Simple Audio Mux

[LMC13]

I need to make a basic audio mux, which will drive an 8-ohm .1 or .25W speaker from two different sources. Both sources will not drive at the same time. This is for a novelty device, so it has to be cheap. Sources might be either differential or single ended. Anyone know a simple circuit to do this?

I appreciate any help!

 

[Tim__x]

Are you looking for a mixer or a multiplexer (Mux).
A multiplexer turns one source off and another on. A mixer outputs the sum of all inputs. If none of your inputs need to be muted then a multiple input inverting amplifier will do.

 

[pinkmouse]

Exactly. Do a search on virtual earth inputs/mixers.

 

[LMC13]

Only 1 source will drive the speaker at a time, so it would be a multiplexer rather than a mixer. I'd rather use discrete transistors than monolithic dual input amp for the sake of cost. I do have a digital control signal, which I can use to select which source would drive the speaker.

I'm not sure what searching on virtual earth means. www.virtualearth.com is a link to some sort of microsoft website. A search on yahoo for virtual earth doesn't yield any technology web sites (at least not in the first couple pages). I search for it here on diyAudio.com and came up blank too.

Thanks for the replies and help!

 

[Tim__x]

You probably don't need a multiplexer. Like I said before, you only need a multiplexer if one source must be muted while the other plays. If one source is quiet while the other one is playing then you don't need muting and a mixer will work.

http://en.wikipedia.org/wiki/Virtual_ground

http://en.wikipedia.org/wiki/Operational_amplifier_applications