Amplitude to dB formula

Dave Mollen's icon

I want to control send/return dials with [live.remote] through amplitude values. For that I need to know what formula Ableton Live uses to go from 0-1 to dB values. Unfortunately it doesn't use the same formula as [atodb]. Does anyone know?

Roman Thilenius's icon

it probably uses the same formula, log 10 / 20, this is what all audio apps use.

but most audio apps also use custom scaling of the user interface sliders - typically
the lower end is scaled in a curved way to give more control over the lowest 30 dB/A.

this is probably what you are seeing.

Dave Mollen's icon

Yes. The first half is curved, up to -20db. And from -20dB to 0dB it's linear.
But I'm struggling with the curved part.

Dave Mollen's icon
Max Patch
Copy patch and select New From Clipboard in Max.

This comes pretty close:

Dave Mollen's icon
Max Patch
Copy patch and select New From Clipboard in Max.

I have come to a solution. Here's the lookup table to control sends with exact amplitude values.