New user - basic stereo/mono audio mixer question

[RadioChris]

Hi, I have several audio sources (radios) and one stereo source (computer). I could not find a basic stereo mixer so bought parts to build one including a small "headphone amplifier" to boost the signal back up since each source will pass through resistors to prevent them from interfering each other (this is from a passive mixer design found all over the net). http://www.instructables.com/id/Altoids ... reo-Mixer/

I plan to have a toggle switch for each left and right channel even though most sources are mono. That way I can feed one radio to my left ear and another to the right to compare signals.

The issue I need answered is that I need to keep the stereo source isolated, so it stays stereo even if both channels of a mono source are fed to both headphone sides. It seems to me that when a mono source is switched to feed both sides, then my headphones will become mono through that source and the stereo will mix to mono.

Is there a way, such as with diodes or some method to allow mono source to push to both headphone sides while the stereo source does the same only doesnt tie together back before the l/r switches for that mono source.

This is only an issue when a mono source has both l/r switches closed typing both headphone sides back together.

Hopefully I've made the problem clear enough!

[pebe]

I plan to have a toggle switch for each left and right channel even though most sources are mono. That way I can feed one radio to my left ear and another to the right to compare signals.

You don't need a toggle switch. Use the mixer as-is. Feed one radio to the tip of one plug and the other radio to the ring of another plug. That will give the two radios separately on left or right channels.

Is there a way, such as with diodes or some method to allow mono source to push to both headphone sides while the stereo source does the same only doesnt tie together back before the l/r switches for that mono source.

If you want a single mono source to go to both channels, connect its output to both tip and ring of one plug so that the output goes to both channels.

[RadioChris]

Thanks for the reply, but you may have not read my description. This is a unit to mix approx FIVE radios, and ONE is stereo, the rest are mono.


I would like the ability to hear the stereo source in stereo, and select in one or more of the other four sources to one ear or the other.

Think of it this way, the stereo will be playing classical music while one mono radio is on both ears. How can I prevent the left/right stereo channels from being combined by the mono channel (which ties l/r together). Thats why I emntioned a "diode" or some other way to isolate the stereo from the mono. Is that making any sense?

[pebe]

I read your question carefully. It seemed that your requirements in paras 2 and 4 were different, so I gave you two solutions.

Look at my reply again and if it still doesn't make sense let me know and I will draw it out for you.

Incidentally, you will not get perfect separation of channels using a simple resistive mixer.