Cannot eliminate hum from audio mixer.

[Raziaar]

Okay, so I have bought this stereo mixer, along with the following cables to go with it

http/www.amazon.com/gp/product/B0002CZQJ6/ref=oh_details_o08_s01_i01?ie=UTF8&psc=1

http/www.amazon.com/gp/product/B005HGM1D6/ref=oh_details_o08_s01_i03?ie=UTF8&psc=1

I have three things being plugged through this mixer. One into my computer, one into my Lenovo laptop, and one that I'm trying to plug into my xbox 360.

I had to fiddle a great deal with it with my computer and laptop, but I did manage to eliminate the humming i would experience listening through my Sennheiser HD280 Pro headphones. I'm experiencing the same problem now when trying to add the Xbox 360 into the mix.

If I unplug the xbox 360 audio cable(which isn't even plugged into the machine yet), there is no hum, and if it's plugged in and I unplug in the audio cable going into my computer, there is no hum. It seems to be when both are plugged in, that there is a noticeable hum.

I thought maybe it was poor quality cables, but everyone seems to experience great results with these cables on Amazon. I have avoided as much as possible any cable crossover with power cables, and yet I still hear the hum.

One thing that troubles me, is that if I rotate the 3.5mm jack that is plugged into my computer, on some spots of rotation the hum will come in.

How do I isolate and eliminate this humming? It's driving me insane!

 

[risaccess1]

This sounds like the hum is probably being caused by a ground loop. I have had plenty of experience with this and I can usually solve the humming problem with a line transformer. However, I see no practical way of adding a transformer to this scenario. Check the grounding pin on everything you have plugged in (the third prong) and make sure you are not doing anything weird with 3 prong to 2 prong adapters. Also, dust off all the connections and blow anything out of the jacks. If all else fails, you could try getting a 3.5mm transformer from a company like Hosa.

 

[Raziaar]

This sounds like the hum is probably being caused by a ground loop. I have had plenty of experience with this and I can usually solve the humming problem with a line transformer. However, I see no practical way of adding a transformer to this scenario. Check the grounding pin on everything you have plugged in (the third prong) and make sure you are not doing anything weird with 3 prong to 2 prong adapters. Also, dust off all the connections and blow anything out of the jacks. If all else fails, you could try getting a 3.5mm transformer from a company like Hosa.

A funny thing I noticed as well recently, with my setup, is that when my PC shuts down, I get these almost electrical sounding popping sounds in my headphones, like a taser.

I also notice that I experience sound from doing things, for example, like changing the speed on my ceiling fan. I never noticed these things before when I was simply plugging my headphones into my PC.

 

[risaccess1]

Yes. The popping is normal, its just a minor surge in the signal because the PC is turning off. If it bugs you, just unplug headphones before shutting down.
What you described with the ceiling fan indicates electrical interference on the power lines in your home. Electricity travels in a 3 phase sine wave, but appliances such as electric motors( ceiling fan) will create these "ripples" in the current which is what you hear in the headphones. (like a buzzing)

 

[Raziaar]

Yes. The popping is normal, its just a minor surge in the signal because the PC is turning off. If it bugs you, just unplug headphones before shutting down.
What you described with the ceiling fan indicates electrical interference on the power lines in your home. Electricity travels in a 3 phase sine wave, but appliances such as electric motors( ceiling fan) will create these "ripples" in the current which is what you hear in the headphones. (like a buzzing)

I seem to have isolated the audio noise source to the VGA cable of the xbox 360 cable, when I connect it into one of my monitors.