<html>
<head>
<meta http-equiv="Content-Type" content="text/html; charset=utf-8">
<style type="text/css" style="display:none;"> P {margin-top:0;margin-bottom:0;} </style>
</head>
<body dir="ltr">
<div style="font-family: Calibri, Arial, Helvetica, sans-serif; font-size: 12pt; color: rgb(0, 0, 0); background-color: rgb(255, 255, 255);" class="elementToProof">
I think you mean to say any R/2R based DAC with external reference. Plenty of delta-sigmas have an external reference but won't work like that.</div>
<div style="font-family: Calibri, Arial, Helvetica, sans-serif; font-size: 12pt; color: rgb(0, 0, 0); background-color: rgb(255, 255, 255);" class="elementToProof">
<br>
</div>
<div style="font-family: Calibri, Arial, Helvetica, sans-serif; font-size: 12pt; color: rgb(0, 0, 0); background-color: rgb(255, 255, 255);" class="elementToProof">
So what exactly is the second DAC in your scheme doing ?</div>
<div style="font-family: Calibri, Arial, Helvetica, sans-serif; font-size: 12pt; color: rgb(0, 0, 0); background-color: rgb(255, 255, 255);" class="elementToProof">
<br>
</div>
<div id="appendonsend"></div>
<hr style="display:inline-block;width:98%" tabindex="-1">
<div id="divRplyFwdMsg" dir="ltr"><font face="Calibri, sans-serif" style="font-size:11pt" color="#000000"><b>From:</b> Synth-diy <synth-diy-bounces@synth-diy.org> on behalf of Roman Sowa <modular@go2.pl><br>
<b>Sent:</b> 21 March 2023 10:25<br>
<b>To:</b> Paul Perry <pfperry@melbpc.org.au>; synth-diy@synth-diy.org <synth-diy@synth-diy.org><br>
<b>Subject:</b> Re: [sdiy] Niche ACM-1 how's this thing work?</font>
<div> </div>
</div>
<div class="BodyFragment"><font size="2"><span style="font-size:11pt;">
<div class="PlainText">You can make multiplying DAC out of 2 any DACs with external reference
<br>
input. Both DACs must be controlled by the same SPI. The Vref of 1st DAC <br>
is driven with your input of interest, say mxer's channel audio, but <br>
with added voltage offset to midscale so the signal fits within DAC's <br>
ratings. The Vref of 2nd DAC takes only the offset itself. Then the <br>
output of 2nd DAC is reversed and added to the output of 1st DAC.<br>
Despite the hassle and complexity it's still cheaper than "real" <br>
multiplying DAC.<br>
<br>
Roman<br>
<br>
<br>
<br>
W dniu 2023-03-20 o 23:29, Paul Perry via Synth-diy pisze:<br>
> This reminds me that I can't seem to find any cheap available <br>
> multiplying DACs. Any suggestions? Are they abandoned technology?<br>
> paul perry Melbourne Australia<br>
> <br>
> On Tue, Mar 21, 2023 at 4:12 AM Mike Bryant <mbryant@futurehorizons.com <br>
> <<a href="mailto:mbryant@futurehorizons.com">mailto:mbryant@futurehorizons.com</a>>> wrote:<br>
> <br>
> That was one of Jim Williams' last app notes for Natsemi before he<br>
> left for LTC. At the time the DAC1020 family was an improvement on<br>
> the PMI and ADI devices we used but I recall it was a lot more<br>
> expensive at the time.<br>
> ------------------------------------------------------------------------<br>
> *From:* Ben Stuyts <ben@stuyts.nl <<a href="mailto:ben@stuyts.nl">mailto:ben@stuyts.nl</a>>><br>
> *Sent:* 20 March 2023 16:50<br>
> *To:* Mike Bryant <mbryant@futurehorizons.com<br>
> <<a href="mailto:mbryant@futurehorizons.com">mailto:mbryant@futurehorizons.com</a>>><br>
> *Cc:* synth-diy@synth-diy.org <<a href="mailto:synth-diy@synth-diy.org">mailto:synth-diy@synth-diy.org</a>><br>
> <synth-diy@synth-diy.org <<a href="mailto:synth-diy@synth-diy.org">mailto:synth-diy@synth-diy.org</a>>>; mark<br>
> verbos <markverbos@gmail.com <<a href="mailto:markverbos@gmail.com">mailto:markverbos@gmail.com</a>>><br>
> *Subject:* Re: [sdiy] Niche ACM-1 how's this thing work?<br>
> That reminded me at something I’ve looked at in the past: NatSemi<br>
> AN-299 uses a multiplying DAC (DAC1020) for this. See page 5<br>
> (panner/attenuator) and 6 (bandpass filter) of<br>
> <a href="https://www.ti.com/lit/an/snva530/snva530.pdf">https://www.ti.com/lit/an/snva530/snva530.pdf</a><br>
> <<a href="https://www.ti.com/lit/an/snva530/snva530.pdf">https://www.ti.com/lit/an/snva530/snva530.pdf</a>>.<br>
> <br>
> Ben<br>
> <br>
>> On 20 Mar 2023, at 16:10, Mike Bryant <mbryant@futurehorizons.com<br>
>> <<a href="mailto:mbryant@futurehorizons.com">mailto:mbryant@futurehorizons.com</a>>> wrote:<br>
>><br>
>> The NatSemi LM1973N used to be fairly popular for this<br>
>> application. Not as good as the dBX chip but a lot cheaper and<br>
>> smaller. It was three channel, but there were also one and two<br>
>> channel versions. Maybe they prototyped an 8-channel version but<br>
>> never released it into volume manufacture.<br>
>><br>
>> ------------------------------------------------------------------------<br>
>> *From:*Synth-diy <synth-diy-bounces@synth-diy.org<br>
>> <<a href="mailto:synth-diy-bounces@synth-diy.org">mailto:synth-diy-bounces@synth-diy.org</a>>> on behalf of mark verbos<br>
>> via Synth-diy <synth-diy@synth-diy.org<br>
>> <<a href="mailto:synth-diy@synth-diy.org">mailto:synth-diy@synth-diy.org</a>>><br>
>> *Sent:*20 March 2023 13:55<br>
>> *To:*synth-diy@synth-diy.org <<a href="mailto:synth-diy@synth-diy.org">mailto:synth-diy@synth-diy.org</a>><br>
>> <synth-diy@synth-diy.org <<a href="mailto:synth-diy@synth-diy.org">mailto:synth-diy@synth-diy.org</a>>><br>
>> *Subject:*[sdiy] Niche ACM-1 how's this thing work?<br>
>> Those of us as old as I am might remember this thing from the 90s.<br>
>> It is patched into the inserts on a mixer and then adds MIDI<br>
>> controlled automation. All the chatter around is about how it is<br>
>> passive, so it has “infinite” headroom, 0% distortion, 0% gain. I<br>
>> got one recently for a low price. I looked inside, eager to know<br>
>> the trick…. Vactrols? Motorized pots? something I don’t even know<br>
>> about? Inside the is a big chip 28pins or something with the label<br>
>> scratched off. Does anyone know what is actually going on in this<br>
>> thing? Is that an 8 channel digitally controlled pot? Just curious.<br>
>><br>
>> Mark<br>
>><br>
>><br>
>><br>
>> _______________________________________________<br>
>> Synth-diy mailing list<br>
>> Synth-diy@synth-diy.org <<a href="mailto:Synth-diy@synth-diy.org">mailto:Synth-diy@synth-diy.org</a>><br>
>> <a href="http://synth-diy.org/mailman/listinfo/synth-diy">http://synth-diy.org/mailman/listinfo/synth-diy</a><br>
>> <<a href="http://synth-diy.org/mailman/listinfo/synth-diy">http://synth-diy.org/mailman/listinfo/synth-diy</a>><br>
>> Selling or trading? Use marketplace@synth-diy.org<br>
>> <<a href="mailto:marketplace@synth-diy.org">mailto:marketplace@synth-diy.org</a>><br>
>> _______________________________________________<br>
>> Synth-diy mailing list<br>
>> Synth-diy@synth-diy.org <<a href="mailto:Synth-diy@synth-diy.org">mailto:Synth-diy@synth-diy.org</a>><br>
>> <a href="http://synth-diy.org/mailman/listinfo/synth-diy">http://synth-diy.org/mailman/listinfo/synth-diy</a><br>
>> <<a href="http://synth-diy.org/mailman/listinfo/synth-diy">http://synth-diy.org/mailman/listinfo/synth-diy</a>><br>
>> Selling or trading? Usemarketplace@synth-diy.org<br>
>> <<a href="mailto:marketplace@synth-diy.org">mailto:marketplace@synth-diy.org</a>><br>
> <br>
> _______________________________________________<br>
> Synth-diy mailing list<br>
> Synth-diy@synth-diy.org <<a href="mailto:Synth-diy@synth-diy.org">mailto:Synth-diy@synth-diy.org</a>><br>
> <a href="http://synth-diy.org/mailman/listinfo/synth-diy">http://synth-diy.org/mailman/listinfo/synth-diy</a><br>
> <<a href="http://synth-diy.org/mailman/listinfo/synth-diy">http://synth-diy.org/mailman/listinfo/synth-diy</a>><br>
> Selling or trading? Use marketplace@synth-diy.org<br>
> <<a href="mailto:marketplace@synth-diy.org">mailto:marketplace@synth-diy.org</a>><br>
> <br>
> <br>
> _______________________________________________<br>
> Synth-diy mailing list<br>
> Synth-diy@synth-diy.org<br>
> <a href="http://synth-diy.org/mailman/listinfo/synth-diy">http://synth-diy.org/mailman/listinfo/synth-diy</a><br>
> Selling or trading? Use marketplace@synth-diy.org<br>
_______________________________________________<br>
Synth-diy mailing list<br>
Synth-diy@synth-diy.org<br>
<a href="http://synth-diy.org/mailman/listinfo/synth-diy">http://synth-diy.org/mailman/listinfo/synth-diy</a><br>
Selling or trading? Use marketplace@synth-diy.org<br>
</div>
</span></font></div>
</body>
</html>