[LAD] Fader mapping - was - Ardour MIDI tracer

Fons Adriaensen fons at linuxaudio.org
Thu Aug 21 09:14:28 UTC 2014

On Wed, Aug 20, 2014 at 07:37:43AM -0700, Len Ovens wrote:

> http://www.allen-heath.com/media/GLD-Faders_2800.jpg
> As you say 0 is a special case for off.
> everything below -10 is the same amount of travel for 10db.
> -10 to -5 and +5 to +10 are the same travel for 5db that the lower
> parts are for 10db.
> -5 to +5 uses more travel again.

To me it looks as if the range -10..+10 is expanded. -5..+5 looks
even more expanded but that's just because they left out the the
marks at +/-2.5.

This is very easy to achieve with a simple calculation. The
only problem is that the 'dB/mm' value changes almost stepwise
at -10, this makes a smooth fade more difficult. The solution 
it use either more linear (in dB) sections, or to make the
dB/mm change more smoothly below the linear region. This is
my favourite solution. Conversion in both directions is still
quite easy, code on request. 

How much this matters depends on the application. Fades are 
rare in music mixing, but a very common thing in e.g. broad-

> So I was wondering if there would be a difference in faders built
> for FOH and recording, this image of a Classic Neve 8068 Console
> from the 70s (or earlier?) shows the same kind of mapping though:
> http://lghttp.17114.nexcesscdn.net/808784/vking/media/catalog/product/u/s/used_33993_4.jpg

Probably using analog VCA faders, which offer some (limited) freedom
in modifying fader taper.

In practice, if the resulting taper is OK you'll adapt to it fairly
soon. As you do to e.g. a new car.
> >There is no problem with CPU use. On the sender side you transmit
> >0..127 which is just 7 bits of an ADC measuring the voltage from a
> >linear fader or pot, there is no mapping at all.
> Yes, I liked the idea of that: real easy to build. Probably fine for
> static mixing too.

The only function of the encoding is to represent the fader position
in the best possible way. How that is interpreted later and mapped to
dB (or anything else) is a separate matter.

> I guess what I am saying is that todays control surfaces are based
> on operating methods from the 60s and 70s. Have operating methods
> changed in such a way that control surfaces should be different?
> Should operating methods change because of todays tools? Can a
> manual fade be done in a more musical way than a drawn fade?
> (thinking about the ear to brain feedback vs. repeat and tweak)

It all depends on the application. For example, FOH and monitor mixers
have always been different, as have mixers designed for broadcasting.
Compared to the 70s and 80s (popular) music mixing has changed, but
IMHO mostly beacuse the music itself has changed, and also because
a lot of mixing is now done by people who have no training for it
at all and are just working by trial and error. One result of that
is sessions with lots of plugins in each and every track, usually a
clear sign of amateurism.



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