Always consult the official Owners Manuals and Guides first.
Content is currently being reviewed to make sure you have the most complete and up-to-date information

Amp and Cab modeling for beginners

From Fractal Audio Wiki
Revision as of 20:50, 1 April 2014 by Yek (talk | contribs)
Jump to navigation Jump to search


Virtual preamp

The Axe-Fx II (and XL) is a guitar preamp. It models more than hundred real amps such as heads, combos and racked preamps. You can also use its many other effects, use it to reamp a dry signal, create tone matches of real amps and recordings, use it for mastering, etc.

Virtual power amp

The Axe-Fx has built-in power amp simulation, which means that you can listen to the sounds of the modeled amps through headphones and neutral amplifiers, and connect the Axe-Fx to a mixer or record it without needing a separate power amp.

Using a real power amp

To amplify the Axe-Fx through a real speaker, you need a real power amp. Either a standalone tube power amp designed for guitar, a head or combo (through its effects loop), or a so-called neutral power amp.
You can also use studio monitors and monitor wedges with built-in amplifiers ("active", "powered").

Playing through a guitar speaker

You can use the Axe-Fx with a traditional guitar speaker, in combination with a power amp. This will give you the familiar amp-in-the-room tone. It does limit the possibilities of the Axe-Fx, because any sound you will create will go through that speaker and therefore will be colored by it.

Playing through FRFR amplification

You can opt for FRFR (Full Range Flat Response) sound reproduction. This requires a FRFR speaker and an external or built-in neutral (power) amp. Studio monitors are FRFR, as well as some wedges / cabs.
A FRFR setup requires power amp simulation and cabinet simulation to be engaged. Cabinet simulation means that the sound of a virtual speaker cabinet is added to the tone of the modeled amp. The Axe-Fx comes with many built-in cabinet models and allows loading external cab models, known as IRs or user cabs (Impulse Responses).

Listening to FRFR amplification

It's very important to realize that when you're using FRFR with cabinet simulation, you'll be listening to the sound of a mic'd speaker, as opposed to an amp-in-the-room. A cab model always represents the tone of a speaker that as captured using one or more microphones, mostly positioned very close to the speaker. That's totally different from listening to a guitar speaker at some distance. FRFR has more lows, more highs and has the coloring of the used microphone baked in. It takes a while to get accustomed to FRFR tone, but it's the tone the audience hears too through the FOH system and when listening to recorded music.

Being heard in the mix

Important in general but especially with digital modeling: the Fletcher-Munson curve. This is the scientific name for the fact that human ears perceive sound at low volume levels different than at higher levels. At low volume level people often turn up treble and bass. The Loudness switch on older home stereo systems does just that. At higher volume levels those controls need to be turned down again because, in a live environment, tones with too much treble and bass are prone to get lost in the mix. Otherwise the guitar will compete with cymbals with the bass. Even turning up the volume level often won't help. Remember that the guitar is a "mid frequency" instrument. So: dial in your live guitar tones at gig level.


Be aware that input clipping is something totally different than output clipping.
It's okay for the input LED to "tickle" the red. If it happens all the time, decrease Input Level the I/O menu. Be aware in this is not a real input level control, the control controls the signal-to-noise ratio only and does NOT affect signal level or gain.
The output clipping LED light indicates that the signal level in the effects chain is too hot. Adjusting Input Level does NOT solve this. Decrease the level somewhere in the chain.

Editing sounds

Read the Owner's Manual for editing instructions. It includes a 60-Second Edit Guide and an overview of shortcuts.


Axe-Edit — load and save presets from/to disk, edit sounds, rearrange presets and user cabs.
Fractal-Bot — backup or restore your Axe-Fx, load/save presets and user cabs, upgrade the firmware.
Cab-Lab — mix IRs and send them to the Axe-Fx, convert IRs, create an IR of your guitar cabinet (IR Capture).

Questions, issues?

Consult the Owner's Manual, delve into this wiki, read the Troubleshooting FAQ and visit the forum.

Have fun!