[sdiy] Filter cut off DAC

[cheater00 cheater00]

Bear in mind a reconstruction filter unfit for the DAC can create problems
of its own. I'm not sure any more what those are, though.

On Tue, 22 May 2018 21:40 Tom Wiltshire, <tom at electricdruid.net> wrote:

> Go half-way like Roman suggests with 12-bit and a bit of simple RC
> filtering. The steps from the DAC are small enough that they’re not
> perceptible anyway, and the filter smoothing can be set at something below
> your update rate so that you get a totally analog output. If you’re
> updating the DAC at 5KHz, it doesn’t have to be as low as 200Hz. Switching
> the filters in and out is a clever trick, but it’s a measure of how
> desperate they were back in the 80’s. It was common enough then (on top-end
> gear like the PPG Wave and the Oberheim Xpander, no less!), but it’s not
> what I’d do now.
>
> Tom
>
> ==================
>        Electric Druid
> Synth & Stompbox DIY
> ==================
>
> > On 22 May 2018, at 13:55, paula at synth.net wrote:
> >
> > Roman,
> >
> > Indeed the PPG Wave uses 8bit DACs and has filters it can switch in an
> out.
> > I was hoping to avoid the use of a filter (more parts = more cost), but
> it'll work out cheaper than a decent 16bit DAC.
> >
> > Paula
> >
> >
> >
> > On 2018-05-22 13:40, Roman Sowa wrote:
> >> Do it 12 bit. All you need is resolution enough not to notice
> >> quantization during parameter settings. Regardless if it's just cutoff
> >> on that DAC, or combined with LFO and envelope, it's still the same
> >> amount of filter frequency quantization, so if one cannot notice it on
> >> turning cutoff knob, it will not be noticeable with other modulation
> >> sources added either.
> >> And if you need smooth - just add simple analog filter after the DAC.
> >> Like 200Hz or so.
> >> Roman
> >> W dniu 2018-05-21 o 17:52, paula at synth.net pisze:
> >>>> So what do you want to do that might push the design goal above 13
> bit?
> >>> Just thinking, if you add an EG to an LFO and a few other modulation
> routings I wonder if 12 bits is enough to keep things sounding "smooth".
> >>> Paula
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