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 continues. Shouldn't the internal power supply should filter out this hum.

Hi,
I had the same problem as this, the fix was quite simple and the hum never came back.

If you pull straight out on the sub amp's volume knob it will slide off, then to fix the hum, tighten the nut that is behind the knob on the potentiometer and your hum should go away. My hum went away and never came back after this fix. Hope this helps you.

use a ground loop isolator from radio shack, the device is hooked up to the rca plugs in, the other side has, (of course rca plugs), outs. solved My problem of feedback in the sub and into the processor.....

guy gevais

Check your cabling to make sure you dont have a ground fault. if you still have humming, buy a "groundless" adapter for your power plug (takes the ground away) and plug it back into the power outlet and I bet your humming will be gone

Iassume you mean you hear the buzz independently of the audio program - simply connecting the cable causes the buzz?

If tanything in the mix is powered from different AC sources you may have a different ground potential. Sometimes manipulating the orientation of one or more ac plugs will solve hum problems.

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!

Try plugging the unit into a clean power supply without anything else on it. I had this problem for years and eventually resolved it by moving the system to a different room that has three power circuits - the sub is now on it's own circuit and I don't have the problem anymore.

Some subwoofers can sense the signal on their input and will only start when there's enough signal for long enough time for them to turn on the amp.

Try seting the "subwoofer signal out" on your reciever a bit higher, see if it does the trick, if not, try it with some other source (e.g. an mp3 or CD/DVD player) plugged directly into the subwoofer. If it still doesn't work, there's some other problem with your sub (bad connection inside sub, sub amplifier problems, maybe there's another fuse for the speaker itself, try to check it out).

If it works well with an alternate signal source, the problem might be either in reciever or the signal cable that you use, but could also be something else.

good luck

3rq8 (Triarcuate)

Rita's Vintage Audio Repair is a Bob Carver Company & can repairs & updates Subs at a reasonable cost try calling them.

you must change light switch now with a new one-and grounding is very very important.