[sdiy] Digital pots for polyphonic portamento..

[Antti Huovilainen]

On Thu, 5 Mar 2009, Jean-Pierre Desrochers wrote:

> i need these 2688 steps in a 5 sec portamento to hear
> a glide without staircase effect..
> But doing so,  the worst case in my example is min portamento which is
> 2 msec overall glide time --> 2msec. / 2688 steps = 744nanosec. per DAC steps!!!!
>
> Do you have a solution on that?

Yes. You keep a constant update rate and stick an RC smoothing filter 
after the dac. The RC filter time constant should be about the same as 
your update rate. So for 1 kHz update rate the TC would be 1ms.

If you don't have enough cpu to calculate RC glide at 1 kHz rate, you can 
lower that rate to say 1/10th and use linear interpolation in-between.

Antti

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