T4S/T8S Aux Input Level Setting

Issue

The ToneMatch Mixer^[1] Aux inputs do not have trim controls or LEDs. How do I set the input levels to avoid clipping?

ToneMatch Mixer^[1] using Aux Inputs (4/5 on T4S ToneMatch mixer 9/10 on T8S ToneMatch mixer)

On the ToneMatch Mixer^[1] turn the Master Volume all the way off. You don't need an audible signal to set the input levels.
Connect the source to the ToneMatch Mixer^[1] Aux inputs.
Turn the source up to the maximum you will use during performance (as high as you can without audible distortion)
Set the Rotary Selector to PAN/AUX
Select Aux
Set the Levels to 75%
Turn the Rotary Selector to Prefs
Select Input Levels
Select Aux channels (right most knob under the display)
Play some music at your source
Check the input levels

As your signal varies, you will see the signal indicators move.
The vertical bar is the peak indicator
If the signal is near the far right AND the peak indicator is at or below the red dotted line, you have a good strong signal.
If the peak indicators are hitting the far right, you are clipping the input. Return to the PAN/AUX setting and turn down the Level