Fractal AXE-FX II Quick reference manual - page 7
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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.
SATURATION SWITCH – 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.
AUTH – replicates authentic saturation circuit behavior and lowers the
volume out of the virtual preamp.
IDEAL – replicates the idealized behavior from firmware v14.xx and earlier.
SATURATION DRIVE – Controls the amount of saturation.
INPUT SELECT – The Amp block processes audio in mono. This control
determines how incoming stereo signals will be processed.
USE MIMIC – Identifies deviations in the response of the simulated amplifier to
the actual amplifier and generates corrective data bringing a level of accuracy
that has been heretofore unachievable.
MODELING MODE – Varies between “realistic” and “idealized” preamp and
power amp modeling.
AUTHENTIC – Replicates a tube amplifier with the utmost accuracy.
SMOOTH – Sets Triode Hardness to the minimum value essentially creating
an ideal preamp and turns off grid conduction modeling in the power amp.
This removes most of the “nasty” distortion that tube amps create.
IDEAL – Removes most of the “warts” from the modeling which includes
grid conduction, output transformer distortion, bias shifting, and AC power
supply modeling. Supply sag, screen voltage effects, and crossover distortion
are still modeled.
IDEAL/SMOOTH – Same as Smooth, except it also sets Triode Hardness to
its lowest value. This is in essence an ideal preamp plus an ideal power amp.
PREAMP TUBE TYPE – Be aware that the difference between these selections is
very subtle and you may not be able to tell them apart.
SHORT PLATE – An accurate model of a modern “short plate” production
12AX7.
LONG PLATE – An accurate model of a classic “long plate” 12AX7.
MODERN – An idealized 12AX7 model. This is the same model from version
18.04 firmware. This model is useful for high gain tones that can benefit from
the increased clarity and string separation.
VINTAGE – Another idealized 12AX7 model also from version 18.04
firmware. It has a softer breakup than the Modern model and is useful for
“vintage” tones where more base nonlinearity is present.
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 (the
ratio of even/odd harmonics) and the attack characteristics. The further you
move away from (roughly) zero the more even harmonics are introduced. It’s
an asymmetric transfer function so you have to experiment. Typically, if the
previous stage has a negative bias then increasing this value will be more
noticeable and vice-versa. Use with PREAMP HARDNESS.
PREAMP HARDNESS – Controls how sharply the triodes enter saturation and
can be used to simulate softer/harder tubes. The effect is subtle and most
apparent at edge of breakup. Lower values give softer saturation and will
sound softer (naturally) but have less note separation. Preamp Hardness at zero
gives a smoother distortion with reduced upper harmonics. Higher values give
a more aggressive breakup and better note separation.
ADDITIONAL NOTES ON MODELING MODE
The audibility of these settings is dependent upon the particular amp model
and various parameters. The use of these modes in conjunction with other
parameters can yield idealized tones not achievable with real tube amps.
AUTHENTIC duplicates the previous behavior of the deprecated Grid
Modeling* parameter.
When IDEAL is chosen, the global Modeling Version parameter is irrelevant.
* Grid modeling replicates grid conduction in the preamp and power amp
stages, which adds “real world” high frequency “fizz” or “grit”. Grid modeling
parameters include BIAS EXCURSION and EXCURSION/RECOVERY TIME.
Amp Block
The primary controls that adjust saturation behavior are PREAMP TUBE TYPE
(Other page), PREAMP BIAS and PREAMP HARDNESS (Dynamics page).
SATURATION changes the distortion character. To preserve the distortion
character and tone use BOOST or INPUT TRIM instead.
AC LINE FREQ – Selects the line frequency.
POWER TYPE – When set to AC, models AC rectification 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.
VARIAC – AC voltage control that sets the relative AC line voltage into the
amp simulation implementing a virtual “Variac”. Note that normally the
volume would vary with the Variac setting in a real amp but the simulation
compensates for the volume change by applying the inverse. This mitigates
having to manually compensate using the Output Level.