[b3lha]

Originally Posted by Trevor

Or is your input impedance/loading too low i.e. too sensitive. A higher relative loading would pull down the output/input signal voltage. This could be where the Subaru OEM monitor differs. The fact that you indicate that a zero voltage is not being recorded, points in this direction.

The lower the monitor input impedance/resistance; the greater the signal current; lower the voltage (Dependent on output capacity) and greater the immunity to noise. In all respects the transmitted signal is more robust, a worthwhile feature.

In other words, the existing signal could be overloading your gear. Think of the affect of overloading the input of an audio amp.

I think I understand what you are saying Trevor. How would you go about modifying the circuit to improve matters?