Always consult the Owners Manuals
From Axe-Fx II Wiki
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Gate: supported by which Fractal Audio products
- Axe-Fx III: 4x.
- Axe-Fx II: 2x.
- AX8: 1x.
- FX8: 2x.
Gate: X/Y switching or channels
- Axe-Fx III: 4 channels.
- Axe-Fx II XL and XL+: yes.
- Axe-Fx II Mk I and II: no.
- AX8: yes.
- FX8: yes.
There's no MIDI CC available for Gate/Expander X/Y switching on the Axe-Fx II.
In the Input block
Presets have a noise gate at their input. It uses CPU cycles, so switch it off (turn Threshold to Off) if you have no need for it in a preset.
(Axe-Fx III) "Each input block has a built-in gate." source
As a separate block
The Gate/Expander block provides more control, such as Sidechain Select, and flexibility.
About the noise gate
"I don't use the gate at all. On the Ultra I would use the gate on high gain patches but I find I don't need it now. I did some measurements and the II is at least 10 dB better SNR." source
"The self-noise of your guitar is usually greater than the self-noise of the Axe-Fx. This noise will be amplified by the amp block. For high-gain tones it is almost always necessary to use a gate to control this noise. Adjust the noise gate in In/Gte to squelch the noise." source
"There are noise "reduction" techniques but all alter the desired signal in some way. Noise gates are among the most useful for our particular needs. Digital cameras use various techniques based on the statistics of the image (i.e. if an area of the image is monochromatic heavier filtering is applied). The Intelligent gate in the Axe-Fx uses some crude statistical processing where the statistics are based on the typical stats of a typical guitar. IOW, noise reduction is destructive. You can't beat the laws of physics. So you can't remove noise without somehow altering the original signal." source
"The amp model doesn't add noise, it just amplifies it." source
"To get the best noise performance it is important that the Instr In trim is set correctly in the I/O > Input menu. Set this as high as possible without clipping the input." source
Noise gate as a Global Block (Axe-Fx II only)
Noise gate settings can be saved as a Global Block in the Axe-Fx II. This applies to the gate at the input and the Gate block.
More information in the Owner's Manual.
The gate features two types:
- Classic: basic downward expander.
- Intelligent: faster and more stable gating along with a proprietary noise reduction algorithm.
Attack and Release
"I prefer a fast attack and slow release and a ratio around 2." source
"For guitar I recommend setting the Attack time very short (less than 10ms) and the Release time to 100-200ms. Ratio 2-3:1 and Threshold to taste." source and source
"General rule of thumb on any gate is short attack time (<5ms) and long release time (~100ms)." source
"Typically you want a fast attack and slow release otherwise you'll get noise as the gate rapidly opens and closes when the signal decays." source
"A rule-of-thumb is that your release time should be 10-100 times the attack time." source
You can use SCSEL (SideChain Select) to select the signal the gate is working with. If the gate is the first block in the routing there's no need to use SCSEL. If the gate is placed after other blocks in the routing, it can be useful to use SCSEL to set an optimal source signal, such as Input 1. This is similar to the way the ISP Decimator operates. This is done by creating a separate routing from the grid input into the Gate block. source source source
SideChain Select is not available on the AX8.
Global noise gate offset
The Offset parameter in the Global menu offsets the gate threshold across all presets. This can be used to increase or decrease the threshold to compensate for varying interference levels. If the Threshold parameter in the preset is set to “Off”, the Global Offset will have no effect. The default value is 0 dB and is set to that upon System Reset.
"When I program a pro rig, we always set the noise gate at a threshold that feels best in the studio, knowing that the global NOISEGATE OFFSET which can save you in a pinch should the rig need to be used in a noisy environment. By the way, BEFORE we had this global option, we'd often opt for a much more aggressive threshold: -65 db or thereabouts!" source
Tips and tricks
Volume block as alternative to a noise gate
A different approach to keeping the noise low: try a Volume block with the Volume parameter tied to the Envelope controller. As long as you don't hit the strings, the (input) signal is off.