i have a pioneer premier DEH-P770MP headunit and it says it has 4 volt preouts does that mean that i should set my amps input sensetivity to 4 volts? input sensetivity is also know as gain correct?
Input SENSITIVITY (note spelling), is different from gain. Most people use the two interchangeably.
When you adjust how sensitive something else, you're not affecting maximum output capability of the device. The max output power before clipping is fixed. You adjust sensitivity so you don't over drive the amp.
Gain on the other hand is an amplification factor.
Both will increase the power of the output, but where the adjustment is made I believe determines what it's called.
If you're matching two signal levels, I call it sensitivity. If you're trying to adjust the output level of something then it's gain.