Stereo to Mono Adapter

As most of you know I have a auxiliary amp that is also used as a second sub woofer. I have found lately that I don’t always want to plug my laptop into the 5.1 surround sound and blast the bass and every thing else through the house. So I have made an adapter for anything with a stereo controlled out put to be converter to Mono. (one channel)

Now here are the specs on the amp.

  • 1/4 inch input
  • 100 watts (single Channel)

This is what you going to need.

  • Stereo head phone cable (Left, Right and Ground)
  • 1/4 inch mono plug male
  • 1/4 inch stereo plug female (can be 3.5mm if you want to plug in a CD player or something
  • two 10k resistors
  • solder iron

Okay now I’ll lay out the rest of the process into steps.

Step 1

Cut a length of the head phone cable about 1 foot long. (or how ever long you need to go). Then strip the first jacket of insulation off then you should see one with no insulation, one with red insulation then another with white insulation. You will want to twist the ground (no insulation) together so there tight. Next strip the insulation off the red one then twist it together. Do the same for the white. Then do the other end.

Step 2

We are going to do the easy part first. Take the female stereo end and solder it to one end of the cable. Make sure the ground (no insulation) goes to the ground of the plug. Some are tabs right off the metal case.

Step 3

Next will be the complicating part. Take one of the 10k resistors and solder it to the red lead at the other end of the cable. Next take the second 10k resistor and solder it to the white lead. Then twist the ends of the resistors together. Make sure that before the resistors aren’t touching. I taped myna very well so they wouldn’t touch.

Step 4

Next solder you ground to the out side shield of the 1/4 inch male end of the plug. Then solder your twisted 10k resistors to the tip tab on the plug. Slip the covers over top of them. (or tape them 😛 )

Step 5 (only if you have the equipment)

Get out a voltmeter and set it to Ohms. Next you will want to check the grounds to make sure there not shorting out the audio.


Now if every thing checks out and you are confident, plug the adapter into your amps Line level input. Next tern the volume down on you devise. (CD player, Laptop, Tape deck, etc.) Remember to use the headphones output so you can control the volume. Then plug the other end into you devise. Now tern on the devise then the amp. Now run away just encase it ignites. 😛 Now insert a CD or whatever your using that as a part where it uses only the left or the right. In this case I used Queens – Fat Bottom Girlss .

That should be it. If you have any problems, feel free to post them on the forum. Here are a few pictures of the final product in use.