[sdiy] DCO amplitude with filtered PWM

[Ove Ridé]

I'm going to assume without evidence that it's a Siemens Taurus locomotive.
(Search for videos of Siemens Taurus singing locomotive.)

On Tue, 28 Aug 2018, 12:50 Adam Inglis, <21pointy at tpg.com.au> wrote:

> We’re gonna need more details about the train…
>
>
> > On 28 Aug 2018, at 7:30 PM, Declare Update <declareupdate at gmail.com>
> wrote:
> >
> > Howdy list,
> >
> > I’m on a long train in Japan, just thinkin’ about synths, as usual.
> >
> > Does anyone have any experience using filtered PWM to control the
> amplitude of a “normal DCO”, ie with a transistor shorting the cap on an
> integrator? Looking at the Juno 6 schematics, I see they used a 7-bit DAC
> to feed the integrator. Some napkin/train math tells me I could use 8-bit
> PWM at about 90khz (easy on stm32), filter it at 9khz, and control the
> amplitude just fine. I’ve been using real DAC outputs of fancier chips to
> do this recently, which works great, but if PWM is fine then I could do 2-4
> voices on $0.50 chip ¯\_(ツ)_/¯
> >
> > anything totally wrong or silly about this? any experience here?
> >
> > Chris
> > Sent from my iPhone
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