The M-Audio M-Track is a USB audio interface, allowing users to record audio using microphones and various instruments.
The M-Track has a multitude of connections, and which ones you use will depend on what instruments or equipment you are using with it.
To start, you will need to have the M-Track connected to the iMac using the supplied USB cable.
For playback and monitoring, the M-Track has stereo outputs on the rear panel. These will already be connected to the sound studio's powered monitor speakers. The output volume for the monitors is controlled by the large volume knob on the right side of the M-Track's front panel.
Alternatively, you can playback and monitor with headphones using the headphone jack on the front panel, to the left of the volume knob. This headphone jack is a 1/4" (6.35mm) jack. The sound studio has an adapter for converting a 3.5mm standard stereo plug into a 1/4" (6.35mm) plug. The headphone output has its own discrete volume control, a small knob located directly above the jack.
There is another control for the output as well, which is to the left of the headphone volume knob. This knob changes the monitor output, blending it anywhere between 100% direct monitoring (hearing exactly the signal that is entering the M-Track) and 100% USB output (hearing what the computer is sending back to the M-Track after any signal processing and effects, along with the rest of the mix).
The M-Track has two inputs that can accommodate a number of different input types. They are numbered 1 (the left input) and 2 (the right input). Each input has its own adjacent gain knob to adjust the input signal level and its own level meter on either side of the "M-Track" logo.
The number 1 (left) input can accept line-level signals (these come from powered instruments, such as keyboards, synthesizers, guitars and bass guitars with active pickups, and electronic drums) via a 1/4" (6.35mm) cable, or an XLR cable for a microphone.
The number 2 (right) input can accept line-level signals and XLR microphones as well. However, it can also be used to accept instrument signals, meaning any guitar or bass with passive pickups (most guitars and basses). To enable this feature, there is a small "LINE/INST" switch next to the gain knob for input 2. Pushing it down to "INST" turns on the preamplification for direct guitar input. This will be necessary when using Garageband's amp modelling features, unless your guitar has an active pickup.
Finally, many condenser microphones require 48V "phantom power" to work. There is a "+48V" button to the left of the headphone jack to turn phantom power on for both inputs. None of the Sound Studio's own microphones require phantom power. Unless you are certain that you are using a condenser microphone that requires it, leave phantom power switched off. For some microphones, such as ribbon microphones, turning phantom power on can actually damage them, so please be mindful of this setting.
Chapter 4: Getting real sounds into your Mac - This chapter discusses using an audio interface with Garageband, including both inputs and output, and gives an overview of different types of audio interfaces
Garageband ’11 Essential Training
Chapter 1: Connecting instruments, MIDI controllers, mics, audio interfaces, and speakers - This chapter helpfully explains the principles of an audio interface (such as the M-Audio MTrack), including what types of connections they offer, what you can use them with, and troubleshooting. Please note that this course deals with a previous version of iTunes.
Digital Audio Principles
This is an extremely in-depth course about recording digital audio, and includes sections about audio interfaces as well as cables, microphones, monitors, etc.