Connect your playback devices, such as turntables or CD players to the mixer using stereo cables and the "audio-in" ports on the back of the mixer.
Plug the mixer into the digital audio interface using the "line-out" port on the mixer and the "line-in" port on the interface.
Connect the interface to your computer if you plan on using software-based scratching and sound effects utilities. Although hardware processors can be used in conjunction with your mixer and playback devices, the ability to access and utilize several different tools at once on the computer makes software programs very advantageous.
Connect the audio interface to your computer using a serial bus interface cable. Although serial bus interface is the predominant data transfer method for audio interfaces, your interface may utilize USB (Universal Serial Bus) connections. If this is the case, connect the interface to the USB port on your computer using the USB cable.
Connect the MIDI (Musical Instrument Digital Interface) controller to your computer using a USB cable. This device will allow you to directly control any sound effects you wish to use within your mix.
Open your preferred DJ software program and select the audio interface as the desired input device within the program's settings. The software program will now receive audio directly from your playback devices.
Select the MIDI controller as your preferred MIDI input signal within the MIDI I/O (input/output) settings panel of your DJ software. The software will assign your device a specific channel number that you will use to program sound effects.
Load or install your desired scratching and effects plug-ins into your DJ software. Select the effects or scratching utilities that you would like to use and allocate them to individual pads or jog wheels on your MIDI controller using the channel assignment function.
Connect the audio interface to your speakers or amplifiers using a line cable. Test the connection on your devices by initiating playback on one of your turntables or CD players and activating the scratch wheel or MIDI effects pads. These programmed effects should directly alter sounds coming from your original playback devices.