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Bose engineered the T8S ToneMatch mixer to have eight full-function channels and two Auxiliary inputs. The Aux inputs 9/10 are routed directly to the Main Output. You can use the Pan and Level adjustments accessible through the PAN/AUX menu. There are no changes to routing, or signal processing available.
The Aux inputs are useful for sources that have their own volume and signal processing (e.g. EQ or effects). They are similar to an effects return channel on other mixers. Use the Master Volume to raise and lower the volume of the Aux inputs in sync with the other channels. To change the volume of the Aux inputs relative to the other inputs you can use the AUX/PAN Level (soft menu), or on the source device.
If you want to add any signal processing (ToneMatch Presets, zEQ, ParaEQ, Effects or Reverb, you need to connect to one or two of the eight full-featured channels (one through eight).
For more information, please see:
T8S Aux Inputs