lauke-lux
Fractal Fanatic
This fooled me more than once on the III think that is a great point to include.
This fooled me more than once on the III think that is a great point to include.
Wait...what is a modeler?The topic of setting and monitoring levels in the Axe-Fx III and FM3 has confused me in the past. Writing an article about it has been on my to-do list for quite a while. So here it is. It covers what's useful to know, for me. Answering some of my own questions. It may answer some of yours.
I may have gotten some details wrong. No doubt members of the community will jump in. Maybe Fractal Audio will. Consider this a work in progress. After having reached a stable condition (the article, not me), I'll move it to the wiki.
About LEVELS in the Axe-Fx III and FM3
The Axe-Fx III and FM3 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
DIGITAL AUDIO INPUT
- The signal from the guitar enters the hardware through the instrument input. The first parameter in the Axe-Fx III that matters, is found here: Setup : I/O : Input. The A/D Input 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 Input Level 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 - the red INPUT LED lights up occasionally (“tickle the 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 input parameter for the loudest one, and leave it there. Even when hitting red, the signal is never really clipping hard. There’s 6 dB of headroom, and then a soft-limiter kicks in.
- IMPORTANT! The A/D Input Level / Input Pad parameters do NOT have an impact on volume, tone or the amount of amp gain. That’s because the processor compensates the selected setting. BUT: do not set it below 5% on the Axe-Fx III.
- 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) now arrives in the so-called digital domain.
INPUT 1 GAIN
- Setup : I/O : USB/AES provides level controls for signal entering the processor through USB channels, and on the 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.
PRESET: INPUT BLOCK
- The Axe-Fx III provides a parameter to adjust ALL presets for variations in guitar output level (guitar pickups). It’s 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 an impact on blocks such as the virtual amplifier.
- The FM3 doesn't provide this parameter.
PRESET: AMP BLOCK
- 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.
PRESET: MORE ABOUT BLOCKS
- 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 have an impact on the gain or tone of the virtual amplifier.
- The Amp block also has a parameter that controls the level of the signal at the input: 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
PRESET: OUTPUT BLOCK
- When you select a block on the hardware and press Edit, you’ll see a mini meter, indicating the left/right input signal, and left/right output signal. 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. 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.
PRESET: LEVEL METERS
- The signal exits the layout grid through an Output block. I’ve stated above that the Amp Level parameter is the main parameter to control the overall preset level, but 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. 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.
GLOBAL EQ
- As written above, the Output blocks on the grid show vertical meters that display the preset output level.
- The same meters, but now displayed horizontally, appear when looking at the Layout screen in “zoomed out” view. They 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.
NOMINAL OUTPUT LEVEL
- 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.
HARDWARE OUT KNOBS
- 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. The legacy Axe-Fx II is set to +4 dBu at default, so it is louder than the III at factory settings.
DOWNSTREAM GEAR
- Finally, the OUT knobs on the hardware let you adjust the overall volume for each pair of outputs. This happens after the digital-to-analog conversion, so these are analog controls. 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.
- The OUTPUT LEDs on the Axe-Fx III correspond with the OUT knobs (post-fader). They can be seen as “levels into converters”. The FM3 has a single red CLIP LED instead.
- Output clipping depends on two things: (1) the preset output level and (2) the position of the OUT knob.
- If the meters indicate output clipping, action should be taken. Page right on the Layout screen, and check which block shows red output meters. For a quick temporary solution, turn down level in the Global EQ. Note that 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 22 dBu.
- When using AustinBuddy’s presets, take note of his specific advice to match output levels with a DAW.
I/O LOOPS
- Powered monitors, amplifiers etc. provide levels controls of their own. This is beyond the scope of this article.
A FINAL WORD
- 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. To achieve this, turn the corresponding OUT knob fully clockwise.
- 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.
It's a big collection of obscure Cold War era electronic parts all contained in a heavy wooden box, which tries to replicate the sound of (one) of the amps in a Helix, Kemper, or AxeFx. Due to issues like manufacturing tolerances, many of these "modelers" don't really sound like the ones in the AxeFx but some people swear that they're really close.Wait...what is a modeler?
These two statements seem to be contradictive.
- Finally, the OUT knobs on the hardware let you adjust the overall volume for each pair of outputs. This happens after the digital-to-analog conversion, so these are analog controls. 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.
- The OUTPUT LEDs on the Axe-Fx III correspond with the OUT knobs (post-fader). They can be seen as “levels into converters”. The FM3 has a single red CLIP LED instead.
- Output clipping depends on two things: (1) the preset output level and (2) the position of the OUT knob.
OK, but then this statement
Finally, the OUT knobs on the hardware let you adjust the overall volume for each pair of outputs. This happens after the digital-to-analog conversion ...
is incorrect. The output knobs is digital scaling before the digital-to-analog conversion.
That's not how I'm understanding the quoted post from Cliff. These sentences in particular:I don't think so. The output knobs control analog circuitry, after the D/A converter, IIRC.
Seems like the gain is applied before the converters, as otherwise it would have no influence on the signal clipping, right? Furthermore, it's stated that the meters show levels into the converters, so the fact that the meters change when you turn the knob seems to be another indication that the knobs operate in the digital domain.A signal is generated internally. [...] That signal is then multiplied by the "gain" of the output level knob (0 to 1). [...] If, after applying that gain, the signal exceeds 1.0 the converters will clip and red LEDs on the meters will light.
PRESET: MORE ABOUT BLOCKS
- When you select a block on the hardware and press Edit, you’ll see a mini meter, indicating the left/right input signal, and left/right output signal. 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. 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.
I also found some of those modelers are really expensive, especially compared to the original.A couple of issues that come up with these is that if you want to own "models" of a number of amps you need a very large room to keep them in, soundproofing to not disturb your wife, kids, or neighbors, and you can't really take a lot of them to a local pub gig although if you're happy with just one then you can "get by." They're also really heavy and you need to figure in the expense of employing a "roadie" to help you move them around, or a "chiropractor" to help you recover.
I'm far from an expert on this but I don't think the input level matters for an IR.I often observe that bypassing the Cab block increases level quite a bit in my presets, and have wondered if I'm compromising something somehow by using the amp block level knob for preset levelling as these adjustments are varying the Cab block input level more or less randomly - am I changing the intensity of the cab block model, or of the amp speaker page parameters by making overall level adjustments using amp block level.