[sdiy] a different kind of slide

[mark verbos]

OK i guess i was wrong about that part. The 303 wasn't really the point, 
it was just a side note. I don't know where I got that from.

The point is the ability to switch in and out the slide remotly, control 
the length of a linear slide form voltage and sync the slide *length* to 
the length of a sequencer step, in order to make sequences that switch 
between stepped and slid notes and make multistage envelopes. The side 
product of this is that you can make linear ramps from one note to the 
next that are always the same length and can jump from any two notes in 
that time.

As far as I understand, an exponential slope is a curve. A linear slope 
is a straight line. Just like in envelopes. In fact the core of a 
voltage controlled envelope is a voltage controlled integrator.

mark

Colin f wrote:

>----- Original Message -----
>From: "mark verbos" <a0284520 at addcom.de>
>To: "synth DIY" <synth-diy at dropmix.xs4all.nl>
>Sent: Monday, March 18, 2002 9:55 AM
>Subject: [sdiy] a different kind of slide
>
>
>>Normally, when the subject of slide or portamento comes up the 2
>>variations on the theme that are discussed are linear and exponential
>>slide. You of course have control over the speed of the slope.  Since my
>>modular is of the Buchla aesthetic, I favor the linear slope variety.
>>All controllers should be linear and all VCO, VCF and VCF inputs
>>exponential in response to them.
>>
>
>The linear/exponential slopes also differentiate constant rate/constant time
>portamento.
>
>>A Roland TB-303 uses a microprocessor based sequencer that
>>outputs a slide between notes that is the same length no matter how far
>>it slides. For 10 years I have been interested in this type of slide,
>>but have never been able to imagine a module that would obtain it.
>>
>
>The 303 doesn't do anything fancy - it just uses exponential i.e. constant
>time portamento.
>The further from the destination the start note is, the faster the initial
>rate of glide.
>As the cv approaches it's destination it slows down.
>The effect is that no matter how far apart your start and end points are,
>the glide takes the same time.
>(In theory, it never actually reaches, but in practical terms, a certain
>percentage of the distance is close enough).
>To create this type of glide you need a resistor and a capcitor.
>Linear portamento is more complicated - you need a constant current source
>to charge/discharge the cap.
>The reason the 303 had constant time glide is probably because it was
>cheaper.
>
>Colin f
>
>
>