8. The Audio

In most cars, to get an audio system befitting use with a CarPC, we would have needed to put in an aftermarket two or four channel amplifier, which would be installed using regular car audio techniques. Alternatively, your radio may have auxiliary inputs to which you can connect the CarPC, or your factory audio system may have an input device that takes the place of a CD changer. In our case, our VW had a Monsoon audio system, which we were able to tap into.

Note: the following will only apply to cars that have the Monsoon audio system.

To turn on the amplifier, you need to inject 5-6V DC into the negative line of your audio signal. Since the 1/8" headphone plug that goes into soundcards has a common negative conductor anyway, I tied all the negative input lines on my Monsoon amp together. To enable the use of the factory amplifier in the vehicle, we also had to create a custom input box (Figure 14).

Figure 14: Monsoon input box all assembled

Figure 15: Monsoon input open