[yahmyxs]

If I have a set of standard headphones with mic for a PC, and I want to patch them into a 5 pin wiring plug that puts the intercom audio into them,...
Can I use a diode to keep the sound that is already going into them from the PC, from burning up the intercom, or over powering the sound and blowing up the earphones?

like>>>

earphones from PC>>>>patch into intercom>>>>diode to stop PC audio>>>>intercom on bike

I need to get my GPS in my helmet, and I want the intercom in there also.

 

[WintrSol]

So, you want to mix the intercom output with the PC output, without having one feed into the other? No, a simple diode won't do that. If the headphones are stereo, I would connect the PC audio to one speaker, the intercom to the other. The other way is to buy/build an electronic mixer.

 

[yahmyxs]

lets see, electronics class has been a while, a simple mixer is a resistor with a cap on one end and a buss on the other? maybe not a buss but a ..whats that called??!

 

[WintrSol]

The simplest mixer would be a cap to each source, connected to one end of a resistor, and the resistor grounded. From the common point, the signal would go to the load (which is also resistive); but, one source drives the output of the other in this configuration. If you want to isolate the sources from each other, with minimal cross-feed, you need, at least, two transistors, two or three capacitors, and three resistors - five resistors, if you want to control the voltage bias to the transistors. That would be for each channel, if either of your sources is stereo.

Or, you could transformer-couple the sources, with two audio transformers. There would still be some coupling between sources, though. Passive mixing loses volume from each source, though.

 

[WintrSol]

I just did a Google search for 'audio mixer', and in the images link, there were a few schematics for simple mixers.