The 32Classic MS comes with 9 pin "Sum Link" ribbon cable jumpers that can be used to connect the summing bus from one unit to the next via the rear 9 pin D connectors. The 32Classic MS also comes with a "Bus Link" cable that is used on the last unit in the stack to jumper the summing bus to the bus input effectively making the last unit the mix bus master of the change.
How do I use the built-in mixer?
Once the Sum Link and Bus Link cables have been connected across multiple units, each unit can send to the mix bus by pressing the MIX switch. Us the FADER to adjust the level to the mix bus or send to the bus at 0dB by pressing the 0dB switch. Use the PAN controls to adjust the left right positioning of the signal in the mix.
What does the MIX OUT knob do?
The MIX OUT knob is used on the last unit in the stack to control the final level of the combined mix from the various units.