Fractal Axe-Fx II Quick Reference Manual

Quick Reference Guide for Axe-Edit Amp and cab block parameters explained Amp and cab descriptions Recommended speaker type for each amp Cliff’s Gain Controls Guide Drive block descriptions CC assigments sorted by function & CC content compiled from the Axe-Fx II manual, Wiki and forum suggestions, corrections, etc.: send a PM to JMA at the Fractal Audio forum firmware v19.00 ~ Axe-Edit v3.2.0 ~ rev. June 21, 2015

to the input jack. In many cases it has a bright cap so the frequency response will be dependent on the knob position. As the gain increases the tone shifts from a treble and upper mid emphasis to a bass and lower mid emphasis. On jumpered amps, this setting’s label changes to TREBLE DRIVE. OVERDRIVE – A second drive control for some amp models. It does not have a bright cap so it only affects the gain. Set Overdrive to 8.00 to get the identical response to pre-v10.10 firmware for models that have Overdrive. On jumpered amps, this setting’s label changes to NORMAL DRIVE. INPUT TRIM – A clean, linear gain applied at the input to the amp block that adjusts the relative gain of the preamp. (This is analogous to changing the type of tube for V1 in an actual amp.) It does the same thing as the BOOST switch, the difference 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. Input Trim should be set to 1.00 if you want to match the actual amp. BOOST – Toggles the input boost for an additional 12 dB of input gain. Enabling Boost sometimes works better than turning up INPUT TRIM. CUT – Reduces the amount of low frequencies into the amp. This can be used to achieve a tighter tone or to reduce low-end “flub”. This is similar to increasing LOW CUT (Tone page) while still retaining some low end so it doesn’t get thin. Provides an easy way to cut the overpowering bass in models such as Recto, Splawn Nitro, Komet and others. FAT – Emphasizes midrange “body” by shifting down the tone stack center frequency. Specifically, it multiplies the tone stack treble capacitor by four. Depending upon the type of tone stack, tone control settings, position, etc., the effect can be more or less noticeable. (See TONE page.) BRIGHT SWITCH – A “treble peaker” which functions mainly to compensate for the loss of highs at low amp volume. The effect may be subtle or pronounced, depending on the amp selected, and it is also affected by the BRIGHT CAP. 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 influence of this control is lessened. Note that this only affects 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 affecting 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. 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. Amp Block You can also adjust preamp gain globally with GLOBAL AMP GAIN, which affects every amp and preset. One reason you might do this is to compensate for the gain difference when switching to a hotter/­quieter guitar. On the Axe-Fx unit: GLOBAL button > CONFIG > AMP GAIN DYNAMIC PRESENCE/DEPTH are distortion-sensitive. The more the waveform distorts (the harder you play) the more pronounced the depth or presence boost/cut. If you play lightly (assuming you aren’t using stupid amounts of gain) the controls won’t seem to do much. As you play harder the effect becomes greater. MASTER VOLUME defaults to 10 for non-master volume (vintage) amps. If you want more MV on non-MV amps, increase MASTER VOL TRIM. Most MV amps achieve full volume between 2-4. Further increase compresses the bass and treble, thereby adding mids. (Bass and treble are boosted by the speaker impedance curve, so they clip earlier.) The sweet spot is that point at which the power amp starts to compress. If you want a more “open” sound, be careful not to set the MV too high. You can also lower XFORMER MATCH (a little goes a long way). You can increase LEVEL to compensate for low MV. Cliff: The way I dial in the MV is to turn it up until the amp stops getting louder. This is the point at which the power amp is saturating heavily. Then I back it off until I get the right amount of preamp and power amp distortion. That’s the sweet spot where you get the tone and the dynamics. Too little MV and it’s all preamp distortion and there’s not much dynamics. Too much MV and the power amp is clipping too much and it can get flubby and/or harsh. PRESENCE and DEPTH differ from BASS, TREBLE, and BRIGHT (Tone page) in that they are applied to the power amp as opposed to the preamp. Their effect is dependent on the amount of NEGATIVE FEEDBACK. For most tone stacks, when you set the BASS and TREB to zero, the tone stack becomes basically “flat” and the MID becomes a volume control. INPUT DRIVE and OVERDRIVE will have a dramatic effect on the response of the amplifier and the personality of your instrument. TOP ROW BOTTOM ROW PRESENCE – Decreases high frequency negative feedback in the power amp. Increased Increase it to help sound cut through a heavy mix. Decrease it to compensate for overly-bright amps. It is tightly coupled to speaker impedance (HI FREQ, HI RESONANCE.) HI CUT – On amps with no negative feedback (NEG FDBK=0), Presence is replaced with Hi Cut, a simple high-shelf EQ at the power amp output. (Hi Cut control is non-fuctional in Suhr models.) DEPTH – Boosts low frequencies from the power amp by varying the negative feedback frequency response. Amps with a fixed depth circuit have a preset value. Amps with no depth circuit default to zero (Fenders, most Marshalls, and generally most older designs). Also called “Resonance” or “Girth” on some amps. NOTE: Depth is non-functional on most of the USA amp models due to the unique topology of their feedback networks. MASTER VOLUME – Determines the amount of power amp distortion. As it increases, the tone controls have less influence on the sound. Amp models default to a starting Master Volume setting when selected. BASS/MID/TREB – “Passive” tone stack. Can be changed with TONESTACK TYPE.

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 amplifier response due to the finite output impedance of the power amp. The default LF Resonance is based on the cab most likely to be used with that amp. The Low Resonance parameter can be used to increase or decrease the amount of “thunk” or “knock”. 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 FREQ SLOPE – Allows fine adjustment of the high-frequency impedance of the virtual voice coil (which affects the slope of the impedance curve). Reducing the Slope simulates a speaker that is less inductive, increasing Slope simulates a speaker that is more inductive. Typical speakers range from 3.0 to 4.5 with the median being about 3.7. Lower values yield greater midrange while higher values are more scooped and sizzly. 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. The SPEAKER page is not an EQ. It allows you to adjust the impedance that the virtual speaker presents to the virtual power tubes. For a guitar amp with no negative feedback, the voltage frequency response of the power amp will very closely match this since the power amp is basically a current source. For a guitar amp with negative feedback, the resulting EQ is quite different than the impedance curve since negative feedback flattens the response. If you turn NEG FDBK all the way down then the EQ will be close to the impedance curve (but still influenced by the transformer.) Don’t be afraid to turn LOW RESONANCE close to 10. In fact, some Celestion and Eminence speakers are equivalent to about 8-9 on LOW RESONANCE. This will increase the interaction between the power tubes and the speaker load. XFORMER LOW/HIGH FREQ – These set the output transformer bandwidth. 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. You also reduce the power tube compression of the lows and highs. This control has more influence with higher MASTER values and low gain amps and less influence 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. 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. SPEAKER DRIVE – Simulates distortion caused by pushing a speaker too far. It interacts with the MASTER. Amp Block TOP ROW BOTTOM ROW Use XFORMER MATCH to intentionally mismatch speaker impedance in order to get a different tone. To simulate plugging an 8-ohm speaker into a 4-ohm jack, set it to 2.0. For the other way around, set it to 0.5.

compression threshold of the cathode follower. Many models default to zero as they do not have measureable compression. CRUNCH – Makes things more crunchy. It controls the distortion texture when you hit a note or chord. DYNAMICS – Controls a dynamics processor that can be used to alter the dynamic response of the amp algorithms. When set below zero the amp compresses resulting in a smoother, less dynamic sound. When set greater than zero the amp expands resulting in a punchier, crunchier and more dynamic sound. Note that extreme values can have undesirable side-effects such as pumping and clipping. OUTPUT COMP2 – Leveling compressor (think LA-2A) specifically tailored to reduce the output dynamic range of the Amp block. It can also be used to simulate the compression you get from a dynamic microphone and/or some mic preamps. The parameter value is the compression ratio, which equals 1 + 3 * comp / 10. Attack and release are fixed. COMP TYPE2 – Sets the mode of the Amp block’s output compressor: OUTPUT – The previous type where the compressor acts on the output of the block. FEEDBACK – Also compresses the block output but applies dynamics to the input of the block based on the output compression. COMP THRESHOLD2 – Sets the level at which OUTPUT COMP reduces the amplitude of the audio signal when that level is exceeded. COMP CLARITY2 – Adjusts the bass response of the input dynamics and can be used to add clarity to the bass. 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 effect. Sag values around 2 simulate a solid-state rectifier, 4-6 a tube rectifier. PREAMP SAG – OFF replicates the behavior of separate preamp and power amp. ON replicates the behavior of an integrated tube head or combo amp. 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 effect 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+ affects 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. CATHODE TIME1 – Sets the attack time of the compressor. CATHODE RATIO1 – Sets the maximum amount of compression, with lower values giving more compression. The cathode “squish” modeling algorithm improves the feel of cathode-biased power amp models (Class-A, Mr Z, etc.) It has two adjustable parameters: CATHODE SQUISH – Sets the amount of bias shift due to cathode voltage rise. (Zero defeats the cathode squish modeling.) SQUISH TIME – Sets the time constant of the cathode network. 1 cathode follower algorithm parameter 2 amp block output compressor parameter Amp Block In general, the more heavily driven the power amp section is, the more effect the SUPPLY SAG has. Setting SUPPLY SAG to 0 disables the power amp and turns the MASTER into a simple level control with a 40 dB range. Ghost notes are the result of a 120Hz signal plus harmonics getting past the power supply filtering. 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. TOP ROW BOTTOM ROW

the Presence knob (USA LEAD and USA RHYTHM). When engaged, it normalizes the amount of high frequencies produced in the power section. PRESENCE will be more effective and will act on a higher frequency range. Note that it may result in volume reduction since the negative feedback is increased which lowers the loop gain. 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 TUBE TYPE – Selects a specific power tube type and sets DYNAMIC DAMPING. This doesn’t change the sound in the same way actually changing tubes would because it only changes the distortion curves, not the transconductance. In real amps, an EL34 has more than twice the transconductance of a 6L6. This means the plate current will be twice as great for a given grid voltage. This makes EL34s sound “more midrangey” and 6L6s sound “tighter’”or “fuller”. DYNAMIC DAMPING – Adjusts the plate characteristics. Defaults to the appropriate value when an amp model or power tube type is selected. POWER TUBE BIAS – Sets the quiescent operating current of the virtual power tubes. Increase it to reduce crossover distortion and vice-versa. Lower values approach pure Class-B operation. Higher values approach pure Class-A. NEGATIVE FEEDBACK – 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. TRIODE1/2 PLATE FREQ – Sets the cutoff 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 “fizz”, making the tone smoother. (Also see HIGH CUT FREQ to reduce “fizz”.) 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. If you are right on the edge of breakup the triode hardness is very powerful as it controls the harmonic series. Higher values will cause the overtone series to have a less steep decay and will increase perceived “sparkle”. Together with PREAMP BIAS you can control how chimey and “round” the tone is. PWR AMP BIAS – Controls the amount of power tube mismatch by adjusting the offset voltage of the virtual power amp. A value of zero produces nearly symmetrical clipping which will produce very little even harmonics. Higher values will produce increasingly asymmetrical clipping which increases the amount of even harmonics. Small amounts of even harmonics can make the power amp distortion sound “warmer” and more bell-like while higher amounts will give a “fuzzier” tone. PWR AMP HARDNESS – Controls the hardness of the virtual power tube grid clipping. The default value is determined by the tube type. Example: amp models that use EL84 tubes will have a default power amp hardness of 2. MV LOCATION – Location of the Master Volume. PRE-PI – Before the phaser inverter (most amps). POST-PI – After the phase inverter (AC types). This causes the PI to clip before the grids (if the MV is less than full). This creates a very aggressive and open sound. PRE-TRIODE – Amp types based on Hiwatt models. Setting NEGATIVE FEEDBACK to 0 disables negative feedback and replaces the PRESENCE control with HI CUT. DEPTH is also disabled since it only affects negative feedback. POST-PI MV turns a lot of mid-gain amps into ripping monsters. The only caveat is that, like a real amp, the more you turn the MV down the less effective Presence and Depth become (since the loop gain is reduced). Adjusting PWR AMP HARDNESS is often not noticeable because negative feedback around the power amp makes the distortion harder. You can make the power amp distortion softer by reducing NEGATIVE FEEDBACK. Increase POWER TUBE BIAS to thicken clean tones; reduce it to add aggres- sion to high-gain sounds. A value of 0.5 or so will run the virtual tubes at around 75% of full power and clean tones will sound warmer but you will lose that sizzle on high-gain tones. Amp Block TOP ROW BOTTOM ROW