If you would like to use your arduino or any other micrcocontroller to be able to switch your audio source, here’s a simple circuit to do the trick. This circuit uses JFET for switching audio sources. Take note that this circuit is mono, you need to build 2 for stereo.
About the Circuit
This circuit is using JFET or “junction field effect transistor” to switch between sources. R9 and R10 and C5 is used to provide half VCC voltage, if there is an existing half VCC voltage supply on your system, you can just tap it there and remove R9, R10 and C5.
You can also use this circuit for switching guitar effects circuit. You can connect input1 to the input of the guitar effects circuit and input2 to the output of the guitar effect circuit. This way you can switch the guitar effects on and off using your arduino by setting the control pin high or low.
NPN transistor can be any general purpose transistor. JFET can also be replaced by any general purpose JFET. You can also place an op-amp buffer on the input for better frequency response.
Simulation
For simulation I used simetrix as always. To simulate the audio source I used a waveform generator with different frequency to be able to distinguish the two source so you will be sure which is which is driving the output. For the switching I also a waveform generator with square wave output at low frequency. (Please take note that the numbering of components is not same with the eagle schematic)
Simulation Result
You can see that the output waveform switches because the input has different frequency. You can see which input is connected to the output.
