I have a project for you all: Humming Noise when Connecting Speakers to Subwoofer

[Kestrel-7]

Here's the background:
I received the GoGroove basspulse more than a year ago for Christmas. It comes with both a subwoofer and speakers. This was a pretty cool setup because the speakers just plugged directly into the subwoofer and then the subwoofer plugged into the wall. There was also a button on the subwoofer which could be pressed to turn on LEDs on the speakers. But recently, one of the speakers died. So then I got new USB powered dell speakers, thinking I would be able to just plug the USB into a wall adapter and then the audio jack into the subwoofer.
This actually worked really well, but the downside is that now there is a persistent humming sound. This wasn't there with the speakers that came with the basspulse.

Here's the complicated set-up:

(Mirror if the image isn't working)

I've already done quite a bit of experimenting so I'll just lay out everything I know so far:
I've plugged both my speakers and subwoofer into the same outlet (A) and the Hum persisted. I've plugged my speakers, subwoofer, and monitor into the same outlet and the Hum persisted. I also tried adjusting the volume on each component and the only thing that silences the Hum is the volume wheel directly on the speakers. The Hum is also present when I plugged headphones into my subwoofer. So I really don't think that there's a ground loop. The problem is with that 3.5mm audio port on the back of my subwoofer where the speakers and headphones were being plugged into. I also noticed that on my old speakers that came with the basspulse, there are three rings on the jack head whereas my new speakers only have two rings. Usually, three rings means there's a microphone connected. But there was certainly no microphone connected those old speakers. My guess is that that third ring had something to do with the speaker LEDs that turned on when the button on the subwoofer was pressed. One more thing, there's no hum when new speakers are plugged in directly to my computer or monitor.

So what are you guys' thoughts?
Is there a relatively cheap solution for getting rid of this hum? Or will I just have to live with it?

Any questions for clarification are welcome and I can also post pictures if you think you'll need those.
Thanks in advance!

 

[soccerkingpilot]

Are any of your power lines crossing over signal lines to the sub or speakers?

 

[ricdiculus]

I suspect your right about the third ring being used for the LEDs. So when you plug-in a 2 ring plug, the LED and ground are probably getting shorted out to each other, inducing the hum. Not really a ground loop, but you are adding some type of signal to the ground of the sattelite speakers, and since those speakers are powered, they are amplifying the hum as well. This is why they sound clean when you connect them to something else. The only thing I can think of to fix this, would be to replace the 2 ring plug with a three ring plug, just dont connect the third ring to anything. This should isolate the LED signal from the audio signals ground. In theory...

 

[americanaudiophile]

The USB speakers are self powered. The original speakers don't seem to be self powered. The amp for them is probably in the subwoofer.
If you want to get rid of the hum a speaker to line level converter in between the sub and speakers should work. Or get passive speakers,

 

[ricdiculus]

didnt think about your original speakers being passive. If thats the case, americanaudiophile has got the solution.

 

[Kestrel-7]

The USB speakers are self-powered. The original speakers don't seem to be self-powered. The amp for them is probably in the subwoofer.
If you want to get rid of the hum a speaker to line level converter in between the sub and speakers should work. Or get passive speakers,

I'll probably try to avoid getting new, passive speakers. That's probably why the old ones eventually died down and got pretty weak.
But could you expand on what exactly a line level converter is and how it would help? And could you suggest where I could find a fairly cost efficient one?
Also, do you think I could just open up the subwoofer and cut the amp off? Would that be possible?
Thank you, again.

 

[americanaudiophile]

This is an example of a speaker to line level converter
https/www.crutchfield.com/p_142LOC80/Scosche-LOC80.html
They are very common in car stereo.
You could bypass the amp in the subwoofer but it might not be obvious where to do that.
A schematic might be needed.

 

[Kestrel-7]

This is an example of a speaker to line level converter
https/www.crutchfield.com/p_142LOC80/Scosche-LOC80.html
They are very common in car stereo.
You could bypass the amp in the subwoofer but it might not be obvious where to do that.
A schematic might be needed.

There's no schematic but I can give you a few pictures of the inside: http/imgur.com/a/RSHGN

 

[Kestrel-7]

Alright, so what I did was just get an audio jack splitter in order to plug the speakers and subwoofer into the same input.