Mic, Line, or Instrument? Making the Most of Your Audio Interface Inputs

In the world of music production and recording, the audio interface serves as the bridge between the physical world of sound and the digital realm of music production software. 

As the main hub where microphones, instruments, and other audio devices connect, understanding the different types of inputs on an audio interface is key to achieving the best possible sound quality. 

How many inputs do I need on my audio interface?

The number of inputs you need on your audio interface depends on the number of instruments or voices you plan to record simultaneously. For solo performers, one to two inputs may be sufficient, while recording a full band live may require eight or more.

In this article, we’ll explore the various types of inputs—mic, line, and instrument—and discuss the different scenarios where you might use each one. It will help you understand how to effectively connect and record your audio sources for optimal results.

focusrite audio interfaces

How Many Inputs Do I Need On My Audio Interface?

The number of inputs you need on your audio interface depends on what you plan to do with it. 

Here are some things to consider when determining how many inputs you need on your audio interface:

  • The number of instruments you will be recording: If you are recording a full band, then you will need at least 8 inputs. However, if you are only recording one or two instruments, then you can get away with a smaller number of inputs.
  • The type of instruments you will be recording: Some instruments, such as drums, require more inputs than others. For example, a drum kit with 5 toms and 2 kicks will require at least 7 inputs.
  • Your budget: Audio interfaces with more inputs tend to be more expensive. If you are on a budget, then you may want to consider an audio interface with fewer inputs.

Here are some common scenarios:

  1. Solo Musician/Singer-Songwriter: If you are a solo musician or a singer-songwriter who records one instrument at a time, a 2-input interface should be sufficient. This would allow you to record, for example, a vocal and a guitar at the same time.
  2. Podcaster: If you’re a podcaster who only records your own voice, you might only need one input. However, if you often have guests, you might want a 2-input or even a 4-input interface to allow for multiple microphones.
  3. Band Recording: If you’re recording a full band live, you’ll need an interface with enough inputs to handle each microphone and instrument. This might mean needing 8, 16, or even more inputs.
  4. Electronic Music Production: If you’re producing electronic music and mostly use software instruments (VSTs), you might only need 2 inputs for the occasional live instrument or vocal.
  5. DJ: If you’re a DJ using a digital setup, you may only need 2 inputs for your decks. However, if you plan on adding more decks or additional instruments, you may need more.
  6. Sound Design/Foley: If you’re doing sound design or foley work for film or games, you might need multiple inputs for different mics to capture a wide range of sounds.

Your specific needs will vary depending on your setup and workflow. Keep in mind that it’s often a good idea to have a couple of extra inputs available for flexibility in the future.

If you are not sure how many inputs you need, it is always best to err on the side of caution and get an audio interface with more inputs than you think you will need. This will give you more flexibility in the future if you decide to record more instruments.

What Is The Benefit Of Multiple Audio Inputs On An Audio Interface?

Multiple inputs on an audio interface can provide several benefits, especially for recording multiple instruments or voices at once. Here are a few of the main advantages:

  1. Simultaneous Multi-track Recording: With multiple inputs, you can record multiple tracks at the same time. This is essential for recording a band live, for example, where you might need to capture vocals, guitar, bass, and drums all at once. Each instrument or microphone can have its own dedicated input, allowing you to mix and edit each one individually later.
  2. Flexibility: Having multiple inputs provides flexibility. You might only need one or two inputs for a basic recording, but having more allows you to expand your setup if necessary. This can be useful if you decide to add more instruments or if you have guests and need to record more voices.
  3. Different Types of Inputs: Different inputs can accept different types of audio signals. For example, some inputs are designed for microphones, while others are designed for line-level signals from instruments or other audio devices. Having a variety of inputs can give you more options for connecting different audio sources.
  4. Stereo Recording: If you’re recording a stereo source, like a piano or a drum kit, you’ll need at least two inputs. This allows you to capture a more realistic and immersive sound.
  5. Backup: If one of your inputs fails for some reason, having multiple inputs means you can switch to a different one and continue recording.

If you are looking for an audio interface with multiple inputs, there are many great options available. Some popular models include the Focusrite Scarlett 18i20, the PreSonus Studio 1620, and the Universal Audio Apollo Twin X.

When choosing an audio interface, consider the number of inputs you need, the type of connectors you need, and your budget. It is also a good idea to read reviews of different audio interfaces to get an idea of how well they perform.

While more inputs can provide more flexibility, they also make the interface more expensive and potentially more complex to use. You’ll need to balance your actual needs with your budget and comfort level.

What Can You Connect To An Audio Interface?

An audio interface serves as the hub for your recording setup, and you can connect a variety of devices to it, depending on the interface’s input and output options. Here are some common devices that you might connect:

  1. Microphones: This is probably the most common device to connect to an audio interface. Microphones capture vocal performances, acoustic instruments, or any other type of sound source you want to record.
  2. Electric Instruments: Electric guitars, bass guitars, and certain types of keyboards can be connected directly to an audio interface.
  3. Line-level devices: Audio interfaces also typically have one or more line-level inputs, which can be used to connect line-level devices such as mixers, synthesizers, and other audio equipment to your computer. This is a great way to add external effects to your recordings or live streams.
  4. MIDI Devices: Some audio interfaces have MIDI (Musical Instrument Digital Interface) inputs and outputs, which allow you to connect devices like MIDI keyboards, drum machines, and other controllers.
  5. External Hardware: This could include outboard preamps, compressors, EQs, and other effects units. These devices can be connected to the line inputs/outputs of your interface.
  6. Monitors (Speakers): Studio monitors are connected to the outputs of your audio interface. This allows you to listen back to your mixes in a controlled environment.
  7. Headphones: Most audio interfaces have at least one headphone output for monitoring your recording and playback.
  8. Computer: The audio interface connects to your computer, typically via USB, Thunderbolt, or Firewire. This allows you to send audio back and forth between your computer and the interface for recording and playback.
  9. Synthesizers/Drum Machines: These can be connected to the audio inputs of your interface, allowing you to record their output. Some of these devices may also be connected via MIDI.

The specific devices that you can connect to an audio interface will depend on the audio interface itself. However, most audio interfaces will allow you to connect a variety of different devices, giving you the flexibility to connect the audio equipment you need to create your music.

What Are Line Inputs On An Audio Interface?

“Line inputs” on an audio interface refer to a type of connection that is designed to receive a specific level of audio signal, known as line level. Line level is the specified strength of an audio signal used to transmit analog sound between audio components such as CD and DVD players, television sets, audio amplifiers, and mixing consoles.

Line-level signals are typically much higher in amplitude than microphone-level signals, and they do not require as much amplification to be dealt with by the rest of the audio interface. As such, on some audio interfaces, the line inputs actually bypass the microphone preamp stage providing a pure signal path into the board.

There are two types of line level signals:

  1. Consumer Line Level (-10dBV): This is typically found on consumer-grade equipment like home stereo systems.
  2. Professional Line Level (+4 dBu): This is used in professional environments like recording studios and broadcast stations. It’s a stronger signal than the consumer line level.

Audio interfaces often include line inputs because they allow you to connect a variety of devices that output a line-level signal, such as synthesizers, drum machines, and effects processors. 

These inputs can also be used with external microphone preamps, where the preamp boosts the microphone-level signal up to line level before it reaches the interface.

Line inputs are typically used for two purposes:

  1. To record audio from line-level sources: This is the most common use for line inputs. By connecting a line-level source to an audio interface, you can record the audio from that source to your computer.
  2. To send audio to external effects: You can also use line inputs to send audio to external effects. This is a great way to add effects to your recordings or live streams.

Line inputs are different from microphone inputs (which are designed for the much lower-level signals that microphones produce) and instrument inputs (which are designed for the higher impedance signals from electric guitars and basses).

Line inputs are usually balanced, meaning they are less susceptible to noise and interference. This is particularly important in professional and studio environments where cable runs can be quite long.

If you are looking to connect line-level sources to your audio interface, then you will need to use line inputs. Line inputs are usually labeled as “Line In” or “Line Input.”

Here are some of the benefits of using line inputs on an audio interface:

  • Higher signal level: Line-level signals are typically much higher in amplitude than microphone-level signals. This means that they can be recorded with less noise and distortion.
  • Less preamp gain required: Because line-level signals are already at a higher amplitude, they do not require as much preamp gain to be recorded. This can help to prevent distortion and noise.
  • More flexibility: Line inputs can be used to connect a variety of different sources, including synthesizers, mixers, and external effects. This gives you more flexibility in your recording and mixing process.
Focusrite Scarlett Gen2 2i4 and Gen3 4i4

What Are Instrument (Inst) Inputs On an Audio Interface?

“Instrument” inputs, often labeled as “Inst” on an audio interface, are specifically designed to handle the signals coming directly from electric guitars or basses. These inputs have a high impedance (also called “Hi-Z”) to accommodate the pickups in these instruments.

Instrument-level signals are typically much lower in amplitude than line-level signals, and they require a preamp to be boosted to line level before they can be recorded or processed.

Electric guitars and basses have a unique signal level and impedance that’s different from microphones and line-level devices. The signal is much lower than line level but higher than a microphone signal. Additionally, the impedance of guitar and bass pickups is much higher than other audio sources.

When you plug an electric guitar or bass directly into a line-level or microphone input, it can result in a weak and thin sound because the mismatched impedance loads the pickups and alters their frequency response. 

Instrument inputs solve this problem by matching the impedance of the guitar or bass pickups, ensuring that the signal is accurately captured.

If you’re using a guitar or bass amplifier or an external DI (Direct Injection) box, you might not need to use the instrument input on your audio interface. An amplifier typically outputs a line-level signal, which you would connect to a line input on your interface instead.

DI-boxes output a lower impedance signal. Your interface has an Instrument level input already. DI boxes are for impedance matching, and you already have an instrument-level input designed for high impedance.

A DI-box is a redundant piece of gear that isn’t going to change your sound.

Should I use line or Inst for vocals?

For vocals, you would typically use neither a line input nor an instrument (Inst) input. Instead, you would use a microphone input.

Vocals are usually recorded using a microphone, which produces a mic-level signal. This signal is much weaker than a line-level or instrument-level signal, so it needs to be amplified before it can be recorded. 

A microphone input on an audio interface is designed to accept this weak signal and amplify it to a usable level. This process is known as preamplification or “preamp.”

When you plug your microphone into the microphone input on your audio interface, the interface’s built-in preamp boosts the mic-level signal to line level, which can then be properly processed and recorded.

So, for vocals, you would generally use a microphone connected to a microphone input on your audio interface. You would not typically use a line input or an instrument input for this purpose.

In the case of some audio interfaces, such as the Focusrite Scarlett series, the interface automatically switches to a mic preamp whenever you plug in an XLR.

“The Scarlett 2i2 has no “Mic/line” switch – the Focusrite preamp stage is automatically configured for a microphone when you plug an XLR into the input, and for a line or instrument when you connect a jack plug.”

Focusrite Scarlett User Guide


Understanding the different types of inputs on your audio interface—mic, line, and instrument—will maximize the potential of your recording setup. Each type of input is designed to handle specific audio sources and signal levels, and using the right one can greatly enhance the quality of your recordings. 

Whether you’re recording vocals with a microphone, a guitar directly, or connecting a synthesizer, it’s all about matching the right source with the right input. 

And while the technical details may seem daunting at first, with a bit of knowledge and practice, you’ll be able to navigate your audio interface like a pro. So plug in, dial in your settings, and let your creativity flow—the perfect recording awaits.

Leave a Comment