[sdiy] Midi2cv with at least 8 channels .. ?

[Seb Francis]

Not sure about this .. for example looking at the datasheet for the Analog Devices SMP04 it gives a droop rate of up to 25mV/S (typical is 2mV/S, but it rises with temperature amoung other things) which would be quite significant for a VCO.  A refresh rate of 50 Hz or so ought to do it though.  Maybe a S&H with discrete components would achieve much lower droop?

Offset voltage variation looks not too bad .. about 1mV over 100C.  Offset voltage vs input voltage is basically linear between 0.5V and 9V, but the slope does change depending on the load (about 1mV difference at 9V when jumping from a 20K to 10K load).

Overall, it looks good enough (although I'm very far from being expert - most probably Paul can spot some factor which I've missed ;-)

Seb



Rob B wrote:

> As for the refresh, well, with modern components, leakage should be a
> minimum such that you prlly only need to refresh every second or so? I am
> sure you can get around to it by then. :)
>
> Just use an "any change=refresh" so, no matter *what* changes, you refresh
> *all*.
>
> I dunno, I have seen a sample and hold hold a good voltage for upwards of
> 20mins with no significant droop..
>
> Rob
>
> ----- Original Message -----
> From: Tim Ressel <madhun2001 at yahoo.com>
> To: Seb Francis <seb at is-uk.com>; Rob B <cyborgzero at comcast.net>;
> <synth-diy at dropmix.xs4all.nl>
> Sent: Wednesday, September 18, 2002 12:13 PM
> Subject: Re: [sdiy] Midi2cv with at least 8 channels .. ?
>
> > I just used 4051s, lm324s and 0.1uF caps for my 8-chan
> > version. Seems to work fine.
> >
> > --TR
> >
> > --- Seb Francis <seb at is-uk.com> wrote:
> > > Seb Francis wrote:
> > >
> > > > I couldn't fine any S&H arrays from my normal
> > > suppliers - maybe I was searching for the wrong
> > > name.  Can anyone recommend any?
> > >
> > > sorry, forget this question .. I found them now!
> > > was too late at night when I was looking before ;)
> > >
> > >
> > >
> >
> >
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