[sdiy] TOGs and Vibrato/Pitch bend (was Vibrato range)

[Tom Wiltshire]

Hi Tim,

I'd be interested to know where you get to with this, since this is something I've bashed my head against too (see "4046 overclocking a PIC" in Aug 2015). Like you have done, I had a 4046 as a master oscillator and simple uPs acting as a single note dividers. Since it is so easy to do so, each uP outputs all the required octaves for that note.

I was using a variation of Thomas Henry's exponential 4046 VCO, but I found it extremely difficult to get reliable results out of the 4046. The between-chip variation was *huge*, although to be fair I was testing chips from several different manufacturers. Still, it'd be nice to believe you could design a circuit that would work with any 4046, so that was why I was trying with three different types. There was about a factor of 4 in frequency between them.

I used the Expo VCO because it seemed like the more musical option for a "Pitch Bend CV" input, but I think it probably throws up some of the problems I was seeing. For a more limited range, say a tone either way for vibrato, a linear CV might be fine.

Anyway, good luck with your endeavours, and do please keep us informed.

Regards,
Tom


On 25 Jun 2016, at 18:33, Tim Ressel <timr at circuitabbey.com> wrote:

> It is easy enough to rig a 4046 as a VCO and use it to do pitch bends and vibrato. The hard part is this: how to keep it in tune? Is it enough to simply use low temco timing components and provide a fine tune knob? I have dreamed up a complicated method of using a PLL and a processor to keep the clock in tune, but is it necessary? I kinda hope not, because it is techically cool but hugely complicated (I tend to over think things).