In the first of a few Music Technology posts, here are a few thoughts about working with levels and impedance for A Level Music Technology.
One of the most complicated topics to get your head around for A Level Music Technology is that of levels and impedance. The two things are linked, and the specification states that you need to know about microphone, instrument and line level.
When you’re working with different signals, you need to think about their difference in impedance. On equipment, it’s common to see Hi-Z and Lo-Z inputs – these are designed for different levels of input signal. Z refers to impedance. Lo-Z inputs are commonly used for microphones and Hi-Z for instruments such as electric guitar.
For your A Level Music Technology exam, you need to know about three different signal levels; microphone, instrument and line. Line level is many times louder than instrument and microphone level; these are closer together, with instrument level generally being slightly louder than instrument level. Pre-amps are used to raise or boost microphone and instrument level signals to line level, with microphone level needing more boost. Some pre-amps require you to switch between different input levels for different connectors; you should be aware of this when working.
A DI box can be used to convert from instrument level to microphone level, and thus from Hi-Z to Lo-Z. The easiest way to think about different levels (although not a hard and fast rule) is to think about the connections we tend to use when plugging equipment together; line level tends to travel through TRS jack or RCA for consumer electronics equipment, microphone level through XLR connectors and instrument level through TS jack connectors.
Some excellent further reading (that goes much beyond A Level) is here https://www.soundonsound.com/techniques/understanding-impedance.