[sdiy] Linear Analog Synth Portamento

[Scott Gravenhorst]

David G Dixon <dixon at mail.ubc.ca> wrote:
>> Don't know why I didn't mention this before:
>> 
>> PAiA Fatman is a linear analog synth that has portamento 
>> implemented using a capacitor and a pot as a simple RC 
>> passive lowpass filter.
>
>Yes, but a pot-and-cap does give "linear portamento".  

I'm not sure I fully understand the implications of "linear portamento".  

What I hear from my Fatman sounds natural enough to me.

So what am I missing?  Is "linear portamento" bad?  What won't "linear portamento" do
that I need or want?

>For that, you need
>something like Harry Bissell's brilliant MorphLag circuit.  In short, (at
>the minimum) it requires a Miller integrator and a comparator to compare the
>input voltage and the inverted integrator voltage and provide current drive
>to the integrator depending on the sign of the difference.  When the input
>and output voltages are equal, the comparator is forced to an output of zero
>volts with a tiny bit of negative feedback.
>

-- ScottG
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-- Scott Gravenhorst
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