Amp block

User contributions

Preamp and power amp

The pre-amp and power amp sections of the amp sim cannot be separated. The power amp can be disabled though, either globally (Global menu) or per preset (turn Sag to zero). Turning off power amp simulation doesn't work well with amp sims that fully rely on power amp distortion such as the Wrecker sim (Trainwreck).

CPU utilization

• Each preset can have two Amp blocks. One Amp block uses about 40%. There's no impact on the DSP capacity because one of the two DSPs is devoted entirely to amp modeling. And each Amp block can also use the X/Y feature to switch between sets of parameters.

Modelling

• The amp modeling in the Axe-Fx II is called G2 and Virtual Vaccuum Modeling modeling, see Fractal Audio website. Part of it is ported to Standard/Ultra firmware 11.

Cliff:

• "Almost all the amps in the AFXII are based on actual amps. The amps I haven't ported yet are because I don't have the real amp yet. I could use theoretical values but I would rather not." Source
• "As you listen to clips from modelers what you start to recognize is a certain "stationary" aspect to the tone compared to the every-changing tonality of a tube amp. Another thing is finger response. With a good tube amp you can vary the tone quite a bit just by how you fret the note and attack it. Modelers tend to make every note sound the same. So I tested some hypotheses and came to the conclusion that it's because a real vacuum tube has a transfer function that is not static. The transfer function is dependent on time, frequency and amplitude. Where you really hear it is in the in-between regions where the tube is just starting to distort. At first I tried some dynamic transfer functions but that was a lesson in futility. So then I created the VVT stuff. In VVT there is an actual vacuum-tube replica in software. You enter the values of the resistors and capacitors on the grid, cathode, etc. and it behaves just like a tube complete with Miller effect, cathode memory, etc. The problem is that it requires an obscene amount of horsepower so the only solution was a dedicated DSP. The other big part of the G2 sound is the output transformer modeling. The OT distorts and as it distorts its inductance decreases which changes the bandwidth and loop characteristics." Source

Global amps

The Global Amps feature has become part of Global Blocks.

Using multiple amp blocks in a single preset

• You can use two Amp blocks simultaneously by using two rows on the grid.
• You can switch between Amp1 and Amp2 using CCs. Or morph between them using an expression pedal: add a Mixer block, input both signal chains into it, use the modifier menu to go from 0-100% on one amp and 100-0% on the other, adjust the curve responses for a smooth crossfade.
• You can use one Amp block and use X/Y switching.