Mark I/II:
www.fractalaudio.com/downloads/firmware-presets/axe-fx-2/Quantum/4.0/axefx2_Quantum_4p00beta.zip
XL:
www.fractalaudio.com/downloads/firmware-presets/axe-fx-2/Quantum/4.0/axefx2_xl_Quantum_4p00beta.zip
XL+:
www.fractalaudio.com/downloads/firmware-presets/axe-fx-2/Quantum/4.0/axefx2_xlplus_Quantum_4p00beta.zip
Axe-Fx II Quantum Firmware Release Notes
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4.00
Improved power tube plate current vs. grid voltage accuracy. New models more accurately reflect how the response is higher order at lower grid voltages and “relaxes” into a lower order response at higher grid voltages. This improves feel when the virtual power amp is overdriven and improves harmonic content accuracy.
Note that existing presets will NOT be affected. Any existing preset will have its local Modeling Version (under the Adv tab of the Amp block) adjusted to its previous value. To use the new modeling you will need to set the Modeling Version parameter to “Latest”. Any new presets that are created will use the Modeling Version selected in the Global menu. For example, if an existing preset was using Q3.xx modeling it will still use Q3.xx. To use Q4.00 you would need to set the Amp block Modeling Version to “Latest”. If you create a new preset and the Global menu Modeling Version is “Latest” the new preset will use Q4.00 modeling.
what I'm noticing is a more extended low end, almost like modeling vQ3.xx has a filter on it and switching to latest turns it off. If anything that extra frequency response might be pushing more air through your speakers if I had to infer. either way that extra range really adds some depth even without touching the patches besides the modeling versionI don't know if it's placebo or good air, but I seem to be able to get good musical feedback at lower volumes than previously when using the beta. Looking forward to playing it with the band this Thursday.