[LAU] master levels

Chris Caudle chris at chriscaudle.org
Mon Feb 2 18:24:41 UTC 2015

> From: Brent Busby <brent at keycorner.org>

> Ardour is doing 32-bit FP math to handle samples internally.
> And yet, when I change the volume on the master fader, even if I
> compensate for the volume change on my RME Multiface's physical volume
> knob for the headphone monitor, I'd almost swear I can hear some sort of
> change in the audio.

To compare two versions of the same audio, the two versions must be level
matched to within 0.1dB.  Differences of just a few tenths of a dB can
sometimes be heard as a slight timbre difference, usually the slightly
higher level version sounds just a tiny bit brighter.  That requires
matching level to almost 1%, or if using consumer style levels of 2V RMS
max output, matching to within 20mV at max output.
It is difficult to verify at the analog outputs, but should be relatively
straightforward to compare separate files. Finding the right software to
display to that level of precision might be tricky, I'm not sure.

> I'm probably just fooling myself

That is a possibility, but it is a lot more likely that you are not
actually compensating exactly for the level change with your headphone
level control.
Even if you manage to adjust your headphone level control to within 0.1dB,
a lot of analog level controls can't necessarily hold to within 0.1dB over
time due to changes in the resistance with temperature, or mechanical
friction and spring effects that drag the contact back slightly after you
let go.

> In a related question (which was the real reason I wanted to know), what
> kind of levels should we be shooting for in the master output anyway?

Everyone should read Bob Katz's original two part article on level and
metering recommendations:



tl;dr version: Use calibrated monitor levels and set the levels to sound
appropriate for the style of music you are mixing, like used for mixing

Chris Caudle

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