October 2024: Fractal Audio's VP4 Virtual Pedalboard has been added to the wiki.

Multiplexer block

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Available on which products

  • Axe-Fx III: 2 blocks
  • FM3: ?
  • Axe-Fx II: no
  • FX8: no
  • AX8: no

Channels or X/Y switching

  • Axe-Fx III: 6 channels
  • FM3: ?
  • Axe-Fx II: n/a
  • FX8: n/a
  • AX8: n/a

What does the Multiplexer do

The Multiplexer block (MUX) is a routing and switching tool. It allows on-the-fly switching between either rows on the grid (as long as you have them connected), or physical inputs (Input blocks on the grid aren't required), or USB. Or you can use its Bypass to switch between just two things.

Note that only one input can be active at a time. For multiple inputs, use the Mixer block.

No gap is heard when switching sources, because the MUX crossfades between sources very quickly.

"If you want cross-fades between amps you would use two amps and the new Multiplexer block which cross-fades between input sources. You can set the input source to be any row or physical input." source

The MUX can't be bypassed.

Multiplexer in Wikipedia

How to switch between sources

Simply bypassing and engaging the MUX disables and enables its routing. This only allows you to switch between two sources. Note that bypassing the MUX will sum all inputs, which may have an impact on the signal level.

More control is possible by making use of its Channels (with or without switching scenes). Six channels let you switch between 6 rows.

Also, a modifier can be attached to the Input Select switch, which lets you use a switch or pedal to select the input source.

Example of using the MUX to switch a pedal between operating as a Wah and as a Whammy

Parameters table

Parameter Axe-Fx III / FM3? Axe-Fx II AX8, FX8
Input Select yes - -
Input Mode yes - -