This is going to be a tutorial on how to take a stereo audio source from a phone for example and convert it to a mono signal to use with a mono amplifier or a two channel amplifier( I'll show you how to do this), and anything that needs a mono signal. This is a cheap alternative for a stereo to mono circuit costing less than 3$, that works surprisingly well for its simplicity, even though this is not really the best way to do this. Enough of me blabbering boring stuff, onto the theory and tutorial!
You use this circuit if for example if you have a homemade boombox with a two channel amplifier that has a sub-woofer on one channel and a tweeter and a mid-range on the other. On some songs that alternate between channels, the sound will get cut off and you will not hear that part of the music, which can be frustrating. The thing to do is to make a Stereo to Mono circuit that will convert stereo to mono to play equal sound through both channels and not get any sound cut-off. This will give the boombox more range of frequencies heard through the tweeter and mid-range and not through the subwoofer which cannot be heard well. It seems confusing at first, but you will hear a difference if you are having the problem like the example above. You can also use this circuit for a mono amp like the Lm386 class ab amplifier.
The way this works is if you just join the two source stereo wires together, you will cause shortage problems as he audio sources are fighting over each other and possibly break or blow the source device, and you will have a BAD day! To counter this fighting, you put resistors on each source +, and join the two resistor ends together to have a Mono signal. This works by how the audio signals have something to pass through like a filter to prevent the audio signals from fighting like Rocky Balboa and Apollo Creed, nobody wants that.
Audio source(iPhone, MP3 player, phono plug)
2 resistors of equal value(For LINE OUPUT, use 470-1000Ω resistors.)
(For PHONE OUTPUT, use 33-100Ω resistors)
( Although anything between these values should be good)
To build this, refer to the circuit diagram that I have provided, you get a phono plug or your source and connect your resistors then connect your mono output to a mono amp or put two wires or rca from ground and two wires or rca from the output to your 2 channel amp as I explained in the example. This is an extremely easy circuit that works very well for the simplicity and the price.
So, I hope you liked this tutorial and got this circuit working, ask questions in the comments and me or anybody else will help you hopefully as soon as possible. As for the two channel example, after you hook it up, look up a left and right stereo test, if it works the sound should sound like its coming from the same speaker ans sound equal. Hope you like this tutorial and try this for your self if you need it. Thank You