I have a circuit board I took from a broken wireless headset, and I plan of reusing it by soldering a 3.5mm plug to where the speakers was connected. So I could plugin whatever headset I want. But today I noticed that the circuit board have 4 pole/pins. L- L+ R- R+ while the plug only have R+ L+ and ground. Can I simply take R- and L- and solder them both to ground, or do I need a components to combined them first?

Normally I just trial an error, but since I only have one board I don't want to damage it by doing something dumb.

  • \$\begingroup\$ You are far better off to use separate output jacks for each channel. \$\endgroup\$ – Dwayne Reid Apr 10 '15 at 16:11
  • \$\begingroup\$ Maybe, but if I can join them to one 3.5mm I going to do it, since I want to be able to use any headset with it. \$\endgroup\$ – Yemto Apr 10 '15 at 17:04

Its difficult to say for sure without seeing the circuit, but its likely that you shouldn't do that.
My reasoning for saying that is that since the manufacturer has specifically exposed & labeled a + and - for each output, I think that each is being driven by a full-bridge/differential output amplifier.
This means that L- and R- are not simply GND/0V but are actively driven with a signal of the opposite polarity to L+ and R+.

As a simplified example, this is what I think you have for each channel:


simulate this circuit – Schematic created using CircuitLab

However, my assumption could be incorrect...
If you take a multimeter and measure the resistance between your L- and R- (with the power turned off for at least a few minutes and nothing else connected) and find that they are connected to each other internally, then you probably don't have a bridge/differential amp and it is probably safe to connect L- and R- together.


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