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Everything you've always wanted to know about LEVELS (III + FM3)

Rick

Fractal Fanatic
Very, very useful information. You are a major asset to the community here, and I surely appreciate your efforts!
 

Smittefar

Fractal Fanatic
I'm far from an expert on this but I don't think the input level matters for an IR.
One laymans explanation for IRs is to think of the output signal as the sum of playing the IR waveform at each sample (e.g. 48000 times a second at 48kHz), multiplied by the value of the original signal at that sample. Not sure how dumbed down that explanation is but if it's approximately correct then changing the level before the IR would just change the level of the output signal by the same value times a constant factor depending on the selected IR, and should not influence tone (except for the usual psychoacoustic effects from adjusting volume). Other things in the cab block such as the preamp could have a nonlinear response though, so it might make a difference if you touched those parameters.
You're right, applying the IR is a strictly linear operation, but the cab block has other functionalities, specifically preamp simulation and saturation, which is a non-linear operation, and those might change the sound when you increase the level going into the cab block.
 

yek

Moderator
Moderator
I managed to make a small experiment that made it clear to me that adjustments to Out 1 are applied in the digital domain before the D/A converters - the output LEDs reflect the level after the Out 1 scaling.

I pulled up a preset with no amp block, just a cab block with an acoustic sim IR. This is a preset, where I have always struggled with output clipping.

I put the looper in front and recorded a riff that produced output clipping. Then I recorded three passes in my DAW (reaper) using the analog output of the AxeIII. I lined up the recordings and normalized all the recordings to better see the clipping. You see the normalization gains encircled in red

Out 1 setting -10 dBV and knob all the way up. The waveform is clearly clipped at the two markers. The red circle shows that 10 dB was added to the clip to achieve peak normalization, so I was far away from clipping my analog inputs
  1. Out 1 setting -10 dBV and the knob at noon. Level is reduced by ~12 dB but (22 dB needed to achieve Peak normalization) - There is no clipping to be seen
  2. Out 1 setting +4dBu and the knob set to have the same level as pass 1 (10 dB needed for Peak Normalization) - There is no clipping to be seen.
Also, the red Output LEDs on the front panel did not light up during passes 2 and 3.

The OUT knob does indeed affect the digital signal level into the converters, which makes all easier to understand. A matter of interpretation. I edited the OP.
 

Philo

Member
Useful. FYI, the fifth bullet under hardware A/D input levels has a typo “have affect”.
presumably you onlh want one of these words.
 
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horror

Member
Great information, thanks for compiling. Admittedly I’ve ignored the hardware itself in favor of Axe Edit so the section on the meters page and levels across the blocks grid was really useful. Had no idea that existed.
 

Tommy Tempest

Power User
I prefer not to adjust the Out block volume to remove clipping or balancing presets. I leave it at "0". I prefer to adjust the level in the amp block.
Of course if there is no amp block, I would have to change the Out block setting.
 

Flashback

New Member
Thanks yek! This is a great guide, but I wonder how do you folks manage levels when recording?

When using the Axe-Fx III as an audio interface over USB, is there a way to lower the perceived output level of a preset without changing the level that is recorded into a DAW?

The problem I have is when recording songs in a DAW the output level of the song differs from the preset level, so the guitar is either too loud or too quiet while playing along. Adjusting the preset volume to match changes the level that is recorded. Setting it right for one song screws it up for another song.

Is there an easy way to manage the USB (DAW) output level separately from the Axe's guitar output level without using a separate interface? With the Out 1 knob controlling both simultaneously it's a bit tricky, or am I missing something?

Also, when you have two cabs panned left and right, muting one normalizes the volume of the other and makes it louder. Is there a way to disable that? When recording panned guitars I only want to hear the Axe out of one side, but without the volume increase. Panning the output block is what I've been doing but it's kind of an awkward way to go about it when you have to keep changing from left to right all the time.
 

unix-guy

Legend!
Thanks yek! This is a great guide, but I wonder how do you folks manage levels when recording?

When using the Axe-Fx III as an audio interface over USB, is there a way to lower the perceived output level of a preset without changing the level that is recorded into a DAW?

The problem I have is when recording songs in a DAW the output level of the song differs from the preset level, so the guitar is either too loud or too quiet while playing along. Adjusting the preset volume to match changes the level that is recorded. Setting it right for one song screws it up for another song.

Is there an easy way to manage the USB output level separately from the Axe's guitar output level without using a separate interface?

Also, when you have two cabs panned left and right, muting one normalizes the volume of the other and makes it louder. Is there a way to disable that? When recording panned guitars I only want to hear the Axe out of one side, but without the volume increase. Panning the output block is what I've been doing but it's kind of an awkward way to go about it when you have to keep changing from left to right all the time.
USB Return Levels in the global menu.
 

Smittefar

Fractal Fanatic
I prefer not to adjust the Out block volume to remove clipping or balancing presets. I leave it at "0". I prefer to adjust the level in the amp block.
Of course if there is no amp block, I would have to change the Out block setting.
Or the level knob in any other block. I have an always on filter block in all my presets, where I use a scene controller on the level to adjust the scene level
 

Jozsef Kiss

Inspired
Sorry in advance! - if I'm asking for stupidity!
I consider myself a practical person!
For historical reasons - I live in Hungary - it was not possible to buy a Fender, Marshall, Vox amplifier.
However, I managed to get the wiring diagrams from the mentioned amplifiers!
So, I only had one option! I built those amplifiers.
Therefore, I am trying to use the AX FX-III amplifiers with the circuit diagram in my head.
So far, I thought I knew everything about tube amps!
But now that I own the AX FX III, I feel like I don't know anything. So I feel totally stupid like I don't know anything about tube amps.
After this long introduction, would my request follow ?!
YEK - Everything you've always wanted to know about LEVELS
Would I have a big request for this tutorial?
Could this great writing be expanded by illustrating a conceptual circuit diagram?
I am thinking of such a schematic circuit diagram as the one I am enclosing here.
Sorry for the English!
I do not speak the language.
 

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yek

Moderator
Moderator
Yes, that’s possible but I can’t do it, sorry.

The Owners Manual already provides diagrams of many things.
 
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 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
  • 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 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 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 - 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 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 affect volume, tone or the amount of amp gain. That’s because the processor compensates. 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) is now in the so-called digital domain.
DIGITAL AUDIO INPUT
  • 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.
INPUT 1 GAIN
  • 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 an impact on blocks such as the virtual amplifier.
  • The FM3 doesn't provide this parameter.
PRESET: INPUT 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: AMP BLOCK
  • 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
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 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.
PRESET: OUTPUT BLOCK
  • 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.
PRESET: LEVEL METERS
  • 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.
GLOBAL EQ
  • 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
  • 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.
NOMINAL OUTPUT LEVEL
  • 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
  • Powered monitors, amplifiers etc. provide levels controls of their own. This is beyond the scope of this article.
I/O LOOPS
  • 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 FINAL WORD
  • 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.
Excellent work! Very helpful!
 

austinbuddy

Fractal Fanatic
Vendor
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 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.

OMG I can't LOVE this post enough, sorry I missed it until now.

THANK YOU so much Yek - this will really help a lot of users out, and I will be linking to it and spreading it far and wide!!!
 
Last edited:

maxolla

Inspired
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 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
  • 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 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 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 - 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 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 affect volume, tone or the amount of amp gain. That’s because the processor compensates. 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) is now in the so-called digital domain.
DIGITAL AUDIO INPUT
  • 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.
INPUT 1 GAIN
  • 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 an impact on blocks such as the virtual amplifier.
  • The FM3 doesn't provide this parameter.
PRESET: INPUT 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: AMP BLOCK
  • 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
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 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.
PRESET: OUTPUT BLOCK
  • 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.
PRESET: LEVEL METERS
  • 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.
GLOBAL EQ
  • 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
  • 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.
NOMINAL OUTPUT LEVEL
  • 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
  • Powered monitors, amplifiers etc. provide levels controls of their own. This is beyond the scope of this article.
I/O LOOPS
  • 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 FINAL WORD
  • 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.

Great little article. Now I know what all of those flashing lights mean! I wonder about the FX send and return. I'm having an intersting situation occur where setting the FX return level at 100% causing clipping in several delays, the most notable being the 2290. Everything else seems to sound fine but a couple of delay algorithms. Is there any procedures for getting the correct level at the send returns?

Thanks for writing this very informative post.
 
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