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19 Feb 2012 06:58:04 pm by joshie75 Merging L and R audio Quote
If I want to take the L and R from a 3.5mm audio jack, and merge the connections, I need to add in some resistors right?
19 Feb 2012 08:38:08 pm by comicIDIOT Quote
You want to go from stereo to mono audio using hardware, correct?
20 Feb 2012 12:10:01 am by christop Quote
Resistors shouldn't be necessary if you're just converting stereo to mono. All you have to do is connect the left and right wires together.

Or you could treat one of the sides as ground and leave the real ground wire disconnected so you get a mono signal that is the difference of the two channels. But that's probably not what you want to do.
20 Feb 2012 01:57:53 am by joshie75 Quote
I was talking to a friend, and he said if there are no resistors there could be a short. I don't understand how though, because if hooked together, the LR are both flowing in the same direction.

@Comic
That is exactly what I would like to do;
@Chris
Thanks Smile
20 Feb 2012 02:22:13 am by Kllrnohj Quote
joshie75 wrote:
I was talking to a friend, and he said if there are no resistors there could be a short. I don't understand how though, because if hooked together, the LR are both flowing in the same direction.


Well, technically it is a short - but that's what you want.
20 Feb 2012 02:24:02 am by ParkerR Quote
I never thought of that being a short. But yes I can confirm crossing the left and the right wires and then connecting those to a speaker + and the ground to a speaker - does work.
20 Feb 2012 03:23:41 pm by joshie75 Quote
Why is it considered a short? Thanks guys Smile
20 Feb 2012 03:25:43 pm by Aes_Sedia5 Quote
It is a short because you are crossing your hot and cold lines, which is technically, a short, although a non harmful one.

iirc
20 Feb 2012 03:28:40 pm by KermMartian Quote
joshie75 wrote:
I was talking to a friend, and he said if there are no resistors there could be a short. I don't understand how though, because if hooked together, the LR are both flowing in the same direction.
Your friend is mistaken. The resistors won't prevent the current flowing backwards, just attenuate it. Not to mention decreasing the volume on both channels.
20 Feb 2012 05:25:35 pm by joshie75 Quote
Oh I understand now.
@Kerm;
The current flowing backwards, that won't harm the input device, right?
20 Feb 2012 05:39:01 pm by benryves Quote
I'd personally connect a smallish resistor and capacitor to each side (left and right) and join those together to avoid putting undue strain on the amplifiers.

Code:
             0.1uF
L o--[100R]---||---.   
                   +---o Out
R o--[100R]---||---'
             0.1uF


I use a similar circuit (albeit with much larger resistors) to mix stereo to mono and to attenuate the signal so I can use it to connect audio output to a microphone input.
20 Feb 2012 08:04:10 pm by joshie75 Quote
Now as Kerm mentioned earlier, wouldn't those resistors lower the volume on the channels? Do the capacitors just make sure there is no backwards flow, if not, what do the caps. do?
20 Feb 2012 10:12:14 pm by Kllrnohj Quote
joshie75 wrote:
@Kerm;
The current flowing backwards, that won't harm the input device, right?


Where is this "backwards flow" stuff coming from?
20 Feb 2012 10:19:33 pm by joshie75 Quote
Well there is none, I thought Kerm was saying backwards flowing current can be prevented. I looked at my circuit and there is no backwards flowing current so I'm good there.
22 Feb 2012 06:31:31 am by benryves Quote
Adding the resistors will indeed attenuate the signal (and 100R is probably a bit high - 22R is probably more appropriate) but would protect the amplifier outputs and reduce distortion.

May I ask why you need to do this?