October 2024: Fractal Audio's VP4 Virtual Pedalboard has been added to the wiki.
Gate/Expander block
Contents
Available on which products
- Axe-Fx III: 4 blocks
- FM3: yes
- Axe-Fx II: 2 blocks
- AX8: 1 block
- FX8: 2 block
Channels or X/Y switching
- Axe-Fx III: 4 channels
- FM3: 4 channels
- Axe-Fx II XL and XL+: X/Y
- Axe-Fx II Mk I and II: no
- AX8: X/Y
- FX8: X/Y
There's no MIDI CC available for Gate/Expander X/Y switching on the Axe-Fx II.
Noise gate: at the input or later in the chain
Each preset has a noise gate at its input. It uses CPU cycles, so switch it off (turn Threshold to Off) if you have no need for it.
Axe-Fx III and FM3 — all signal that appears at an Input block is processed by the gate, whether analog, digital, or USB. The gate includes EMI filtering which helps suppressing pickup noise.
(Axe-Fx III) "The new noise gate in the Input block is killer. I recommend starting with default settings (reset the block) and then adjust the threshold to obtain the desired results." source
(Axe-Fx III) "Each input block has a built-in gate." source
There is also a separate, dedicated Gate/Expander block which allows precise control over gate settings, such as Sidechain Select, and more flexibility, because you can put anywhere on the grid. A common position is to add it after a high-gain Amp block.
Noise gate types
There are two types:
Classic – a basic downward expander
Intelligent – a faster and more stable gate, using a proprietary noise reduction algorithm
The Axe-Fx III and FM3 also include EMI filtering as part of the noise gate in the Input block.
(Axe-Fx III) "Improved Input block noise gate. When the Type is set to Intelligent (default) the noise gate now provides smart EMI filtering which reduces hum and buzz. NOTE: For best results the AC Line Frequency parameter in the Global Settings menu should be set to match the power line frequency of your country (i.e. 60 Hz for North America, 50 Hz for EU, etc.)."
Prior to Axe-Fx III:
"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
"The Intelligent mode of the gate is more than just a gate, it includes noise reduction." source
Parameters
Parameters table
| Parameter | Axe-Fx III / FM3 | Axe-Fx II | AX8, FX8 |
|---|---|---|---|
| Type (only in Input block) | yes | ||
| Threshold | yes | ||
| Ratio | yes | ||
| Attack Time | yes | ||
| Release Time | yes | ||
| Hold Time | yes | ||
| Sidechain Source | yes | ||
| Low Cut, High Cut | yes | ||
| Global > AC Line Frequency | yes | no | no |
Threshold
This determines how quiet the signal must be for the gate to close. See: Global Noise Gate Offset (below).
(Axe-Fx III) "The new noise gate in the Input block is killer. I recommend starting with default settings (reset the block) and then adjust the threshold to obtain the desired results." source
Note: the Threshold parameter on the Axe-Fx III (and FM3) is different from the Axe-Fx II.
"There is a 20 dB offset between the II and II." source
"-65 dB on AX8 = -45 dB on Axe-Fx III." source
Ratio
Determines how much quieter the signal will be when the gate is closed.
Attack and Release
Attack determines how long it takes for the gate to open after signal levels exceed the threshold. Keep this low to preserve the attack of first notes.
Release determines how long it takes for the gate to close. Use a slow setting for a gradual decay to prevent your notes from being clipped suddenly.
(Axe-Fx II) "I prefer a fast attack and slow release and a ratio around 2." source
(Axe-Fx II) "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 source
(Axe-Fx II) "General rule of thumb on any gate is short attack time (<5ms) and long release time (~100ms)." source
(Axe-Fx II) "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
On the Axe-Fx III always start with default settings. Don't set Attack and Release too fast.
Level
The Level parameter of the gate determines the loudness of the signal entering the grid. It still works when the gate is off and can be used to boost of cut signal strength.
Sidechain Select
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.
The Offset parameter in the Global menu offsets the Threshold setting 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
This helps the gate in the Input block to suppress EMI filtering. Set it to the correct frequency for your country.
This is not the same parameter as AC LINE FREQUENCY in the Amp block.
Not available on the Axe-Fx II, AX8 and FX8.
Volume block: alternative noise gate approach
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.
