[sdiy] Alternatives to Faders

[Richard Wentk]

On 7 Mar 2007, at 17:40, Tom Wiltshire wrote:

> Edward,
>
> On 7 Mar 2007, at 15:08, Edward King wrote:
>
>> you know the pitch-bend and modulation wheels you normally get on  
>> synths?
>> Thats the way Im going at the moment...although the wheel Im using  
>> is okay, Im having problems finding wheels / dials that are  
>> similar to modulation wheels so if anyone knows of any, I would be  
>> very grateful. They need to be roughly 10mm wide and the same  
>> diameter (or close to it) as modulation or pitch-bend wheels.
>
> I don't know of any, but I recently looked into buying 10mm acrylic  
> sheet with a view to cutting circles out of it for exactly this  
> purpose. I was only going to need two, so thought to do it by hand,  
> but if you needed lots, you could probably get someone to machine  
> them for you.

I think an interesting design would be mod-wheel acrylic with colour- 
coded LED backlighting, varying with the applied level, or even used  
as a rough guide to active channel dynamics - e.g. the colour could  
indicate peak or RMS level.

Four LEDS per wheel -= blue, green, orange/yellow and red - would add  
hugely to cost and complexity. But it would look extremely cool in  
action. :-)

> I have also struggled with the problem of how to represent high  
> resolution digital values (even 10 or 12 bit is hard) using LEDs or  
> such like. One thing that is worth remembering is that analogue  
> controls don't really display the position with the theoretical  
> infinite resolution they're capable of. Consider: My Korg Polysix  
> has scales marked 0-10, with 5mm between tickmarks. Assuming the  
> human eye can differentiate positions down to 0.5mm, I could  
> recognise only 100 different positions on the scale. Even assuming  
> that I could recognise positions only 0.05mm apart (highly  
> unlikely) only gives me around 10 bit resolution.

Really, you can't. And given that even long-throw faders max out at  
maybe 9-bits of precision - 10-bits if you really push the design -  
the reality is that any fader or knob control surface has strictly  
limited physical resolution.

Hex appears on MIDI and keyboard controllers often enough not to be a  
problem in the keyboard market. It's more of an issue in the mixer  
market, where audio engineers may be less used to it. But there's no  
good reason not to map 2 digit hex to a 0-99 decimal display if  
that's going to be a problem.

Things like zipper noise and fade smoothing are usually more of a  
problem. Some digital designs ignore them completely with - as they  
say - hilarious consequences.

Richard