I need a little help with a circuit I'd like to design.
Here's a little background:
At work, I spend a good portion of my time on the phone. I use a headset that has one earpiece and a mic boom. The connection from this headset is a TRS 3.5mm minijack (aka a stereo minijack), and this connects to a special phone amplifier/adapter.
What I'd like to do is be able to:
1. Use a normal, stereo headset with boom mic, and
2. Listen to music in stereo while taking phone calls.
The headset that I want to use has separate connectors for the mic and headphones, so I built a small adapter box. The telephone amp connection is like this:
...so I tied tip and sleeve to a jack to plug the mic connector into, and I tied ring and sleeve to the headphone jack. I then tied another jack into the headphone jack so I could connect another audio source (but not have it feed into the phone amp).
The problem I ran across is this: When I plugged the headset into the phone amp, it worked great. But as soon as I plugged in the 2nd audio source (in this case an iMac), it killed not only the phone amp but the iMac's sound controller.
I'm positive that the polarity is correct and that all the solder joints are good. I think the problem is that I need to isolate the phone audio from the computer audio when they reach the headphones.
So this is where I need some help. Anyone know of a simple circuit that I can build that will effectively mix two audio (headphone-level) signals? Source one would be mono audio (tied to go to both headphone drivers) and source two would be stereo (which I would want to keep stereo).
If this description causes confusion, I can draw up a schematic of what I made to clarify.