The Aerpro AP3042A is a super compact 2-channel line output converter. Ideal for adding aftermarket amplifiers to factory headunits in most 12V vehicles. Many aftermarket amplifiers only have a low voltage audio input, this can be problematic when the factory headunit can not be changed or is preffered over aftermarket headunits. The AP3042A converts a high voltage signal from a factory headunit to a low voltage signal suitable for most aftermarket amplifiers. The built-in signal noise filter helps to reduce unwanted noise commonly picked up from factory headunits. The Step Down adjustable channel gain makes the AP3042A compatible with most aftermarket amplifiers and can also help adjust the signal voltage for individual channels.