[sdiy] super simple portamento / slide / glide / slew limitingcircuit?

[Tom Wiltshire]

If you ignore a few bits dealing with the Gate, the SH101 does it pretty much like the Steiner circuit, and it sounds like the SH101 is a reasonable model. It doesn't bother with the first buffer, but the resistor, cap to ground, and second buffer are all present.

If you want it super-simple, Todd, just give it a go. See if a resistor and a cap to ground is enough. If it doesn't work, the whole thing will go hideously out of tune. It'll probably depend on what comes after - if it's a high impedance, you might get away with it.

The point of all the "extra" stuff that people have proposed is mostly just buffers to avoid loading the RC filter, or avoid the RC filter loading something else.

To be honest, I think you might be lucky to get it to work reliably without at least one op-amp, but it's so simple to try it and see that I'd recommend that before you mess about finding a power supply inside the synth. You could probably wire a pot and a cap to the back of the jack somewhere - it has to be worth a shot!

T.

On 13 Jul 2011, at 23:25, David wrote:

> The Steiner follower was made for CVs. 
> 
> David
> 
> -- -----Original Message-----
> -- From: synth-diy-bounces at dropmix.xs4all.nl [mailto:synth-diy-
> -- bounces at dropmix.xs4all.nl] On Behalf Of Todd Sines
> -- Sent: Wednesday, July 13, 2011 2:32 PM
> -- To: David G Dixon
> -- Cc: synth-diy at dropmix.xs4all.nl
> -- Subject: Re: [sdiy] super simple portamento / slide / glide / slew
> limitingcircuit?
> -- 
> -- hi everyone,
> -- 
> -- Thanks all for the help.
> -- 
> -- But... maybe I wasn't clear..
> -- 
> -- This is intended to modify the Roland DG series CMU-810. It's essentially
> an analog synth
> -- tabletop expander that sounds a lot like an SH-101, MC-202 or SH-09.
> -- http://matrixsynth.blogspot.com/2009/10/roland-cmu-810-compusynth-modded-
> -- analog.html
> -- [in the end I'd love mine to end up like this one, but for now, I just
> wish to add
> -- portamento]
> -- 
> -- What's different about this compared to the rest is that there's no
> portamento of the
> -- incoming CV / gate jacks.
> -- So I'd like to cut the track for incoming CV, insert this _SUPER_ simple
> portamento
> -- circuit before it starts triggering the osc.
> -- As I'm sure you know, Roland follows a linear pitch scale so I don't need
> a switchable or
> -- dual mode circuit.
> -- 
> -- Something about the first circuit from EM seems closer to what I need
> [versus circuits that
> -- need their own power, etc].
> -- 
> -- Is this helping or did I miss something from before? because it seems
> like all of these
> -- circuits are for much more complex applications, no?
> -- 
> -- Thanks... in advance!
> -- 
> -- 
> -- +odd
> -- --