Excellent signal to noise ratios
High level/low level input
Aux input
Adjustable gain output

This is a Line Output Converter with an adjustable Line Driver built in. You can hook this up to your factory stereo to get signal to convert into your aftermarket amplifier. 
Or you can also plug your phone into this device with me 3.5mm to RCA cables, or a Bluetooth receiver, and then use this to adjust the signal level to match what your amp needs. These work great!