GAIN is applied after the INPUT and conversion to digital. So if you connect a turntable
or any other external device and your channel level meter is constantly moving  beyond
the four orange segments with the GAIN knob in center position, dial back that device's
output  level  until  only  the  loudest  passages  reach  the  orange  range  of  the  Input  level
meter.
4.4.1.2 FX Assign Buttons
 
Each  channel  offers  two  FX  Assign  buttons  which  activate  routing  through  TRAKTOR's  FX
Units. The left one routes the channel to FX Unit 1, the right one routes to FX Unit 2.
FX Assign Buttons
These assignments aren't mutually exclusive, so you can send signal to either one or both FX
Units at the same time.
If you activate both FX assign buttons, your track will first run through FX1, then FX2.
 
4.4.1.3 EQ Knobs
 
Each channel provides a 3-band EQ section: 
HI, MID and LOW knobs allow you to restore the
tonal balance between different tracks by increasing or decreasing the corresponding frequen-
cy band's volume.
Hardware Reference
The Mixer
 
TRAKTOR KONTROL S5 - Manual - 171