Levels
Input trim, output level and preset level do three different jobs on the Axe-Fx III. Using one for another's job is where rigs get confusing.
Fractal give you more level controls than any other modeller, and put meters on all of them. That is a good thing once you know which control does what, and bewildering before. There are really only three jobs: get the guitar into the converter cleanly, get the output to match what you plugged into, and make your presets the same loudness as each other. They are separate jobs, and doing one with the other's control is where rigs go wrong.
Axe-Fx III Owner's ManualInput trim is not a gain control
The single most misunderstood control on the platform. Input trim is not a gain control and does not change your tone. As you lower the trim into the converter, the output of the converter is raised by the same amount — so what reaches the amp models, and what you hear, stays exactly the same. It is there to optimise signal-to-noise, not to push the front end. If you want more gain, that is the Amp block's Drive.
- Step 1
Set the input trim once and forget it
Plug into the Instrument input, pick your loudest pickup, open everything up, and play hard while you watch the INPUT 1 meter. The red LED lights at −6 dB, which is still safely below clipping — so the target is for your loudest playing to tickle the red, not to avoid it. Adjust it under SETUP : I/O : Input with the A knob. A quieter guitar that never reaches red is fine. Inputs 2, 3 and 4 each have their own trim on the same page.
- Step 2
Then match the outputs to what you plugged into
Outputs 1 and 2 arrive set for consumer line inputs at −10 dBV. If you are feeding professional gear running at +4 dBu, change it: SETUP : I/O : Audio, then Output 1: Output Level or Output 2: Output Level to +4 dBu. The four front-panel LEVEL knobs then ride each output pair independently.
- Step 3
Outputs 3 and 4 are the four-cable-method pair
They are designed for unity-gain use — the four-cable method, or anything else that goes back into a traditional amp. Unity happens with the OUT 3 and OUT 4 Level knobs turned fully clockwise, which is the opposite of the instinct to leave a knob at noon.
If the outputs clip, the trim is not the problem — your presets are too hot. Fix it with preset levels, starting at the Amp block.
Making your presets the same loudness
This is the third job, and the one that decides whether a set is playable. It has nothing to do with the two controls above — those are set once and left alone.
Use the Amp block's Level, not anything else
The rule of thumb across the whole platform: when a preset, scene or channel is louder or quieter than its neighbours, fix it with the Level parameter of the Amp block. Everything else — output knobs, block levels, the mixer — has a different job, and using them for this is what makes a rig impossible to reason about later.
Watch the meters, but do not obey them
Zoom the Layout grid out and VU meters appear across the top, scaled −20 to +10 with a red line at 0. That is an internal level, not a dBu reading. Play the same thing while you switch presets and aim to have the meter hover around the line. Chugs will always hit hardest. Trust the meters, then use your ears anyway.
Make the loud ones quieter, not the quiet ones louder
When you deliberately want a lead to sit above a rhythm, the manual's advice is to bring everything else down rather than push the lead up. Boosting is what causes clipping, and these units have enough headroom and a good enough noise floor that a preset sitting well below the others costs you nothing.
Some blocks break the rule
If a compressor or a gate follows the amp, changing the amp's Level changes how they behave, so adjust the last dynamics block instead. Same for a nonlinear effect after the amp — tape saturation, a bitcrusher — and if you are leaning on the drive inside the Cab block's preamp, level that block rather than the amp.
Levels are half of it. The other half is the cab block — on into anything full-range, off into anything that ends in a real guitar speaker.