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That was one of Jim Williams' last app notes for Natsemi before he left for LTC. At the time the DAC1020 family was an improvement on the PMI and ADI devices we used but I recall it was a lot more expensive at the time.<br>
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<div id="divRplyFwdMsg" dir="ltr"><font face="Calibri, sans-serif" style="font-size:11pt" color="#000000"><b>From:</b> Ben Stuyts <ben@stuyts.nl><br>
<b>Sent:</b> 20 March 2023 16:50<br>
<b>To:</b> Mike Bryant <mbryant@futurehorizons.com><br>
<b>Cc:</b> synth-diy@synth-diy.org <synth-diy@synth-diy.org>; mark verbos <markverbos@gmail.com><br>
<b>Subject:</b> Re: [sdiy] Niche ACM-1 how's this thing work?</font>
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<div class="" style="word-wrap:break-word; line-break:after-white-space">That reminded me at something I’ve looked at in the past: NatSemi AN-299 uses a multiplying DAC (DAC1020) for this. See page 5 (panner/attenuator) and 6 (bandpass filter) of <a href="https://www.ti.com/lit/an/snva530/snva530.pdf" class="">https://www.ti.com/lit/an/snva530/snva530.pdf</a>.
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<div class="">Ben<br class="">
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<div class="">On 20 Mar 2023, at 16:10, Mike Bryant <<a href="mailto:mbryant@futurehorizons.com" class="">mbryant@futurehorizons.com</a>> wrote:</div>
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The NatSemi LM1973N used to be fairly popular for this application. Not as good as the dBX chip but a lot cheaper and smaller. It was three channel, but there were also one and two channel versions. Maybe they prototyped an 8-channel version but never released
it into volume manufacture.<br class="">
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<font face="Calibri, sans-serif" class="" style="font-size:11pt"><b class="">From:</b><span class="x_Apple-converted-space"> </span>Synth-diy <<a href="mailto:synth-diy-bounces@synth-diy.org" class="">synth-diy-bounces@synth-diy.org</a>> on behalf of mark verbos
via Synth-diy <<a href="mailto:synth-diy@synth-diy.org" class="">synth-diy@synth-diy.org</a>><br class="">
<b class="">Sent:</b><span class="x_Apple-converted-space"> </span>20 March 2023 13:55<br class="">
<b class="">To:</b><span class="x_Apple-converted-space"> </span><a href="mailto:synth-diy@synth-diy.org" class="">synth-diy@synth-diy.org</a> <<a href="mailto:synth-diy@synth-diy.org" class="">synth-diy@synth-diy.org</a>><br class="">
<b class="">Subject:</b><span class="x_Apple-converted-space"> </span>[sdiy] Niche ACM-1 how's this thing work?</font>
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<div class="x_PlainText">Those of us as old as I am might remember this thing from the 90s. It is patched into the inserts on a mixer and then adds MIDI controlled automation. All the chatter around is about how it is passive, so it has “infinite” headroom,
0% distortion, 0% gain. I got one recently for a low price. I looked inside, eager to know the trick…. Vactrols? Motorized pots? something I don’t even know about? Inside the is a big chip 28pins or something with the label scratched off. Does anyone know
what is actually going on in this thing? Is that an 8 channel digitally controlled pot? Just curious.<br class="">
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Mark<br class="">
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