Fairlight FX · Restoration · Resolve 21
De-Hummer in Fairlight
A live-interface guide to Fairlight De-Hummer: 50 Hz, 60 Hz and Variable modes, fundamental frequency, Amount, harmonic Slope, Hum-only monitoring and a practical way to remove electrical hum without hollowing out useful low frequencies.
Hum is tonal, so treat it as a tonal defect
1. Interface anatomy
The current De-Hummer controls and what they mean
The labels and visible ranges below are taken from the supplied Resolve 21 interface. The screenshot values are an example state, not recommended universal settings.
50 Hz / 60 Hz / Variable
Choose a fixed mains family when the interference clearly matches the local power frequency, or Variable when the fundamental is shifted or the source is not exactly at the standard mains value.
Frequency · 50–400 Hz
In Variable mode this sets the fundamental around which the repeated harmonic notches are built. The graph helps show that the processor is not just cutting one single frequency.
Amount · 0 to −30 dB
Sets the depth of hum reduction. Increase only until the electrical tone stops being distracting; excessive attenuation can make low-frequency speech or ambience sound hollow.
Slope · Low ↔ High
Controls how strongly the treatment extends across the harmonic series. Use the response graph and Hum-only monitoring to judge whether too many useful harmonics are being caught.
Listen to Hum Only
Lets you monitor what the processor is removing. If recognizable speech, music fundamentals or useful room tone become prominent here, the setting is probably too broad.
Harmonic notch graph
The repeated dips visualize the fundamental and harmonics being attenuated. This is the key difference from broad Noise Reduction: De-Hummer is deliberately tonal and structured.
2. Practical workflow
Confirm that the problem is hum before you start cutting
Blackmagic describes De-Hummer specifically as the Fairlight repair tool for power-line hum. That means it should not be the first answer to fan noise, preamp hiss, traffic or changing room ambience. Those are broader or less tonal defects.
Loop a section where the hum is easy to hear, verify it with Hum-only, choose 50/60 Hz when appropriate or Variable when needed, then raise Amount while watching the notch pattern. Increase Slope only if the higher harmonics are still audible and actually belong to the interference.
Wrong diagnosis
If the noise has no stable pitch or harmonic family, De-Hummer is probably the wrong processor. Try Noise Reduction or a more specific repair method instead.
Too much removal
Deep notches can thin low voices, bass-rich ambience or music. The goal is to make the hum unobtrusive, not to erase every trace at any cost.
3. Repair chain
Remove the narrow tonal defect before broad cleanup
Hum or sibilance first when they are clearly the source of the problem.
Use Noise Reduction only for the remaining steady background.
Move to EQ, compression and the creative mix after repair is under control.
Check the full sentence and the final mix, not only a soloed syllable.
De-Hummer first when obvious
A clearly identifiable mains tone is a narrow defect. Removing it before broad noise reduction can prevent the wider processor from working harder than necessary.
Clip vs Track
Use Clip FX when only one take or device carries the hum; use a track insert when the same electrical problem is stable across the whole channel.
Check after compression
Compression can make residual hum more obvious. Recheck the full chain after dynamics rather than assuming the repair is finished in solo.
Related Fairlight repair guides
Blackmagic's current Fairlight documentation identifies De-Hummer as the cleanup/repair FX for removing power-line hum and confirms clip or mixer-channel application. Exact control labels and visible ranges are taken from the supplied live Resolve 21 interface. A Blackmagic forum answer also confirms the 50 Hz, 60 Hz and Variable options for the Fairlight AFX De-Hummer.