This applies to All interfaces

Focusrite interfaces have different types of inputs that allow you to plug in a variety of audio sources. The types of input include:

• Mic (microphone)
• Line (line level)
• Inst (instrument). 

Our “combo inputs”, with an XLR and 1/4” jack inputs, will have a hardware or software button to change between input types. You need to change the input type when you connect a different source to that input. For example, if you disconnect a synthesiser and connect your guitar to a 1/4” jack input. 

Input Type Descriptions 

Mic Level is the lowest signal level. This travels through an XLR connection and requires a preamp to boost the signal to 'Line Level'. This input is used to connect microphones to your interface. Many of our interfaces will not have a “Mic” setting, as the XLR input will always be set to mic level and impedance by default.

Line Level is the highest signal level that travels through a TRS (Tip, Ring, Sleeve) jack connection. This should be used when connecting any non-instrument devices to your interface (i.e., an outboard preamp or processor) or instruments that output line level (synths, keyboards, drum machines etc).

Instrument Level is the most variable level signal which will travel through a TS (Tip, sleeve) jack connection and will also require a preamp to be raised to Line Level. “Inst” should be selected whenever you connect an instrument, such as a guitar or bass guitar, directly to your interface.

Input Type Differences 

The input type choice changes the characteristics of the input to accommodate the source you connect. The characteristics that change will affect the signal in 2 main ways: 

• Impedance - The impedance needs to change compared to the input, so it sounds correct. For example, an input set to 'Inst' will change its impedance to match a guitar amp, so your guitar sounds natural.  
• Maximum input level - various sources will output at different electrical levels. A synthesiser will output more level than a guitar, so to ensure the best quality signal, we can adjust the maximum level the input accepts to make the most of the input gain. 

The following table details typical values for impedance and the maximum input level on Focusrite Audio Interfaces. The exact measurements will depend on your interface or input and will be listed on your product's website or user guide. 

Further Reading

Sound on Sound magazine has a more in-depth article on this topic here:

Q. Do I need to think about matching mic and preamp impedances? (soundonsound.com)