[LAD] Fader mapping - was - Ardour MIDI tracer

Len Ovens len at ovenwerks.net
Wed Aug 20 14:37:43 UTC 2014

On Mon, 18 Aug 2014, Fons Adriaensen wrote:

> A slightly better mapping would be 80 step of 0.5 dB for the
> range +10...-30, then smoothly increase the step size to arrive
> at a minimum gain of -70 dB or so. Even for this the calculations
> are trivial.

I thought this was quite exciting, the idea of being able to use a linear 
input and map it directly to DB. However, Mixers don't look like that, the 
area from plus 10 to -10 takes up a whole lot more room on the fader 
travel than anything lower than that. Here is a picture that shows that:
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.

I think they use a lookup table rather than use any formula. I thought 
this next (analog fader) picture was odd:
-20 to -30 uses a lot more travel than -10 to -20... -30 to off is much 
compressed. I guess that is just the taper on the fader. It appears that 
faders do not have linear or log taper, but rather some custom taper that 
expands the -10 to +10 area for better usability. My Mackie CR 1604 
(yes one of the first ones) with 60mm faders dodges the whole thing and 
puts unity in the middle with +20 on top and off on the bottom. The faders 
are probably a log faders.

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:

> 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. While many people "draw" the fade on the DAW waveform 
(or let the DAW do that for them), what about those who like to do that 
manually? Would that mapping make it harder to fade? Or to put it another 
way, The manual fade would end up being different than with an analog 
recording desk.

If the artist is "drawing" the fade, why use faders at all? Rotary 
encoders would work fine and could be set to arbitray resolution on the 
fly with modifier buttons/keys (The control surfaces I looked at do this). 
In fact, rotary encoders could be better for mixing with a more positive 
feel for one "tick" if they are detented. (maybe use bigger knobs like in 
days of old) Does anyone have any ideas on what wrist movement is more 
natural, less strain? Would it be better to use an up and a down key? 
(maybe with up 10 and down 10 keys as well)

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)

Len Ovens

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