In the audio world there are actually four different signal levels that are relevant. The two most discussed in regards to input are line level input and microphone input. First, lets take a look at all four:
- microphone level - weaker audio level than line, such as that from a microphone
- instrument level - weaker audio level than line, such as that from instrument pickups
- line level - used to interconnect audio components
- speaker level - an amplified audio signal for headphones and speakers
Microphone and instrument level audio is weaker than line level. The signal strength can refer to voltage and impedance to produce output power.