Audio Mixer Upgrade

Introduction

It seems the audio industry has a hard time adjusting their product lines to meet the needs of computerized homes. For a long time I have been searching for a simple 3 input stereo audio mixer, to hook up two computers and a mp3 player to the same speaker system without having to switch between the sources as you would have to on an old fashioned amplifier.

Recently I came across a small audio mixer that was close enough to what I wanted to make me buy it:

profitec TC 23 Stereo Camcorder Audio Mixer

This device provides 2 stereo inputs and 1 mono microphone input, but - as I found out - can easily be upgraded to 3 stereo inputs.

Upgrade Instructions

Little is needed for the procedure:

• 3.5mm stereo headphone jack (a short one, like in the pictures on the side)
• some wire

This is what the circuit board should look like:

1. here the amplified mono microphone signal is fed into the third stereo slider, with left and right channel short circuited
2. microphone mono pre-amplifier
3. left channel output amplifier
4. right channel output amplifier

The first step is to cut the connection between the microphone pre-amplifier output and the third slider (1) and remove the short circuit between left and right channel (2):

Next the old mono microphone jack ist removed from the case and the new stereo one is being mounted. See the picture below for information on how to wire it to the board, which is the final step:

Yellow is being used for Ground (the contact closest to the outside of the case in the jack), green is being used for the right channel (in the middle of the jack) and blue for the left channel.

That's it. A portable mp3, cd or whatever player can now be hooked up to the front jack.