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Axe-Fx Firmware Version 21.00 Public Beta #3 (Beta 3)

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Fractal Audio Systems
[EDIT] Link removed due to bug in USA Lead models.

Bunch more amps verified. This version also fixes a bug in Beta #2 where bias points were being incorrectly calculated. This primarily affected high-gain amps and could result in them feeling "tubby". Several other bugs were also addressed.

Axe-Fx III Firmware Release Notes​


New “Cygnus X-2” amp modeling:

  • Improved Amp block output transformer algorithm. New algorithm more accurately models B-H curve resulting in a clearer low end. New algorithm now also accounts for effect of speaker impedance on transformer response.
  • Improved power tube modeling. This yields better dynamics, improved low frequency accuracy and more accurate interaction with output transformer.
  • Improved cathode follower algorithm. Provides more accurate “cleanup” when volume is rolled off.
  • Improved triode algorithm more accurately models plate bypass capacitors.
  • Various other improvements.
  • All amp models have been updated as a result of the aforementioned improvements.
The default values of various parameters have been updated. Existing presets are automatically updated to the new values upon load.

Improved Drive block modeling to more accurately model effects of op-amp finite open-loop gain and GBW product.

Added “Griddle Cake” Drive model based on a Crowther Hot Cake. The “XLF” switch on the pedal can be replicated by turning the Bass Response knob fully CW.

Added “Overdrive Volume” parameter to Dumble-type amp models (ODS-100, Two Stone, etc.). This is sometimes labeled “Ratio” or “Lead Master”. As the Master Volume on these amps often has a bright capacitor the Overdrive Volume control allows setting the Master Volume higher to counteract the bright cap and then lowering the power amp drive with the Volume.

Added “Plate Suppressor Diodes” parameter. This value is set automatically when the amp model is chosen but the user can override the default setting. Most amps do not have suppressor diodes but some do (e.g., Trainwreck Express). These diodes (also called “snubber” or “flyback” diodes) prevent undershoot on the power tube plates due to inductive kick and reduce upper harmonics thereby reducing “fizz”.

The Ideal amp controls have been updated.

Added Brit Studio 20 Amp model based on a Marshall SV20H.

Added Plexi 50W 6CA7 Jumped Amp model. This is simply the jumped version of the Plexi 50W 6CA7.

Renamed USA Clean to USA Rhythm 1 to be more in line with actual amp.

Reduced CPU usage in some cases.

Fixed wrong coupling capacitor value in 1959SLP Treble, 1959SLP Jumped and 1987x Treble amp models.

Fixed wrong resistor value in tone stack of Solo 88 Rhythm and Lead models. Probably not audible though.

Fixed low frequency behavior of Recto2 models due to loss of precision.

Fixed wrong treble pot taper in CA3+ models.

Fixed wrong capacitor value in Friedman HBE V1 Fat model.

Fixed wrong resistor value in AC-20 12AX7 models.

Fixed wrong Depth knob taper in Archean models.

Fixed High Mid control in Drive block set to minimum when importing presets created prior to 19.01.

Various other fixes and improvements.
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ham and cheese -> you're on a roll. haven't even had a chance to try the plexi jumped yet and here u r w another update... thank you for what you do!
Mark IV is great! Not sure, but there is sth. with the gain and volume level of the Mark IIC model (Deep Bright).
Anyone else feeling that a lot of the amps are 'woofy' with this beta...? Noticed it on the Marshalls and Atomica; have to apply an amp low cut at 100Hz for the input EQ.
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