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Simple line mixer

This simple line mixer allows mixing of two line level audio signals together to make on audio signal. This circuit can be used to mix the audo signal from for example two soundcards, CD player, casette deck or any combination of those. This simple circuit is very easy to buils and you can even fit the components inside the RCA connectors if you are careful in construction.

To build this circuit you need three RCA connectors and two 10 kohm resistors (R1 and R2). The resistors connect the audio signals (center connector) from inputs together to from one output signal. You can see the wiring details in the figure below:

   sound card a -------\/\/\/\---+
                ---+    10K      +------------ amplifier in
                   |             |       +----
   sound card b -------\/\/\/\---+       |
                ---+    10K              |
                   |           (shields) |
                   +---------------------+

When you have connected the audio lines together using the resistors, then connect the connect the connector grounds directly together using short piece of wire.

Now you have made a nice once one channel mixer circuit. For mixing stereo signals build another identical circuit for the other audio channel.