Gain staging, properly
The most-asked and worst-answered question about this unit. Five stages in order, and why the two pieces of advice that appear to contradict each other do not.
“0 dB” and “just below clipping” are not rival answers. One is the default, the other is the check. Do them in that order and the argument disappears.
Why this is confusing, and whose fault it is
Search this question and you find two camps. One says leave input gain at 0.0 and stop fiddling. The other says set it just below clipping. Both get repeated with confidence, neither gets reconciled, and Neural DSP's own forum carries threads titled some version of “thoroughly confused about gain staging and about to give up”.
The two positions are not in conflict. 0 dB is the design target — the unit is built to handle a hard-strummed humbucker there. “Just below clipping” is the verification that this holds for your particular guitar, and the adjustment you make when it does not.
One is a starting point. The other is a test. Presented as rival opinions they are unresolvable; presented in sequence they take two minutes.
The five stages, in order
Work these top to bottom. Each assumes the ones above it are already set.
- 01Input — I/O Settings, IN 1 LEVEL, start at 0 dB.
- 02Verify — same screen, play harder than usual, meter should just tickle the red. Adjust only if it does not.
- 03Preset output — the lane output at the end of the Grid row. This is where preset-to-preset level matching actually happens.
- 04Device output — the output level in I/O Settings. Set it to 0 dB and leave it; it is a device-wide trim, not a per-preset one.
- 05The knob — VOLUME to maximum while you set all of the above, then trim it for the room.
Setting levels with the volume knob halfway means every meter on the unit is lying to you about what front of house receives. Max it, get the levels right, then trim.
Quad Cortex Wiki: Gain StagingHeadroom: 12 dB clean, 6 dB distorted
Clean tones have a far higher peak-to-average ratio than distorted ones. Distortion is compression — a saturated patch simply does not spike the way a clean one does.
This is why matching presets by ear at the same apparent loudness is how clean patches end up clipping in the room while the high-gain ones are fine. Leave twelve decibels of headroom on cleans and six on distorted, and stop trusting your ears for this one specific job.
Three traps that are not your fault
Each of these is a real property of the unit rather than a mistake, and each one has cost somebody an evening.
- You cannot see the meter and the control at the same time — the output meter and the lane output control are on different pages. Turn the lane output up until it flashes red, then back it off a known number of decibels. You are finding the ceiling rather than watching a needle.
- A TS cable on OUT 3/L or OUT 4/R halves the output voltage. Those jacks are balanced; you need 6 dB back to reach unity, and you have spent 6 dB of headroom getting it.
- The FX loop sends run at line level by default. Pedals expect something much quieter — pull the send down, starting around −5 dB.
Do not reach for a limiter to tame a chain that is too hot. Digital clipping does not soften the way analogue clipping does, and limiting trades a level problem for a tone problem. Find the stage that is too hot and fix it there.
Quad Cortex Wiki: Gain Staging