Charlie, the lead guitar player in my band, Box of Birds, does live sound. He asked me a question the other day that unleashed my brain into a black hole of information that I wanted to try to share with you today. The question he asked was, “What is the difference between mic level and line level?”
Mic and line level are really just descriptions of voltage. Of course, voltages, just like any form of energy, audio, motion, etc, fluctuates. The way levels are described has to do with an overall average of the voltage generated--in the case of microphones, voltage generated by the change in air pressure on the diaphragm of the mic when we make noise in front of it.
Microphones are transducers, which basically means that microphones convert energy from one form into another. Let’s imagine for a second you’re talking into a microphone. When you speak, the air molecules start bumping into each other creating a change in air pressure (when the molecules get really close to each other, there’s a compression and when they are far away from each other there is a rarefaction. When those molecules run into the diaphragm on our mic, the diaphragm gets bumped as well and moves. Electronics inside the mic convert that movement into electricity, creating a voltage. Let me be totally clear. It is a super super tiny amount of voltage, much too small to ever be able to hear without amplification. That’s why we use a pre-amp in order to boost the signal to line level.
That brings us up to line level. Line level is basically an audio signal’s standard created by the powers that be. The goal of anything that we want to hear out of speakers is to first get it to line level because line level is much more easily manipulated than such a small signal like mic level and has a low-impedance (low resistance), so voltage can travel easier, unlike something like speaker level--I’ll talk more about that in a second.
The thing to remember is that the output of mic-pres are line level, and all the other audio equipment in consoles and outboard gear take and send line level (unless it is otherwise specified).
Once you’re ready to hear the stuff out of the speakers, the power amp for the speakers will amplify the line level into speaker level. Just like microphones, speakers are transducers as well. They work in the opposite way that mics work in the sense that they will convert the voltage into movement of the diaphragm of the speakers in order to create air pressure changes that our ears then hear as sound.
That’s all for today. This is a dense topic but hopefully this made sense. Thanks for reading, and if you have any questions, feel free to reach out!