Woofer is humming

Make sure that you've fully pushed in the jack to the sound card.....maybe you've not connected the jack into the correct socket on your soundcard as there are usually 3 identical sockets...but only 1 is the correct one. Sometimes colour-coded green. Try it in each one in turn. If you have headphones, try plugging them in as you will hear sound in them when you've got the correct socket!

check your audio line in connection, either L or R signal line floating may also cause humming noise. Sub woofer usually very sensitive. If your audio input not connected, do you still hear humming noise? in actual you should not hear such noise, unless volume at max then it is possible to hear little.

be more specific, what type of noise? Humming noise or cracking noise or pop noise? can you still hear noise without signal input line connected?

Very doubtful that hum issue is ground potential difference from multiple power outlets as power cord is not grounding type (it is transformer isolated). I do agree that it is good practice to connect all audio equipment to common power strip though, especially with pro sound. Check the audio cords connecting your speakers to the coumputer sound card: 1) Make sure they are connected to the correct jacks and plugged in all the way, 2) wipe the connectors off with a clean paper towel wetted with a smidge of WD-40, 3) replace cords if all else fails. I have also seen solder joints fail on the power supply capacitors (due to vibration) causing hum -- but leave this repair to an electronics technician due to dangerous voltages.

You can go buy a audioquest SUB-X subwoofer cable with a additional ground wire on it an connect the ground cable to the ground slot of the receiver an the other end to a screw on the sub or into one of the high output terminals on the woofer if it has them an this will take that humming sound right away but the cable is around $90

Select Start > (right click) My Computer > Manage
In the Management window select > Device Manager
Next to Sound, Video and Game Controllers click the + sign
A yellow triangle will signify a problem so if one is present, right-click that device and select Properties
You can then choose to update the driver
For more details check Dell Xps 420 Manual.
Dell Xps 420 Manual

the conections some where are dirty you need to unplug everything clean all connections and the hum will go away

check the NPN and PNP transistor output maybe shorted.....

Hi There, Please advise us what happens when you turn off the sub woofer is the hum still there....??

From YUBEUT.

Check capacitors in power supply......also check for over-heated
resistors..all 1 ohm.....replace if cooked...................T.