Understanding Analog Inputs

Level: beginner

Understanding the different inputs on your audio interface is essential to avoid common problems such as clipping, noise or incorrect frequency response.


Today, most analogue interfaces have only three types of input: microphone, instrument (also known as Hi-Z) and line.

Without going into detail, there are only three parameters to worry about: impedance, input range (V or dBu) and input type (balanced or unbalanced).

  1. The input range should match the audio source and the input.
  2. Impedance should be matched using an empirical rule: the impedance of the input should be 10x higher or more than the internal impedance of the source.
  3. Use a suitable type of cable.

Microphone input

As the name suggests, it’s mainly used for microphones. Impedance is usually between 1-10kOhm, input range 1-30 mV, -58 dBu to -30 dBu. There are some common measures to consider:

  1. avoid sending line level signals, this will overload or even damage the input
  2. use balanced XLR cables to reduce noise
  3. avoid connecting an electric guitar, it may overload or damage the input, plus you will get a dull sound due to the mismatched impedance.

Instrument input aka Hi-Z

Impedance is usually 1+MOhm, input range from 0.1 to 0.775 V (-17.7 dBu to 0 dBu), somtimes higher, unbalanced cables are usually used. Some tips and tricks:

  1. use a relatively short cable (up to 5m) during recording to avoid noise
  2. if your guitar overloads the input, consider using an external DI box.
  3. do not connect instruments such as synthesizers or samplers, as you are likely to overload or even damage the input

Line input

Impedance is between 10 and 100k ohms, input range is 0.447V to 1.228V (-4.8dBu to +4dBu), and both balanced and unbalanced cables are accepted. As the input impedance is relatively low compared to the instrument input, your guitar may sound muffled when you plug it in. In this case, use the instrument input or an external DI box to match the impedance.

This technique is used:

Genres: all

Instruments: all guitar

Stages of production: recording