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Hi again, I now have another issue with my subwoofer. i noticed a humming sound coming from it even when my denon4306 receiver is off. when i turn the receiver on the humming from sub is slightly louder. when i disconnect it from the receiver it goes away. i unpluged the power cord and tried another outlet and there was no difference. the only time it stops is when the rca patch cords are disconnected. my receiver is plugged into a monster surge protector and it seems to be working properly. we have been having power outages recently and i'm wondering could this have affected my receiver's subwoofer outlet. it's noticable but not too anoying yet. any idea what could be causing this humming from the sub.
how do i check the ground on both units. i hear this hum even when the receiver is unplugged. when i turn on the receiver it gets slightly louder. my sub is turned up about 3/4 of full volume. it gets lower as i turn the volume down. but as stated earlier when i disconnect the rca from the sub the hum disappears. the other speakers are connected to my amp and they seem to be fine. other than a scratching noise coming from the right channel in the first 5 minutes that i turm my system on. only the sub is connected directly to the receiver. i'm thinking it may be the receiver, but i have no way to check the ground. it's plugged into the monster line conditioner. thanks for reply, i appreciate your advice. money is low right now and i cant afford to get it serviced. so i'm looking for solutions myself.how do i check the ground on both units. i hear this hum even when the receiver is unplugged. when i turn on the receiver it gets slightly louder. my sub is turned up about 3/4 of full volume. it gets lower as i turn the volume down. but as stated earlier when i disconnect the rca from the sub the hum disappears. the other speakers are connected to my amp and they seem to be fine. other than a scratching noise coming from the right channel in the first 5 minutes that i turm my system on. only the sub is connected directly to the receiver. i'm thinking it may be the receiver, but i have no way to check the ground. it's plugged into the monster line conditioner. thanks for reply, i appreciate your advice. money is low right now and i cant afford to get it serviced. so i'm looking for solutions myself.
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Hum can come from a jillion different places. Is this hum coming from the unit with no speakers connected, or is it heard through the speakers? What sources are being used? What cables? Are thereany common sources of interference near? Troubleshooting is difficult without much information.
To answer your question;
From your description of the problem it sounds like your powered subwoofer has a power supply circuit problem.
It would be either with the large capacitors in the first stage of the supply(most likely) or with the regulation system that supplies +-15 volts to the preamp section.
If you are not familiar with electronic circuits you could still ask a repair shop to verify those large capacitors.
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.
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!
1-shut down all flourecent lamp and check. 2-check for your cables in a good condition and no touching of wires to the body of amp. 3-connect(ground loop isolator)code number(270-054)from radio shack near you and connect it between your audio device(like cd player and amp)
I had this issue a few years ago and the power cable from one of the inner terminals had come loose. It was still touching but whenever the sub would really pound it would jump off the connection and then reconnect causing it to hum. It was the most annoying thing ever so I finally pulled off the amp plate (super easy) and you could clearly see the loose wire. I had to use a good soldering iron to put it back on since it's a pretty fat wire. If you're not under warranty anymore then pop the back off and see if that's the issue.
The humming sound usually comes from the DC supply that is not filtered. The a/c converted or changed to DC needs to be "cleaned", before going into the ckt. Usually the capacitor and resistor network go bad, maybe causing the fuse to open. Even if you replace it, u may still have the "humming" because the circuit is still bad. If you know how to look at the capacitor, resistor,or coils AFTER the diodes & replace the damaged part, u should be good!
how do i check the ground on both units. i hear this hum even when the receiver is unplugged. when i turn on the receiver it gets slightly louder. my sub is turned up about 3/4 of full volume. it gets lower as i turn the volume down. but as stated earlier when i disconnect the rca from the sub the hum disappears. the other speakers are connected to my amp and they seem to be fine. other than a scratching noise coming from the right channel in the first 5 minutes that i turm my system on. only the sub is connected directly to the receiver. i'm thinking it may be the receiver, but i have no way to check the ground. it's plugged into the monster line conditioner. thanks for reply, i appreciate your advice. money is low right now and i cant afford to get it serviced. so i'm looking for solutions myself.
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