Let me preface by saying I am a total noob at this stuff. I work at RadioShack and goof off with it when I am bored at work.
Anyway, I have a problem with my home computer. I have a soundcard that has 1 input and 1 output. However, going into that 1 input I constantly swap between my XBox360 and my microphone. And the 1 output is witness to a constant battle between my headphones and my speaker.
So, one day at work I decided to make a selector switch that I could just plug all of my stuff into and flip a couple switches to choose, instead of all the fuss and muss of pulling my computer out every time I needed to make the switch.
So, what I have is a black box with 2 1/8" TRS jacks on the back. They go to the microphone and headphone jack on my soundcard. On the front of the box is 4 1/8" TRS jacks. All the jacks are the standard open circuit style (when there is nothing plugged in the circuit is open, it is closed by the tip when a device is plugged in). Then I have 2 DPDT switches on the top (one for mic/xbox the other for headphone/speakers obviously).
It works perfectly, except for one minor annoyance. When using my headphones there is very faint noise on the line. The level of the noise doesn't change if I turn the volume up or down on my computer. The noise stops completely if I unplug the speakers from the box though. I have checked and found no shorts. I suspect that it is caused by the way I wired the circuit.
The TRS jack has 3 connections, left channel, right channel, ground. Now, on my switch it is DPDT so there are 2 connections per side of the switch. Thinking it wouldn't be a problem I soldered the ground wire from both of the front audio jacks to the ground wire of the rear output audio jack. I suspect this is the cause of the interference.
Any ideas on the cause of the interference or a way of solving the problem?