Mono and stereo signal

The information on this page supplements the official manuals.

Mono or stereo

Effects sound gloriously in stereo. However, when it comes to FOH sound, stereo separation may not translate very well to a live audience. People seldom are in the right spot to hear both sides equally well. Discussion.

Setting output to stereo

To get sound in stereo:

• the preset must contain at least one stereo effect, and
• the signal is not summed to mono before entering the output section, and
• the device must be set to stereo output in the I/O menu, and
• Left/Right outputs must both be connected to a stereo audio system.

When connecting the left and right outputs of the AX8 or Axe-Fx to a mixer, make sure that the two channel strips are hard-panned to the left and right.

Setting output to mono

To get mono sound:

• sum the signal on the grid to mono

OR

• set Output Mode in the I/O menu to one of the mono settings: "Sum L+R" or "Copy L>R"

OR

• connect only the left or right output to the amplification system or mixer.

"Sum L+R" means that the left and right signal are mixed together. Be aware that this may cause phasing issues.

"Copy L>R" means that the left side signal is copied to the right side (the original right signal is gone). This will defeat effects such as Ping-Pong delay, which is is based on hard-panned signals.

Outputs 1 and 2 each can be configured separately.

More information: I/O connections and levels.

Effect blocks and mono/stereo output

Flanger, Chorus and Phaser are mono by default. Use the parameter LFO Phase to switch to stereo.

Everything before an Amp block or Drive block will always be summed to mono. To keep a stereo signal before the Amp block stereo, use two Amp blocks (not supported on the AX8), and adjust Input Select and Balance to make each block handle one side of the signal.

When placing a Cab block at the end of the grid, the output signal will be summed to mono, unless the Cab is set to Stereo mode or when using two panned mono Cab blocks in parallel. When a Cab block is set to Stereo mode but followed by a mono effect such as Drive, the resulting signal will also be summed to mono.

Stereo Enhancer

Read this: Enhancer block.

Panner effect

The Panner effect (Tremolo/Panner) pans the signal left and right, just like a ping pong delay.

Phase cancellation and comb filtering

• Phase cancellation: when two 100% identical audio signals of opposite phase are merged, the result is complete silence.
• Comb filtering: summing two identical audio signals with one slightly delayed, makes a tone sound hollow, thin and glassy.

You need to be careful of phase cancellation and comb filtering when summing a stereo signal (preset) to mono, if it contains effects which invert phase or shift time alignment.

"Hollowness means phase cancellation which typically arises from collapsing to mono somewhere or somehow having the same signal slightly delayed added in somewhere." source

More information:

• SAE Online: Mono Compatibility and Phase Cancellation.
• Universal Audio: Understanding Audio Phase and Correcting Issues.

When running your rig in mono:

• Don't use the Enhancer (ENH) block in Classic Mode.
• Don't use Phase Reverse in the Delay block.
• Use Output Mode Copy L > R instead of Sum L+R in the Global menu.
• Don't use Micro Delay in the CAB block.
• Avoid Chorus types such as "80s" and "Triangle".