[sdiy] Alternatives to Faders

[Edward King]

----- Original Message ----- 
From: "Richard Wentk" <richard at skydancer.com>
To: "Edward King" <edwardcking2001 at yahoo.co.uk>
Cc: "Tom Wiltshire" <tom at electricdruid.net>; "Synth-DIY (list)" 
<synth-diy at dropmix.xs4all.nl>
Sent: Thursday, March 08, 2007 12:08 AM
Subject: Re: [sdiy] Alternatives to Faders


>
[snip]

>
>> I suppose that depends on the individual needs of the operator  and / or 
>> where and how the generated values are going to be used.  Given that 
>> there is likely to be several stages of processing  between the rotary 
>> fader and the audio generation system, it doesnt  hurt to start out with 
>> as much accuracy as possible. Moreover, as  this a rate thing (rather 
>> than an analogue position thing), the  difference between data width is 
>> processor time, not hardware cost.
>> I dont agree with above statement because rate - over position - 
>> essentially means that the limitations are down to calculations  between 
>> the slowest you can possibly move the rotary fader versus  the fastest 
>> you can move it. If you want really fine accuracy, move  the thing very 
>> slowly. If you want to jump to max or get somewhere  quickly, flick the 
>> thing or rotate it quickly and get ready to hit  the "hold" button when 
>> you see the level meter getting close to  where you want to be, moving it 
>> slower as you get near there.
>
> I'm not sure how intuitive this would be.

Ive experimented with it and Im very impressed so far. I would go as far as 
to say I prefer it to faders (personal choice I guess).
I cant speak for anyone else, but I find it very intuitive (hence the 
decision to share my findings).

>The obvious advantage of  faders is that there's a simple linear 
>relationship between 'output'  and position. If you attempt to add a fly by 
>wire (as it were) system  that tries to interpret dr/dt, but needs a 'hold' 
>button to bring it  screaming to a halt, you have a much more complex 
>system that will  probably need a lot of fine tuning before it feels right.

Chances are if you're welting the thing as fast as you can, you're looking 
for the maximum value anyway and since this is a continuous wheel, you just 
let it roll on.
The purpose of the hold button is actually to ensure that you dont knock the 
"faders" by accident.
I'll leave the operation specifics up to those who decide to try it....

As regards the relationship between rate and eventual value, that can be 
defined in software and perhaps even offered as a user configuration choice.
Furthermore, if a given "fader" is designed for a specific purpose and no 
other, then the sizes of the encoder wheels and control wheel can be 
modified to better suit that purpose. Essentially, the smaller in size the 
control wheel is and the larger the encoder wheel is, the more fine the 
control.

>
> The problem isn't actually physical accuracy, so much as operator 
> precision. And the fact that different parameters require different 
> responses. (Faders should be log/dB, filter cutoff should be log fc,  ADSR 
> settings can be all-sorts, depending.)

As its configurable in software, you can set the rate there. So if the 
operator wants finer control, the rate is adjusted. So yes, accuracy is a 
priority. If you begin with significant accuracy, you can dumb it down, 
whereas if you begin with little accuracy, you cant create it from nowhere 
without the information to begin with.

>
> Look at a professional console and you'll see that most of the action  is 
> in -15dB to 0dB range, with a smaller over area of 0dB to +10dB. 
>  Below -15db you don't need nearly as much resolution.

Agreed, but on a synth, the requirements are different. In particular when 
you may want to map completely different relationships.
More or less resolution is down to individual designers, but the principle 
works and - again - its easier to discard or dumb down what dont want that 
it is to create it from thin air.
If you have a rotary fader capable of 16 bit resolution, converting this in 
LUT's or a specific function to 8 bit or other widths is a software function 
(and not a very arduous one).
Most PICs can do this without flexing any muscle.



>
> A 10-bit resolution is more than ample to cover these details,  because 
> even if you assume a 100dB range, you're working with 0.1dB  steps, which 
> is really all you need.
>
> But for maximum *tactile* resolution the range won't be linear, and  you 
> can easily stretch out the most important top 20dB and squash the  rest 
> without losing tactile feel.

Again, this can be mapped in software.

>

[snip] 


		
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