[sdiy] Re-inventing the knob (was Control Interfaces)

[vintvolt]

Hi everybody,
I've been following the recent thread about control interfaces with 
interest. That brought back to my mind an idea I had some time ago 
about knobs. If you search the analogue heaven archive for "Old radios 
and knob inertia" you will get the basic idea and some discussion. Here 
a summary:
The concept is "stolen" from a big bulky dial knob in an old radio I 
own. If you turn that knob hard to one side, it will keep spinning for 
a while after releasing it.
Of course such kind of mechanical inertia on a knob is not easy to 
build and integrates difficultly in a synth...
Imagine an endless rotary encoder with *software* inertia behaviour. It 
could have an adjustable "friction" parameter. If friction is very high 
it would act just like a standard encoder, but if the friction is 
reduced, the destination parameter, e.g. cutoff, will keep on 
increasing/decreasing after releasing the knob. In the meanwhile you 
could use that hand to modify other parameters.
Additionaly consider very low friction... when the parameter reaches 
the upper or lower limit, it could "bounce back" in the other direction 
for some nice LFO modulations.

Now I have a chameleon, I am seriously considering the implementation, 
although I'm currently concentrating on the DSP side (programming a 
frequency shifter...)