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

Difference between revisions of "Mono and stereo"

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From old Wiki:
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__TOC__
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=About mono and stereo output=
  
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Always discussion going on about this. The Axe-Fx sounds gloriously in stereo. However, that experience doesn't always translate very well to a live audience, because people seldom are in the right place to hear both sides equally well.  
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Effects sound gloriously in stereo. However, when it comes to FOH sound, stereo separation may not always translate well to a live audience. People seldom are in the right spot to hear both sides equally well. Also, many PA systems are mono.
  
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Use the I/O menu (> Audio) to select mono or stereo OUTPUT mode. The output mode affects the output signal only. The signal of a mono source can be transformed into a stereo signal by using certain effect blocks, or the other way around. These are the choices:
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From the [[Owners_Manuals|Axe-Fx III Owner's Manual]]:
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* “Stereo”: select this when going direct (no amplification) into a mixing table or when using stereo amplification
 
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* “Sum L+R”: use this to feed a mono device. The left and right channels are summed, so both channels are sent to a single mono output. While this seems perfect for mono output, there is a caveat: summing signals can cause phase cancellation. Example 1: if a preset contains an ENH block (Stereo Enhancer), this setting will make your tone glassy, thin and hollow. Example 2: if a preset contains a delay with Phase Rev (Advanced page) switched on, all delay trails will disappear. A lot of factory presets employ either the Stereo Enhancer or the delay with Phase Rev set to on!
 
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* “Copy L>R”: use this with a mono source. The signal of the left channel is copied to and replaces the right channel. A nice alternative for L+R Sum to avoid the phase cancellation issue. But you'll lose the right channel signal with hard-wired stereo effects such as Ping-Pong Delay. And you'll also lose cab(s) panned to the right side (when using a stereo cab or two separate cabs).
 
  
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The output mode applies to Output1 only. Output2 is always stereo. So what if you want to send the FOH a stereo signal, and a (summed) mono signal to feed your monitor? Solutions:
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* '''Stereo''' – No special settings required
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* Do it the other way around: set Output1 to mono (monitor) and use Output2 for a stereo signal to FOH. This means that you can't use the balanced XLR outputs for FOH.
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* '''Half-Stereo''' – Leaving the unit in its default stereo configuration but connecting only one (Left) output results in a “half‐stereo” setup. This works fine, aside from the exceptions such as ping-pong, panning, etc). No special settings required
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* Or: use Output1 for a stereo FOH signal. Feed your monitor thrugh Output2 using the FXL block. Force the signal into summed mono by placing a Filter or Volume of Mixer block before it, with both Pan controls set to center.
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* '''Dual Mono''' – Sonically, this is identical to half-stereo, with the same limitations, except that mono signal is produced at both the left and right jacks so you can connect to two monitors. To switch to dual mono, go to Setup > I/O > Audio and set Mode for the desired output to “COPY L->R”
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* '''Summed Mono''' – Left and right channels are added together resulting in an identical mono signal at both left and right outputs. This has the advantage of not discarding half of the sound, but summing has its own issues. For example, short delays or phase differences between channels can result in strange artifacts or even total cancellation. To switch to summed mono, Setup > I/O > Audio and set Output Mode for the desired output to “SUM L+R”
  
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Now about the effect blocks. Flanger, Chorus and Phaser are set to mono by default. Cliff: "All the effects, except the drive and amp blocks, are fully stereo. Many of the blocks default to a dual-mono configuration to prevent phasing problems when running into a mono PA." So everything before the Amp block or a Drive block will always be summed into mono.
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The VP4 also has a "Mono" input mode.
  
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old Wiki:
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Read <q>[[I/O connectivity and levels]]</q> for more information.
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Cliff: "All the effects, except the drive and amp blocks, are fully stereo. Many of the blocks default to a dual-mono configuration to prevent phasing problems when running into a mono PA." Effects such as Phaser, Chorus and Flanger can be stereo, but are mono by default. This is because a stereo configuration may cause phasing problems when the effect is placed before the (mono) amp sim. Use the parameter LFO Phase (value 90) to switch the effect to stereo.
 
  
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[[category:Connecting_to_a_monitor_or_amplifier]]
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A simple method to switch between mono and stereo, is to set one channel of the Cab block to Stereo and another channel to mono.
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[[category:Connecting to a computer or digital device]]
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[[category:Connecting to a mixer or headphones]]
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[[image:mono_stereo.jpg|link=|300px]]
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[[category:Presets]]
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=Stereo output requirements=
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For a stereo output signal:
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* The preset must contain at least one stereo effect, and
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* The signal is not summed to mono before entering the output section, and
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* The output mode of the device must be set to Stereo in the Setup menu, and
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* Left/Right outputs must both be connected to a stereo audio system.
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When connecting the left and right outputs of the processor to a mixer, make sure that the two channel strips are hard-panned to the left and right.
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Most [[Factory presets]] are designed for stereo output.
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=Mono output requirements=
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For a mono output signal:
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* Sum the signal on the grid to mono, or
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* Set Output Mode in the Setup menu to one of the mono settings: "Sum L+R" or "Copy L > R", or
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* Connect only the left or right output to the amplification system or mixer, or
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* Set the audio system to mono.
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=Effects: mono or stereo=
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Blocks such as Flanger, Chorus and Phaser are mono by default. Use the parameter LFO Phase to switch these to stereo.
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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 in parallel paths, if the device supports this, and adjust Input Select and Balance to make each block handle one side of the signal.
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When placing a Cab block at the end of the grid, the output signal will be summed to mono, unless the Cab is operating in stereo (stereo input and stereo output). When a Cab block is operating in stereo but followed by a mono effect such as Drive, the resulting signal will also be summed to mono.
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=Left is left, Right is right=
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If you want to make sure that Left=Left and Right=Right, just turn the Balance parameter in an engaged block on the grid to left and right.
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Or run the Ping Pong Delay: the first repeat should be heard through the LEFT channel.
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=Stereo Enhancer block=
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Read <q>[[Enhancer block]]</q> for more information.
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=Panner effect=
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The Panner effect ([[Tremolo/Panner block]]) pans the signal left and right, just like a ping pong delay.
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=Phase cancellation and comb filtering=
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; Phase cancellation : When two 100% identical audio signals of opposite phase are merged, the result is complete silence.
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; Comb filtering : Summing two identical audio signals with one slightly delayed, makes the sound hollow, thin and glassy.
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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.
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<blockquote>
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'''FRACTAL AUDIO QUOTES'''
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<HR>
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<blockquote>
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[http://forum.fractalaudio.com/threads/what-causes-hollowness-in-modeling.98515/#post-1182125]
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Hollowness means phase cancellation which typically arises from collapsing to mono somewhere or somehow having the same signal slightly delayed added in somewhere.
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</blockquote>
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</blockquote>
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To avoid phase cancellation when summing a stereo signal to mono:
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* Don't use the [[Enhancer block]] in Classic Mode.
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* Don't use Phase Reverse in the [[Delay block]].
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* Use Output Mode Copy L > R instead of Sum L+R in the Setup menu.
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For more information see:
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* SAE Online: <q>[http://www.audiocourses.com/?s=phase+cancellation Mono Compatibility and Phase Cancellation]</q>
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* Universal Audio: <q>[http://www.uaudio.com/blog/understanding-audio-phase Understanding Audio Phase and Correcting Issues]</q>
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=Videos=
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[[video:RoshMonoStereo]]
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[[category:Axe-Fx2]]
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[[category:Axe-Fx3]]
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[[category:AX8]]
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[[category:FM3]]
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[[category:FM9]]
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[[category:VP4]]
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[[category:FX8]]
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[[category:Sounds]]
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[[category:All]]

Latest revision as of 12:21, 1 November 2024

About mono and stereo output

Effects sound gloriously in stereo. However, when it comes to FOH sound, stereo separation may not always translate well to a live audience. People seldom are in the right spot to hear both sides equally well. Also, many PA systems are mono.

From the Axe-Fx III Owner's Manual:

  • Stereo – No special settings required
  • Half-Stereo – Leaving the unit in its default stereo configuration but connecting only one (Left) output results in a “half‐stereo” setup. This works fine, aside from the exceptions such as ping-pong, panning, etc). No special settings required
  • Dual Mono – Sonically, this is identical to half-stereo, with the same limitations, except that mono signal is produced at both the left and right jacks so you can connect to two monitors. To switch to dual mono, go to Setup > I/O > Audio and set Mode for the desired output to “COPY L->R”
  • Summed Mono – Left and right channels are added together resulting in an identical mono signal at both left and right outputs. This has the advantage of not discarding half of the sound, but summing has its own issues. For example, short delays or phase differences between channels can result in strange artifacts or even total cancellation. To switch to summed mono, Setup > I/O > Audio and set Output Mode for the desired output to “SUM L+R”

The VP4 also has a "Mono" input mode.

Read I/O connectivity and levels for more information.

A simple method to switch between mono and stereo, is to set one channel of the Cab block to Stereo and another channel to mono.

Mono stereo.jpg

Stereo output requirements

For a stereo output signal:

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

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

Most Factory presets are designed for stereo output.

Mono output requirements

For a mono output signal:

  • Sum the signal on the grid to mono, or
  • Set Output Mode in the Setup 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, or
  • Set the audio system to mono.

Effects: mono or stereo

Blocks such as Flanger, Chorus and Phaser are mono by default. Use the parameter LFO Phase to switch these 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 in parallel paths, if the device supports this, 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 operating in stereo (stereo input and stereo output). When a Cab block is operating in stereo but followed by a mono effect such as Drive, the resulting signal will also be summed to mono.

Left is left, Right is right

If you want to make sure that Left=Left and Right=Right, just turn the Balance parameter in an engaged block on the grid to left and right.

Or run the Ping Pong Delay: the first repeat should be heard through the LEFT channel.

Stereo Enhancer block

Read Enhancer block for more information.

Panner effect

The Panner effect (Tremolo/Panner block) 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 the 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.

FRACTAL AUDIO QUOTES

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

To avoid phase cancellation when summing a stereo signal to mono:

  • Don't use the Enhancer 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 Setup menu.

For more information see:

Videos

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