Really simple portamento/slide circuit

Pastedgraphic-1I’ve wanted to include a simple slide in my silly CSQ-100-style sequencer, and I’ve just got this circuit from a post at electro-music working, using a (probably not ideal) LM358 as a buffer running off a single +12v supply, and using a 1M pot rather than the 100k.


Here’s how it sounds on an MS20, with varying amounts of drunken slide.

The 1M pot is too big, I need to change the range to about 200k or so. From what I’ve read, I’d be better off with a log pot but I’ve only got linear ones to hand. I’m thinking I’ll switch the slide in and out of the circuit from the sequencer using a 4066 switch, that’s the next step.

Update: Here’s the MS20 being triggered by the sequencer, using a 4066 to bring the slide capacitor into circuit on 5v triggers from the sequencer, so the portamento only happens on certain notes. Initially I was trying to power the 4066 off +12v and switch it from +5v – If I’d have read the datasheet I would have realised it needs Vdd to switch, duh. Got there in the end.

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  1. 19th April 2020Cabralia says:

    Hi! Do you happen to have the schematics implementing the switch? Sounds really nice!

  2. 20th April 2020ua726 says:

    I rarely drew anything out back then. I think it was literally just putting the 4066 inbetween the opamp input/pot and the capacitor – so opamp input/pot > 4066 pin 1, capacitor on 4066 pin 2, and then the trigger on pin 13.

    On my 100M clone I used the slide from the MC-202, adapted for an external signal – looks like this:

    Adapted 202 slide schematic

    I can’t remember why I chose to run the 4066 off 10V (its absolute max is 20V, rated for 15V), maybe something to do with the trigger voltage.

    Anyway it sounds like this:

    MC-4 > 100M, sawtooth with portamento switched from MPX

    The circuit could be made single-sided with an LM358 or something, but in that case it would struggle to get to 0V.

  3. 20th April 2020ua726 says:

    Should also say that it’d be worth tying the unused inputs on the 4066 to ground

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