<div dir="auto">One way to reduce the noise coming from the MUX control signals is to use grey code instead of binary count, so that only one adress line changes at a time.</div><div><br><div class="gmail_quote"><div dir="ltr" class="gmail_attr">On Fri, 8 Dec 2023 at 15:29, Mike Bryant <<a href="mailto:mbryant@futurehorizons.com">mbryant@futurehorizons.com</a>> wrote:<br></div><blockquote class="gmail_quote" style="margin:0px 0px 0px 0.8ex;border-left-width:1px;border-left-style:solid;padding-left:1ex;border-left-color:rgb(204,204,204)">
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<li style="font-size:11pt;list-style-type:"\0027a2 ""><span style="font-size:11pt">OTOH I would love to see someone doing 100-outs MUX with single DAC
</span><span style="font-size:11pt">spitting 16-bit precision at 1Msps
</span><span style="font-size:11pt">Roman</span></li></ul>
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I think the uneven capacitance alone to each of the S/Hs would make this impossible. And the noise from all the control signals to the gates are almost bound to cross critical tracks.<br>
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<div id="m_-8114127908063730212divRplyFwdMsg" dir="ltr"><span style="font-family:Calibri,sans-serif;font-size:11pt;color:rgb(0,0,0)"><b style="font-family:Calibri,sans-serif">From:</b> Synth-diy <<a href="mailto:synth-diy-bounces@synth-diy.org" target="_blank" style="font-family:Calibri,sans-serif">synth-diy-bounces@synth-diy.org</a>> on behalf of Roman Sowa <<a href="mailto:modular@go2.pl" target="_blank" style="font-family:Calibri,sans-serif">modular@go2.pl</a>><br>
<b style="font-family:Calibri,sans-serif">Sent:</b> 08 December 2023 14:07<br>
<b style="font-family:Calibri,sans-serif">To:</b> Danjel van Tijn / intellijel <<a href="mailto:danjel@intellijel.com" target="_blank" style="font-family:Calibri,sans-serif">danjel@intellijel.com</a>>; SDIY <<a href="mailto:synth-diy@synth-diy.org" target="_blank" style="font-family:Calibri,sans-serif">synth-diy@synth-diy.org</a>><br>
<b style="font-family:Calibri,sans-serif">Subject:</b> Re: [sdiy] Generating a large number of CV outputs</span>
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<div><span style="font-size:11pt">I'm triggered, because that's something I was recently evaluating (but<br>
don't feel like doing for various reasons).<br>
The DACs can be as cheap as they wish, but will never be S&H-MUX cheap.<br>
Surely there are cheap excellent 12-bit DACs now with price per channel<br>
below $1 but that's still a lot of money. You could also consider<br>
96-channel DAC and just don't bother designing huge circuitry around it,<br>
but not only it cost $80 in singles but also is huge BGA monster.<br>
<br>
I reckon you're not doing it for space or military, so IMHO the mux way<br>
is the only way still.<br>
<br>
With 100 outs at "few" kHz update rate you're struggling with 1us analog<br>
MUX settling time, and when you say 16-bit, that makes me shiver.<br>
What you can do is split it to couple of separate muxes with their own<br>
DACs, and feed them sequentially. Huge analog circuitry with lots of<br>
muxes, opamps, caps and countless meters of traces will be happier<br>
getting an update every 10us rather than 1us. Interlace DAC update<br>
moments with MUX address changes to make sure new output is well settled<br>
before MUX opens.<br>
Also, with multiple DACs and MUXes you can spread the circuitry on the<br>
board so DAC's opamp will not have to drive too much, but only a couple<br>
of MUXes gathered around it.<br>
<br>
OTOH I would love to see someone doing 100-outs MUX with single DAC<br>
spitting 16-bit precision at 1Msps<br>
<br>
Roman<br>
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<br>
W dniu 2023-12-08 o 01:35, Danjel van Tijn / intellijel pisze:<br>
> What is the current ideal way to generate a large number of CV outputs<br>
> from a single CPU?<br>
><br>
> Let's say I wanted to generate 100 outputs with an update rate of a few<br>
> kHz and an equivalent bit depth of 12 or 16 bits.<br>
><br>
> I know that back in the day when DACs were extremely expensive, the<br>
> designs would use a single DAC and then demux to a bunch of S&Hs.<br>
><br>
> Now that DACs are cheaper, is it better to chain a bunch of 8- or<br>
> 16-channel DACs?<br>
><br>
> Or would it make more sense to use an FPGA and create a giant<br>
> multi-channel 1-Bit DAC?<br>
><br>
> Looking at some Elektron hardware teardowns it appears that they are<br>
> using the latter approach.<br>
><br>
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</blockquote></div></div><span class="gmail_signature_prefix">-- </span><br><div dir="ltr" class="gmail_signature" data-smartmail="gmail_signature">/Jonatan<br><a href="http://kymatica.com" target="_blank">http://kymatica.com</a></div>