Fractal AXE-FX II Quick Reference Manual
AXE-FX II
Amp & Cab
Quick Reference Guide
for Axe-Edit
Amp and cab block parameters explained
Amp and cab descriptions
Amp speaker types matched with Axe-Fx cabs
Tone stack seings
Drive block descriptions
Amp and cab block diagrams
content compiled from the Axe-Fx II manual, Wiki and forum
suggestions, corrections, etc.: send a PM to JMA at the Fractal Audio forum
rmware v10.06 ~ Axe-Edit v1.9 ~ rev. June 9, 2013
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DRIVE – Sets the preamp gain for more or less preamp distortion. Used in conjunction with MASTER, it determines whether the sound will be clean, slightly
broken up, moderately overdriven, or completely distorted.
BOOST – Toggles the input boost for an additional 12 dB of input gain. Enabling
Boost sometimes works better than turning up preamp gain.
BASS/MID/TREB – “Passive” tone stack. Can be changed with TONESTACK TYPE.
In most cases, DRIVE, BASS, MID, and TREB are accurate to within 10% of the
actual amp.
COMPRESSION – Most models default to zero as they do not have measureable
compression. Other models have a non-zero default value which matches the
amp’s preamp compression characteristics. The time constant of the dynamics can be set with PREAMP DYN TIME. Preamp compression can be used to
emphasize pick attack which is useful for certain musical styles.
PRESENCE – Boosts/cuts upper frequencies from the power amp by varying
negative feedback frequency response. Increased presence can help sound cut
through a heavy mix. Decrease it to compensate for overly-bright amps. Presence is tightly coupled to speaker impedance (HI FREQ, HI RESONANCE).
HI CUT – On amps with no negative feedback (DAMPING=0), PRESENCE is
replaced with HI CUT, a simple high-shelf EQ at the power amp output.
DEPTH – Boosts low frequencies from the power amp by varying the negative
feedback frequency response. On amps with a xed depth circuit, Depth will
have a preset value. Also called “Resonance” or “Girth” on some amps.
MASTER VOL – Determines the amount of power amp distortion. As it increases,
the tone controls have less inuence on the sound. Amp models default to a
starting Master Volume setting when selected. (Non-MV amps default to 10.)
Before adjusting the MASTER VOL, be aware that it defaults to 10 for nonmaster volume (vintage) amps. If you want more MV, increases the MV TRIM.
INPUT TRIM – A clean, linear gain applied at the input to the amp block that
adjusts the relative gain of the preamp. It does the same thing as the BOOST
switch, the dierence being that you can control how much is boosted or cut
(±20 dB). As a rule of thumb, every 2x multiplier equals +6dB boost. In other
words, Input Trim at 4.0 produces a +12dB boost.
You can also adjust preamp gain globally with GLOBAL AMP GAIN, which
aects every amp and preset. One reason you might do this is to compensate
for the gain dierence when switching to a hotter/ quieter guitar.
On the Axe-Fx unit: GLOBAL button > CONFIG > AMP GAIN
INPUT SELECT – The Amp block processes audio in mono. This control determines how incoming stereo signals will be processed.
FAT – Emphasizes midrange “body” by shifting down the tonestack center
frequency. Specically, it alters the tonestack treble capacitor, so the eect
depends on the tonestack’s location (see TONE page).
BRIGHT – A “treble peaker” which functions mainly to compensate for the loss
of highs at low amp volume. The eect may be subtle or quite pronounced,
depending on the amp selected, and it is also aected by the BRIGHT CAP.
SATURATION – Switches in a zener diode clipping stage between the preamp
and the tone stack (the “Arrendondo Mod”) for more aggressive distortion character which also adds compression and cuts volume. You may have to adjust
the MASTER or LEVEL to compensate.
MASTER VOL TRIM – Can be used to increase (or decrease) the Master Volume
for non-MV amps. If MV is 10 and you set MV Trim to 2.0 then the MV will be 20.
DYNAMIC PRESENCE – Models the output transformer leakage inductance that
results in a brightening of the tone when the power amp is pushed. Increasing
this value results in a brighter response as the virtual power amp is pushed.
When playing softly or at lower gains, the inuence of this control is lessened.
Note that this only aects the power amp modeling and is dependent on
the degree of power amp overdrive. This control can also be set negative to
cause the tone to darken when playing hard. This control can also be used to
help “dial in” the sweet spot of an amp model. As the MV is increased an amp
becomes more liquid, compressed and easier to play. However, the highs may
get overly compressed causing the amp to sound too dark. The Dynamic Presence control allows you to get the desired power amp drive and liquid feeling
and then bring the highs back without aecting the rest of the spectrum.
DYNAMIC DEPTH – Analogous to the Dynamic Presence control, this increases
or decreases low frequencies when the virtual amp is being pushed. While real
amps don’t display this behavior, it is a valuable tone-shaping tool.
Amp Block
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LOW RES FREQ/RES Q/RESONANCE – Guitar loudspeakers have a low-frequency
resonance, typically about 100 Hz. This shifts up slightly when the speaker
is mounted in an enclosure and is typically lower for open back cabs. This
resonance causes an increase in the power amplier response due to the nite
output impedance of the power amp. The default LF Resonance is based on the
cab most likely to be used with that amp.
HI FREQ – Sets the “corner frequency” of the speaker impedance rise due to
voice-coil inductance. The speaker voice-coil presents an inductive load to the
power amp at high frequencies. This inductive load, in conjunction with the
output transformer capacitance, creates a high-frequency resonance. Typical
guitar speakers have a corner frequency between 1 kHz and 2 kHz. Lower
values give more midrange emphasis.
HI RESONANCE – Similar to HI FREQ but this control only changes the slope
of the resonance. Default value is consistent with typical “semi-inductance”
of speaker voice-coil. Varying this value will change the high-frequency load
presented to the power tubes.
XFORMER LOW/HIGH FREQ – These set the output transformer bandwidth.
SPEAKER DRIVE – Simulates distortion caused by pushing a speaker too far. It
interacts with the MASTER.
NOTE: The SPEAKER page is not an EQ. It allows you to adjust the impedance
that the virtual speaker presents to the virtual power tubes. In most cases,
the resulting EQ is quite dierent than the impedance curve since negative feedback attens the response. If you turn DAMPING all the way down
then the EQ will be close to the impedance curve (but still inuenced by the
transformer).
Amp Block
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SUPPLY SAG – Controls power supply impedance. Higher settings simulate
higher power supply impedance, causing greater tube plate voltage (B+)
“droop” and giving a more compressed, spongy and looser feel. Sag interacts
with the MASTER: as the power amp is pushed and draws more current from its
power supply, Sag has more eect. Sag values around 2 simulate a solid-state
rectier, 4-6 a tube rectier.
Setting SUPPLY SAG to 0 disables the power amp and turns the MASTER into
a simple level control with a 40 dB range.
DYNAMICS – Simulates the interaction and compressive eects of the power
amp, power supply and speaker when they are pushed hard. Negative values
cause dynamic range expansion, while positive values cause dynamic range
reduction, resulting in a more compressive, bouncier eect.
DYNAMICS TIME – Controls how fast it happens.
In general, the more heavily driven the power amp section is, the more eect
the SUPPLY SAG and DYNAMICS controls have.
THUNK – Allows adding “weight” to tones by simulating the very low-frequency
interaction of a speaker cabinet with the guitar. Higher values simulate closer
proximity of the guitar to the cabinet.
PREAMP DYN TIME – The time constant of the dynamics, works with COMP.
PREAMP BIAS – Controls the bias point of the last triode (cathode follower not
counted) in the preamp. Depending on the bias points of the previous stages
increasing or decreasing this value can alter both the harmonic content and the
attack characteristics. Typically, if the previous stage has a negative bias then
increasing this value will be more noticeable and vice-versa.
TREMOLO FREQ/DEPTH (bias tremolo) – Works by varying the bias of the virtual
power tubes, resulting in a particularly “organic” sound. Most importantly, the
tremolo is “self-ducking” and decreases at higher signal amplitudes. On some
amps high values of bias trem depth can result in excessive crossover distortion. On others, the tremolo can vary greatly between loud and soft playing.
BIAS EXCURSION – GRID MODELING parameter that controls how much the
power tube grid voltage droops when the grids conduct.
EXCURSION/RECOVERY TIME – GRID MODELING parameter that controls the
time constants associated with BIAS EXCURSION.
XFORMER DRIVE – Sets the amount of core saturation in the output transformer, controling how hard the transformer is driven. Higher values simulate a
smaller, more easily saturated transformer.
XFORMER MATCH – One of the most powerful controls in the amp block. It
changes the turns ratio (and therefore the primary impedance) of the output
transformer, which controls how easily power tubes are driven into clipping.
Decreasing causes the power tubes to clip later, the phase inverter and grid
clipping become more predominant, and the speaker resonance will be more
pronounced. This control has more inuence with higher MASTER values and
low gain amps and less inuence with highly compressed amps. Increase
MASTER until desired amount of power amp distortion is achieved, then adjust
XFormer Match for sound’s character: higher = more compressed, lower = more
open. The LF/HF RESONANCE parameters interact strongly with this parameter.
B+ TIME CONSTANT – Associated with SUPPLY SAG. Controls rate of change in
power tube plate supply. “B+” refers to one of the high voltage “taps” or outputs
of the main power transformer. Lower values give a bouncier feel, while higher
values give a tighter, more aggressive feel. The eect of lower B+ is equivalent
to increasing XFORMER MATCH. A lower B+ means the plates clip sooner which
is the same as increasing the turns ratio on the transformer. This is assuming
that you rebias since typically lower the B+ aects the bias.
PICK ATTACK – Controls a sophisticated dynamic range processor that operates
on leading edge transients. Negative values reduce pick attack while positive
values enhance it.
Ghost notes are the result of a 120Hz signal plus harmonics getting past the
power supply ltering. High SUPPLY SAG along with low B+ TIME CONSTANT
can cause “ghost notes” when POWER SUPPLY TYPE is AC (as in a real amp).
Lower B+ Time Constant values will make the amp feel “faster” but too low
can cause ghost notes.
To hear what ghosts notes sound like, try the following: take an amp like
Plexi 100W, turn the SAG up and the B+ TIME CONSTANT down, then play
single notes around the 5th fret on the G string. You should hear a tone
unrelated to the pitched note.
Amp Block
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POWER TUBE TYPE – Allows selecting Tetrode (i.e. 6L6, KT66, etc.) or Pentode
(i.e. EL34, 6BQ5, etc.) power tube types. The type defaults to the appropriate
value when a model is chosen but may be overridden by the user.
POWER TUBE BIAS – Sets the bias point of the power amp. Increase Power Tube
Bias to decrease crossover distortion and vice-versa. Lower values approach
pure Class-B operation. Higher values approach pure Class-A.
DAMPING – Controls the amount of negative feedback in the power amp. The
feedback decreases output impedance, causing the amp to react less to the
speakers (”damping”). Higher values give a brighter, tighter, punchier sound but
can be harsh at very high MASTER levels. Lower values give a smoother, loose
and gritty sound and feel.
Setting DAMPING to 0 disables negative feedback and replaces the
PRESENCE control with HI CUT. DEPTH is also disabled since it only aects
negative feedback.
POWER SUPPLY TYPE – When set to AC, models AC rectication and resulting
supply ripple. High SUPPLY SAG along with low B+ TIME CONSTANT can cause
“ghost notes” when the supply type is AC (as in a real amp). Lower B+ Time Constant values will make the amp feel “faster” but too low can cause ghost notes.
AC LINE FREQ – Selects the line frequency.
MV LOCATION – Location of the Master Volume.
PRE-PI – Before the phaser inverter (most amps).
POST-PI – After the phase inverter (AC types).
PRE-TRIODE – Amp types based on Hiwatt models.
GRID MODELING – Replicates grid conduction in the preamp and power amp
stages, which adds “real world” high frequency “zz” or “grit”. Turn it o if this
eect is undesirable. Grid modeling parameters include BIAS EXCURSION and
EXCURSION/RECOVERY TIME.
TRIODE1/2 PLATE FREQ – Sets the cuto frequency of the plate impedance for
the next-to-last (triode 1) and last (triode 2) triode in the chain, which allows
you to control the buzziness that sometimes occurs with higher gain settings.
The capacitor across the triode’s plate resistor is used to smooth the response
and reduce noise. You can adjust the amount of capacitance, and the resulting
frequency. Lowering the frequencies dials out sharpness and “zz”, making the
tone smoother.
TRIODE HARDNESS – Controls how sharply the triodes enter saturation and can
be used to simulate softer/harder tubes. The eect is subtle and most apparent
at edge of breakup. Lower values give softer saturation, higher values give
a more aggressive breakup. Defaults to an appropriate value when an amp
model is selected.
PRESENCE FREQ – Alters the center frequency of the amp’s PRESENCE control.
DEPTH FREQ – Alters the center frequency of the amp’s DEPTH control.
POWER AMP LOW/HI CUT – Low/high pass lters placed after the power amp
section that shape the tonal color of the power amp. Note that AMP VOICING
also sets these values. Reduce Hi Cut to remove unwanted “zz”.
Amp Block
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DEFINITION – A basic “tilt EQ” located at the amp input. It changes the fundamental character of the amp from vintage to modern or vice-versa. Positive
values increase the amount of upper overtone saturation, negative values
reinforce lower harmonics.
LOW CUT – Reduces the amount of low frequency (10-1000Hz) before the
preamp input. Use this is to tighten up a tubby bass end. Somewhere between
10-150Hz is generally where it will sound best for standard guitar tones.
HIGH CUT – Reduces the amount of high frequency (2k-20kHz) after the
preamp output. Lower the value to make your top end sound smooth and silky,
raise it to make it brilliant and dened.
BRIGHT CAP – Sets the value of the capacitor which determines the sonic eect
of the BRIGHT switch. Increase to make the preamp brighter and vice-versa.
AMP VOICING – Voices the amp to a variety of tonal styles. Choose “Neutral” for
the raw amp sound or one of the other voicings for a quick “mix-ready” tone.
Aects POWER AMP LOW/HI CUT values and applies some parametric EQ.
When an amp is selected, the settings on this page are updated accordingly.
If you then select a dierent tone stack, the settings remain unchanged.
See the Tone Stack Settings table.
TONESTACK TYPES
BROWNFACE – warm Fender early 60’s sounds (Vibroverb)
BLACKFACE – crisp Fender late 60’s sounds (Twin Reverb)
BASSGUY – fat and gain-y Fender Tweed Bassman
TOP BOOST – AC30 Top Boost, warm and chimey
PLEXI – classic rock late 60’s Marshall, fat, dense gain
BOUTIQUE – Matchless, brilliant and crisp
HI POWER – Hiwatt, which had a very unique tonestack design, clean/
punchy
USA NORMAL – Mesa Boogie “Mark” series, warm, smooth gain
USA FAT –
RECTO ORG/RED – Boogie Rectiers
SKYLINE – Dumble amps had a specially voiced tonestack after the mid-‘80s
called “Skyliner”
GERMAN – dark-voiced stack for mega-gain amps
BLUES JR – modern Fender 1x10 combo
WRECKER – the late Ken Fisher’s legendary “Trainwreck” amp
VINTAGE – a mid-heavy stack great for fat, small tweed amp-type sounds
CA3+SE – Bob Bradshaw’s CAE preamps
FREYER D60 – VHT/Fryette
CHARACTER/FREQ – These two parameters control powerful “inverse homomorphic lters”. When playing softly this dynamic lter has little eect on
the sound. As the amount of distortion increases, the inuence of the lter
increases. The Character Frequency control sets the center frequency of
the lter while the Character control sets how pronounced the eect is. For
example, to darken the tone when playing harder, one might set the frequency
to 10 kHz and the amount to -5. Setting the amount to +5 will make the tone
brighter when playing hard. (Default = 0.)
TONE FREQ – Sets the center frequency of the tone controls. This control works
whether you are using PASSIVE, ACTIVE, or substitute tone stacks.
TONE LOCATION
PRE – Places the tone stack at the input to the preamp.
POST – Places it between the preamp and power amp.
MID – Places it between the last two triode stages.
END – Places it after the power amp (which is impossible with a real amp).
The farther upstream you position the stack, the thinner the sound.
MID will sound chunkiest, with END being rather dark.
TONESTACK TYPE
PASSIVE – Matches the tonestack with the selected amp type.
ACTIVE – Gives each tone control ±12 dB boost/cut making them more
sensitive; they also will not interact with each other.
AMP TYPE – Replaces the default tonestack with one from another amp.
USE MIMIC – Identies deviations in the response of the simulated amplier to
the actual amplier and generates corrective data bringing a level of accuracy
that has been heretofore unachievable.
LAST UPDATE: FIRMWARE v7
MR Z 38 SR – Doctor Z
EURO UBER – Bogner Uberschall, the loudest, most hi-gain tonestack
PVH 6160 – Peavey 5150
SOLO 100 – Soldano SLO
CORNCOB – British-made Cornford amp
EURO – Bogner Ecstacy
CAROLANN – Alan Phillip’s boutique masterpiece, tons of mids, hi-gain
CITRUS – modern Orange Rockerverb, classic rock gain with tons of mids
BRIT JM45 – Marshall JTM45, Marshall’s 1st amp model. fat and sweet
USA RHY – Mesa Boogie MKIV
RECTO NEW ORG/RED – Boogie Rectiers
SHIVER CLN – Bogner Shiva
CAMERON – Mark Cameron amp model
GERMAN V4 – Diezel VH4
BRIT JVM OD2 – Marshall JVM410
5153 GREEN/BLUE/RED – EVH 5150 III
BRIT SUPER – Marshall AFD100
DIV13 CJ – Divided by 13 CJ11
BADGER – Suhr Badger
Amp Block
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CAB – Loads a cabinet impulse response (IR). The older FAS and RW cabs were
recorded with neutral mics. OH, Kalthallen, and the Mix/Producer Pack series
have matching mics included in the IR.
CAB SIZE (MONO CAB ONLY) – “Scales” the IR to simulate shrinking or enlarging
of the speaker. This eect can be used to shift where the tone sits in a mix, or to
create dramatic eects. Subtle settings (0.9-1.1) will sound most natural.
MOTOR DRIVE – Models the eect of high power levels on speaker tone.
Simulates the impedance and distortion eects that occur when the speaker is
pushed hard. Be aware this setting adds a little compression as you increase it.
NOTE: This parameter appears on the ROOM page for stereo cabs.
MIC – Don’t feel that you have to add a mic unless you want to add EQ, which
is basically what you would be doing.
LOW/HIGH CUT – Adjusts the cuto point of rst order low/high pass lters.
Increase the Low Cut if the sound is too “bassy” or “boomy.” Decrease the High
Cut for a darker cab tone. Common settings are 80-150 Hz for high pass, and
5-7 kHz for low pass.
PROXIMITY – Causes an increase in bass or low frequency response as proximity
is increased (closer to speaker). Disabled when MIC is set to none.
DELAY – Delays the signal up to 1 second. With cab in stereo mode or with
two cab blocks in parallel, delaying one cab relative to the other can achieve
interesting comb lter eects. A common practice in studio recording is to use
multiple mics on a speaker at dierent distances to intentionally introduce it.
The eect is most pronounced when the cabs are summed to mono.
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ROOM LEVEL/SIZE – Determines the level and size of room reverb that is built
into the cab block. Increase to add room ambience to the sound.
MIC SPACING – Increases delay times inside the room reverb by simlating the
distance of the room microphone from the sound source.
AIR - Mixes some of the signal going into the Cab block with the signal leaving
the Cab block.
AIR FREQUENCY – Sets the cuto frequency of the mixed signal. Increase to
maximum value for a straight mix.
MOTOR DRIVE – See above.
EFFECT TYPE
MONO HIRES – mono processing at 2048 resolution (42ms).
MONO LORES – mono processing at 1024 resolution (21ms).
STEREO – stereo processing at low resolution (2 × 1024).
Note that with the stock cabs there is no signicant energy beyond an IR length of 1024. (The high res of 2048
allows for 1024 in stereo.) A mono cab with a non-acoustic IR would typically use Mono Lores (which also uses
less CPU).
LINK (STEREO ONLY) – Sets the left channel parameters as master controls, which set identical values for left
and right. You can still set right channel values independently.
MIC TYPES
57 DYN – Shure SM57
58 DYN – Shure SM58
421 DYN – Sennheiser MD 421 II
87A COND – Shure Beta 87A
U87 COND – Neumann U87
E609 DYN – Sennheiser e609 Silver
RE16 DYN – Electro-Voice RE16
R121 COND – Royer Labs R-121
D112 DYN – AKG D112
67 COND – Neumann U67
Cab Block