverse the plug. For safety, do not use a "cheater plug" to bypass the 3-wire plug.

With the power OFF, reverse the AC plugs one by one of any other components that have a standard 2-prong AC plug that isn't polarized. Each time you reverse a plug, turn on the system with the attached component and your subwoofer and see if the hum disappears. In some cases, reversing one or more plugs will eliminate the hum.

If you have a turntable, try connecting a separate ground wire to a chassis screw on your preamp or receiver and see if the hum disappears. If you already have a turntable ground wire, try removing it from the preamp. One or the other may eliminate the hum.

Finally, here is another solution that worked well for a member of our message boards who decided to discard his ground-loop isolator on his subwoofer: "I took off the ground-loop isolator I'd been using and connected a plain 14-gauge wire to chassis screws on the sub and the receiver then powered everything on. Although hum was still there, it was far lower than before. Next I unscrewed the ground-loop screw on the back of the sub and that took care of the hum completely."

Almost certainly sounds like an earth loop to me, but can be caused by a poorly made transformer or phase shifts on the mains supply. Visit some power conditioner web-sites like Isotek or Isol-8 (or google "earth loop") where there's plenty of advice on how to reduce/eliminate earth loops and other causes of mains-induced hum (transformer problems etc).

Hum on the speakers usually indicates that there is a DC voltage on the speaker line. DC voltage on the output lines would be caused by a shorted output transistor.


Have a nice day...

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1 Answer

Sunfire MK II Subwoofer hum. I have a Sunfire MK II subwoofer that hums when it is plugged in (it even hums when no signal is connected). I've tried multiple outlets on different circuits, but hum...


you have a ground loop issue you could purchase a ground loop isolator, jensen makes them for about 40 bucks.I have discovered that if you have cable tv, unplug the incoming cable in your cable box and see if hum disappears.

Nov 25, 2010 | Sunfire True Sub MK II Subwoofer

2 Answers

Humming sound in subwoofer after it's been playing for a while


It sounds like you are describing an earth loop problem. I won't go into detail in this post, but try an isolation test first. disconnect everything from the reciever except the sub and try connecting say a BATTERY powered mp3 player or cd player to minimise connections to the electrical mains earth. you could also isolate things by taking your sub to a friend's house and trying it on their system.
If it is an earth loop use a process of elimination to find out which two pieces of equipment causes the earth loop. then apply filtering.
you can buy earth loop isolation transformers for about AU$26 and I've used one on my sub myself. Theyhave RCA (phono)plugs on each end and they connect inline with the signal cable to the sub amp.

as for the thumping sound it might be the speaker protection circuitry cutting off the amp to protect the subwoofer speaker from damaged. This might be triggered if the earth loop sound is causing the sub amp to overload and clip.

Failing this there might be a dried out overheated electro capacitor in the amp circuit causing the hum. Hav a chat to your local electronics person, who should be able to spot it!
Hope this puts you on the right track
Happy Hunting!

Jan 07, 2010 | Sunfire Speakers & Subwoofers

1 Answer

Loud Hum in Pinnacle 150 subwoofer


The hum is likely due to either a failed capacitor in the subwoofer power supply or as it was for me, a cold solder joint on the capacitor. The fix is simple, but does require soldering. Unplug the subwoofer and set it on a good working surface. Remove the screws holding the back panel to the cabinet. These screws are the ones near the edge of the panel. Take off the panel by pulling back on it, reach into the subwoofer and carefully unplug the red and black speaker leads noting which one goes to each connector. Orient the panel with the electronics side up and the power cord at the lower right of the panel. Just to the left of where the power cord is soldered to the board is a large cylindrical capacitor. It is by far the largest cylidrical component on the board. This capacitor filters the hum made by the step down transformer in the power supply. If the capacitor is not working the subwoofer hums. The capacitor is soldered to the back of the electronics board. We had to reach in with a modified soldering iron to remove the capacitor. Before removing the capacitor check the orientation, there is a plus and minus, make sure it goes back in the same way. After removing the capacitor inspect the capacitor leads to see if they were both soldered correctly. If one of the leads is not silver the most likely cause is a cold solder and the fix is to simply clean up the capacitor leads by scraping off anything that is not silver, tinning the capacitor leads and re-soldering it to the board. If the leads look like they had a good solder, test the capacitor by using an ohm meter (used to test resistance) between the capacitor leads. The meter should show low resitance and as the capacitor charges the resitance should go up to infinite. If the meter does not behave this way while testing the capacitor, replace the capacitor. Bring the old capacitor with you to the electronics part store to make sure you get one that has the same electrical properties as the one you are replacing. The form of the capacitor might be different but as long as it is has the right electrical properties it will work. - and don't foget to make sure the polarity is correct when you solder it in!

Nov 06, 2007 | Pinnacle PS Sub 150 Subwoofer

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