[sdiy] Niche ACM-1 how's this thing work?

Paul Perry pfperry at melbpc.org.au
Mon Mar 20 23:29:25 CET 2023


This reminds me that I can't seem to find any cheap available multiplying
DACs. Any suggestions? Are they abandoned technology?
paul perry Melbourne Australia

On Tue, Mar 21, 2023 at 4:12 AM Mike Bryant <mbryant at futurehorizons.com>
wrote:

> 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.
> ------------------------------
> *From:* Ben Stuyts <ben at stuyts.nl>
> *Sent:* 20 March 2023 16:50
> *To:* Mike Bryant <mbryant at futurehorizons.com>
> *Cc:* synth-diy at synth-diy.org <synth-diy at synth-diy.org>; mark verbos <
> markverbos at gmail.com>
> *Subject:* Re: [sdiy] Niche ACM-1 how's this thing work?
>
> 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 https://www.ti.com/lit/an/snva530/snva530.pdf.
>
> Ben
>
> On 20 Mar 2023, at 16:10, Mike Bryant <mbryant at futurehorizons.com> wrote:
>
> 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.
>
> ------------------------------
> *From:* Synth-diy <synth-diy-bounces at synth-diy.org> on behalf of mark
> verbos via Synth-diy <synth-diy at synth-diy.org>
> *Sent:* 20 March 2023 13:55
> *To:* synth-diy at synth-diy.org <synth-diy at synth-diy.org>
> *Subject:* [sdiy] Niche ACM-1 how's this thing work?
>
> 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.
>
> Mark
>
>
>
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