Phon.Audio
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Line-level

Gain staging

Enough voltage to reach full output, without overloading the next input.

Simple

Can the upstream device put out enough voltage to drive the next one to full volume — without overloading its input? Too little and you can never get loud enough; too much and the input distorts before you reach the top of the dial.

The theory

Gain staging checks voltage headroom between stages: headroom_dB = 20·log₁₀(maxOutput / inputSensitivity). Positive headroom means the source can reach the voltage the next stage needs for full output. The engine also flags the opposite failure — if the source's max output exceeds the downstream overload point, the input clips at high settings. Good structure means comfortable headroom on both ends.

For experts

Gain structure ladderA vertical voltage ladder showing a 4 volt source maximum sitting above a 2 volt input overload point, the 0.7 volt input sensitivity, and the noise floor, with the usable window and the clipping zone marked.usable window — signal fitscleanly between the limitssource exceeds overload —input clips regardless of the pot4.0 VrmsSource max output (balanced DAC)2.0 VrmsDownstream input overload point0.7 VrmsInput sensitivity — full output reachednoiseDownstream noise floor4 V into a 0.7 V amp = ~15 dB excess gain — all your listening happens at the bottom of the pot

The subtle, real-world failure mode here isn't too quiet — it's the gain mismatch that crushes usable volume range. Pair a high-output DAC (4 Vrms balanced) with a high-gain power amp (low input sensitivity, say 0.7 V for full output) and you reach ear-splitting levels in the first 9 o'clock of the volume knob, leaving you riding a tiny, channel-imbalance-prone arc at the bottom of the pot. It's not distortion, it's ergonomics — and it's why "more gain" is often actively worse. The flip side is the overload-clipping case the engine warns about: a 4 V source into a 2 V max input clips the input stage regardless of where the volume sits downstream, because the damage happens before attenuation. Unity-gain and the "gain before attenuation" ordering inside a preamp are the design answers; the engine just checks you haven't stacked the stages into a corner.

headroom=20⁢log10(VmaxVsens) dB

Positive: the source can drive the next stage to full output. Also check V max against the input's overload ceiling.

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