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The topic of setting and monitoring levels in the Axe-Fx III and FM3 has confused me in the past. Writing an article has been on my to-do list for quite a while. So here it is. It covers what's useful to know, answering some of my own questions. It may answer some of yours.
About LEVELS in the Axe-Fx III, FM3, FM9
The devices provide parameters at various places that control the level of the signal directly, as well as meters that display levels visually. This applies to the hardware and software. This document explains them, following the flow of the signal.
HARDWARE A/D INPUT LEVELS
About LEVELS in the Axe-Fx III, FM3, FM9
The devices provide parameters at various places that control the level of the signal directly, as well as meters that display levels visually. This applies to the hardware and software. This document explains them, following the flow of the signal.
HARDWARE A/D INPUT LEVELS
- The guitar's output signal enters the hardware through the instrument input. The first Axe-Fx III parameter that matters, is found here: Setup : I/O : Input. The A/D Sensitivity Levels parameters control the signal going into the analog-to-digital converter. Setting it right makes sure that minimal undesirable noise will enter the processor (aka signal-to-noise ratio or SNR).
- The FM3 does not have these parameters. Instead, it provides Setup : I/O : Audio : Input Pad parameters.
- The INPUT LEDs on the hardware correspond with these parameters.
- Setting the A/D Input Level / Input Pad parameters correctly means that - ideally - there's no clipping warning and the meter doesn't go red. It’s common for a guitar not to hit red at all, which is nothing to worry about. If you have multiple guitars, just set the parameter for the loudest one, and leave it there. There’s 6 dB of headroom when the red LED lits, and 0.5 dB left when the clipping warning appears, then a soft-limiter kicks in. IMPORTANT! The A/D Input Level / Input Pad parameters do NOT affect volume, tone or the amount of amp gain. That’s because the processor compensates.
- When you page right from the Home menu, you reach the Meters page. The ANALOG IN meters show the same thing as the INPUT LEDs on the hardware, without the green / orange / red colors.
- After the A/D conversion, the signal (the note or chord you struck on your guitar) is now in the so-called digital domain.
- Setup : I/O : USB/AES provides level controls for signal entering the processor through USB channels and (Axe-Fx III only) SPDIF and AES. Check these if you're connected to a computer and you get no sound from your DAW, YouTube, etc.
- The Axe-Fx III provides a parameter to adjust ALL presets for variations in guitar output level: Setup : I/O : Input : Input 1 Gain. It trims the level of Input 1 before the start of the grid so, unlike the A/D Input Level parameters, it has affects blocks such as the virtual amplifier.
- The FM3 doesn't provide this parameter.
- The signal enters the layout grid through an Input block. Like all blocks on the grid, it has a level parameter and 4 channels. This parameter lends itself well to adjust the signal for differences between guitars per preset, as an alternative to the global Input 1 Gain parameter mentioned above.
- When it comes to levels, the Amp block on the grid is special. People often use the Amp Level parameter to set the overall level of the preset. This parameter controls the output of the Amp block and therefore does not affect the gain or tone of the virtual amplifier.
- The Amp block also has a level parameter at the input of the Amp block: Input Trim. It can be used to mimic the difference between the Low and High inputs on a real amplifier, or to control the virtual amplifier’s gain (instead of using Input Drive in the Amp block).
- There's much more to the Amp block, like Master Volume, but that's beyond the scope of this article. More information
- When you select a block on the hardware and press Edit, you’ll see a mini meter, indicating the left/right input resp. output signals. The software editors do not provide these mini meters. If the input mini meter hits red, it means that the output level of the preceding block is too hot. Blocks in the digital domain can’t really clip though; that can only happen at the final digital-to-analog conversion stage.
- Page right on the Layout screen to reach the Meters page (not the same as the Meters page on the Home screen), and you’ll see those mini meters for the entire grid. These are very handy to detect the cause of routing or level problems!
- It’s good practice to aim for unity gain where possible, meaning that engaging and bypassing a block should not cause the sound to get softer or louder, unless that’s the goal.
- The signal exits the layout grid through an Output block. While the Amp Level parameter is the main parameter to control the overall preset level, Output Level can also be used as such. Especially because it provides additional functionality.
- First, it lets you set individual output levels for each of the 8 scenes of the preset. Handy if you prefer to use dedicated scenes for soloing and such, but note that changing the output levels of individual scenes also affects the level of reverb and delay trails when switching between scenes, which may be undesirable.
- Also, it provides meters that display the very important preset output level.
- As written above, the Output blocks on the grid show vertical meters that display the final preset output level.
- The same meters, but now displayed horizontally, appear when looking at the Layout screen in “zoomed out” view. These are often referred to as VU meters which show the relative loudness of the preset.
- The software editors show the same meters in the Preset Leveling window.
- These meters, which all show the same thing, can be used to set and match the levels of presets for consistent sound. Ideally, the level of the preset should hover around the red lines in the meters. The VU meters are calibrated such that there is still 12 dB of headroom at the red line with the OUT knob (see below) at maximum.
- Each Global EQ, found in Setup : Global, includes a level parameter. This lets you control the overall level of the outgoing signal through that particular output port. This does not affect AES, SPDIF and USB Audio.
- Finally, the OUT knobs on the hardware let you adjust the overall volume for each pair of analog outputs. The exact position of the OUT knobs is shown as a percentage in Setup : Utility : ADC Levels.
- OUT 1 also controls the volume level of the headphones output.
- These knobs do not affect the USB Audio, SPDIF and AES output levels on the III. On the FM3, SPDIF is affected.
- The OUTPUT LEDs on the Axe-Fx III show the digital levels going into the D/A converters. The FM3 has a single red CLIP LED instead of meters.
- When the LED(s) indicates output clipping, there are two ways to intervene: (1) adjust the preset output level (on the grid or with the Global EQ level) or (2) turn down the OUT knob. Because together they set the level into the D/A converter. Note that output clipping can’t damage the device.
- When you page right from the Home menu, you reach the Meters page. The ANALOG OUTPUT meters show the same thing as the OUTPUT LEDs on the hardware, but without the green / orange / red colors.
- The maximum output level of the Axe-Fx III and FM3 is around 22 dBu.
- When using AustinBuddy’s presets, take note of his specific advice to match output levels with a DAW.
- Setup : Audio : Output Level lets you choose between -10 and +4. This is the overall nominal output level. The default is -10 dBv to reduce the number of support cases due to people overloading the inputs on consumer-grade interfaces, mixers, etc. Most professional gear runs at +4 dBu so you may want to change the level to +4 dBu in that case. Note: the legacy Axe-Fx II is set to +4 dBu at default, so it is louder than the III at factory settings.
- Powered monitors, amplifiers etc. provide levels controls of their own. This is beyond the scope of this article.
- I/O ports 3 and 4 on the Axe-Fx III, and I/O port 2 on the FM3, are designed for unity gain applications, such as effect loops. What comes in, goes out at the same level when the corresponding OUT knob is turned fully clockwise. This means that these output ports are less loud than OUT 1.
- A level parameter is just that. It makes the signal louder or softer. It's digital, it has no sound of its own, it's neutral. Changing the value of a block’s level parameter will only change the sound (gain, distortion, tone, etc.) when that block is followed by non-LTI effects such as an Amp or Drive block.
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