Old 05-07-2021, 10:24 AM   #1
kirk1701
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Default Compressor threshold

I'm fairly competent with compression, but I've not used a lot of VCA comps(SSL, Focusrite, etc.)

I'm noticing particularly on channel strips the threshold has a range above 0db, often +10. What's the purpose of this? I've always thought threshold was 0db and below. Is this expansion territory?
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Old 05-07-2021, 10:41 AM   #2
JayJSE2
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I'm pretty sure it's because those channel strips (and really all analog gear) use dBu rather than dBFS (which DAWs use). So setting the channel strip comp at 0dB is actually the same as setting a plugin like reacomp to something like -10dB (I can't remember the exact conversion).
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Old 05-07-2021, 12:00 PM   #3
kirk1701
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Originally Posted by JayJSE2 View Post
I'm pretty sure it's because those channel strips (and really all analog gear) use dBu rather than dBFS (which DAWs use). So setting the channel strip comp at 0dB is actually the same as setting a plugin like reacomp to something like -10dB (I can't remember the exact conversion).
So gain reduction is still happening.
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Old 05-07-2021, 12:16 PM   #4
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Originally Posted by kirk1701 View Post
So gain reduction is still happening.
Yeah, it's not working as an expander, it's just that the numbers on the knobs are some arbitrary "analogue" value rather than the more relevant dBFS. The meters are also calibrated to that though, so I guess it is consistent.

Expansion is usually with the gate section on olde-timey gear. If you're talking about the Brainworx console plugins that is where you'll find expansion.
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Old 05-10-2021, 08:37 AM   #5
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Pretty sure they’re right that it means “dBu” or dBVU rather than dBFS. The scale doesn’t really matter though. A signal higher than the threshold gets compressed. Just because that threshold happens to be greater than zero doesn’t change anything at except that you need hotter signals to trigger it.

I think these plugins general default to 0dbVU = -18dbFS, but you’d kind of have to ask the manufacturer. Some allow you to set that, I think. It has no meaningful relationship to dbu because dbu is referenced to actual real world voltage, and you’d need to look at your interface specs to figure that part out, but it only really matters if you’re trying to use outboard analog gear.
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