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Amp and Cab modeling for beginners

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Preamps and power amps

Most traditional guitar amplifiers consist of a preamp and a power amp. The preamp is responsible for tone and gain, the power amp makes things loud and may add some distortion and character of its own to the sound.

The Axe-Fx series and AX8 model both: they provide "virtual" guitar preamps and power amps, combined in Amplifier models. Many heads, combos and racked preamps have been modeled.

The processors also provide many other effects, they can "reamp" a recorded dry signal, create Tone Matches of real amps and recordings (Axe-Fx only), capture Impulse Responses (Axe-Fx only), and more.

More about the Amp block...

Traditional guitar speaker (with power amp) or full-range amplification (FRFR)

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An amp, whether real or virtual, needs a speaker to sound good. And amplification is required to make modeling loud . Usually this means using either a traditional guitar cab with a power amp, or a so-called FRFR monitor.

- Traditional guitar cab and power amp

A traditional guitar speaker will give you the familiar and fairly easy to set up "amp in the room tone". This does limit possibilities, because any sound you will create will be colored by the character of the guitar speaker. When using a traditional cabinet, the preset doesn't need to contain a Cabinet model. If it does, disable it or disable Cabinet Modeling in the processor's setup menu.

To feed the guitar speaker, a hardware power amp is required.

This can be a guitar-oriented power amp, head or combo, which will add it own coloring to the sound and decreases the possible tonal variations. This usually sounds best with Power Amp Modeling disabled in the processor's setup menus.

More popular is a so-called "neutral" power amp, which neutrally amplifies the incoming signal into the guitar cabinet. This relies on the virtual power amp, so keep Power Amp Modeling enabled in the setup menu.


Alternatively, you can opt for FRFR sound reproduction and amplification: Full Range Flat Response. This requires a FRFR speaker and an external or built-in neutral power amp. Studio monitors are FRFR by nature, as well as some monitor wedges and cabs, high-quality PA-systems, and headphones.

FRFR systems and direct recording require Cabinet Modeling because the signal doesn't go through a traditional guitar cab. The Axe-Fx and AX8 have many built-in cabinet models. They also allow loading additional cabs from disk, known as Impulse Responses (IRs).

Important: when listening to an FRFR sound system with cabinet modeling, you're be listening to the sound of a miked speaker. That's a different tone than that of a guitar speaker cabinet. A virtual cab (almost always) represents the sound of a speaker that was captured using one or more microphones placed very close to the speaker (referred to as "nearfield" or "close-miking"). The sound of a guitar speaker at a certain distance is referred to as "far-field". Because of the close proximity of the recording mic to the speaker, the FRFR sound has more highs and lows, and has the characteristics of the microphone baked in. It can take a while to get accustomed to the FRFR sound, but realize it's the same tone you hear at a concert or when listening to recorded music.

Cutting through the mix

Important in general, but especially when playing through FRFR amplification: Fletcher-Munson curve. This is the scientific name for the fact that human ears perceive sound at low volume levels differently than at higher levels. At low volume levels people often turn up treble and bass. The "Loudness" switch on older home stereo systems does just that. At higher levels those controls need to be turned down to prevent harsh and boomy tones and to prevent the guitar from getting lost in the mix (a guitar that competes with cymbals and bass guitar will always loose that battle), turning up the volume won't help. So always dial in your live guitar tones at gig levels, and remember that the guitar is a "mid frequency" instrument.

Preventing clipping

Input clipping is not the same as output clipping.

It's okay for the Input LED to "tickle" the red. If it happens all the time, adjust Input Level or Input Pad in the I/O menu. Be aware that this control is NOT a gain control, it controls the signal-to-noise ratio only and does NOT affect signal level, amp gain or tone.

The Output LED indicates that the signal level in the effects chain is too hot for the digital-to-analog converter at the end. Adjusting the Input Level will NOT solve this. Decrease the level somewhere in the chain, preferably using Level in the Amp block, or in the Output block.

More about Levels.

Avoiding parameter paralysis

The sheer number of parameters and possibilities within the Amp and Cab blocks can dazzle the beginner. Therefore it's handy to have a reference tone. The Band-Commander (clean tone) and Friedman HBE (dirty tone) amp models at completely default settings, combined with stock cabinet #103 at default settings, provide a great reference.