Forums > Max For Live

Amplitude to dB formula

February 12, 2013 | 5:18 pm

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?


February 13, 2013 | 5:26 am

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.


February 13, 2013 | 7:37 am

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.


February 13, 2013 | 7:55 am

This comes pretty close:

– Pasted Max Patch, click to expand. –

February 14, 2013 | 1:29 pm

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

– Pasted Max Patch, click to expand. –

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