Choose what you’re compressing, then select your goal. The compression calculator gives you two paths depending on your setup:

If you have a specific compressor type – opto, FET, VCA, Vari-Mu – the topology recommendations tell you which suits the goal. These compressors have their own built-in character and often their own timing behaviour. An LA-2A doesn’t have attack and release knobs because the circuit handles that automatically. An 1176 has fixed timing options rather than free-range millisecond values. When using these, you’re leaning on the compressor’s inherent sound – just set your threshold and ratio and let the character do the work.

If you’re using a stock plugin or generic compressor with full control over attack, release, ratio, and threshold – that’s what the settings are for. These numbers approximate the behaviour of the recommended topology on a compressor that doesn’t have that built-in character.

So it’s not “use these settings on an LA-2A.” It’s “use an LA-2A if you have one, or dial in these settings on a stock compressor to get in a similar ballpark.”

The recommendations come from real-world mixing practice. They’re starting points that get you moving quickly so you can spend more time listening and less time guessing.