The two key parts of the box are:

1. A 5 or 6 volt regulator (Figure 16).

Figure 16: Voltage regulator

2. A Ground Loop Isolator (GLI) (Figure 17).

Figure 17: Ground loop isolator

The ground loop isolator serves two purposes. First, you don't want the 5-6V DC going back into your audio source (your soundcard), so the ground loop isolator acts as a DC filter to protect your sound card or audio source from being fried by the voltage from the regulator. Second, you need the isolator to break any ground loops and filter ignition noise so that your audio is clean. The schematic for the entire Monsoon audio adapter is shown in Figure 18.

Figure 18: Monsoon input box schematic

So now that the 5V DC injector is built, you need to connect it to the Monsoon amplifier. But, of course, the Monsoon does not use RCA connectors like most amplifiers do. In our case, VW uses its own special connector. After a good amount of digging, it turns out that it is the same connector that is used for the VW's ECU (Engine Control Unit). Once we had the part numbers, we went to the local VW dealer and had them order the parts for us:

1 of 1J0-962-624-A. This is the grey connector itself, with no wiring. 6 of 000-979-131. This is wire with female pins that lock into the connector. We only needed 4

To power the unit, we tapped power from one of the 12V four-pin Molex connectors. One thing to note is that the ground must always be connected, or the amplifier will not turn off, and it will drain your battery in a matter of hours.