Optical compression: the slow one
What a photocell does to timing, why an opto can hold a whole mix steady without anyone hearing it, and when to reach for one instead of a faster compressor.
The slow one. A photocell rather than a circuit decides the timing, which means it grabs gently and lets go in two stages — and that's why an opto can hold a whole mix steady without anyone hearing it work. Reach for it when the level wanders rather than when the transients are too big.
The controls
Every range and starting value below is the one the processor actually uses — this page is generated from it.
- Peak reduction
- The only real control. Turn it up until the meter shows 2–3 dB on the loud sections and leave it there.
- Gain
- Makeup level, to put back what the cell took off. Set it so bypassing the box doesn't change how loud it is.
- Emphasis
- Tilts what the detector listens to upwards, so cymbals and sibilance pull it down instead of the kick doing all the work. Turn it up if the mix breathes on every bass note.
- Blend
- Parallel blend. Pulling this back to about 70% keeps the transients that the compression is flattening — the trick behind most 'glued but still punchy' masters.
- Mode
- Compress is the gentle 3:1 you want across a mix. Limit tightens it right up for anything that still jumps.
Sonic Station's mix finisher runs this entirely in your browser — the audio is never uploaded anywhere.
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