<div dir="ltr">With low voltage rails you might run into trouble with resonant state variable filters, where the passband remains constant but the resonant band is boosted with increasing resonance.<div><br></div><div>MC</div></div><br><div class="gmail_quote"><div dir="ltr" class="gmail_attr">On Fri, Jan 14, 2022 at 6:44 AM 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;border-left-color:rgb(204,204,204);padding-left:1ex">
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<p class="MsoNormal"><span style="font-size:11pt;font-family:Calibri,sans-serif;color:rgb(31,73,125)">Yeah :-)<u></u><u></u></span></p>
<p class="MsoNormal"><span style="font-size:11pt;font-family:Calibri,sans-serif;color:rgb(31,73,125)"><u></u> <u></u></span></p>
<p class="MsoNormal"><span style="font-size:11pt;font-family:Calibri,sans-serif;color:rgb(31,73,125)">Not really sure what people have against digital nowadays as you can model any sound you want accurately in digital. If you want a particular distortion, just
model it. Far easier than playing with random biases on obsolete transistors trying to get a particular nuance to the sound.
<u></u><u></u></span></p>
<p class="MsoNormal"><span style="font-size:11pt;font-family:Calibri,sans-serif;color:rgb(31,73,125)"><u></u> <u></u></span></p>
<p class="MsoNormal"><span style="font-size:11pt;font-family:Calibri,sans-serif;color:rgb(31,73,125)">Cost is usually always lower as well. Somebody showed a design with the STM32H750 the other day which I often use, and if you need about ten times that processing
power the Pi CM4 range (when available) gives you almost 10 billion 64 bit instructions/second.<u></u><u></u></span></p>
<p class="MsoNormal"><span style="font-size:11pt;font-family:Calibri,sans-serif;color:rgb(31,73,125)"><u></u> <u></u></span></p>
<p class="MsoNormal"><span style="font-size:11pt;font-family:Calibri,sans-serif;color:rgb(31,73,125)">I guess it’s just the maths that scares people off.<u></u><u></u></span></p>
<p class="MsoNormal"><span style="font-size:11pt;font-family:Calibri,sans-serif;color:rgb(31,73,125)"><u></u> <u></u></span></p>
<p class="MsoNormal"><span style="font-size:11pt;font-family:Calibri,sans-serif;color:rgb(31,73,125)"><u></u> <u></u></span></p>
<p class="MsoNormal"><span style="font-size:11pt;font-family:Calibri,sans-serif;color:rgb(31,73,125)"><u></u> <u></u></span></p>
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<p class="MsoNormal"><b><span lang="EN-US" style="font-size:10pt;font-family:Tahoma,sans-serif">From:</span></b><span lang="EN-US" style="font-size:10pt;font-family:Tahoma,sans-serif"> Tom Wiltshire [mailto:<a href="mailto:tom@electricdruid.net" target="_blank">tom@electricdruid.net</a>]
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<b>Sent:</b> 14 January 2022 11:28<br>
<b>To:</b> Mike Bryant<br>
<b>Cc:</b> cheater cheater; cheater cheater via Synth-diy<br>
<b>Subject:</b> Re: [sdiy] Low voltage synthesis?<u></u><u></u></span></p>
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<p class="MsoNormal"><u></u> <u></u></p>
<p class="MsoNormal">Fantastic! Even less chance of any noise!<u></u><u></u></p>
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<p class="MsoNormal"><u></u> <u></u></p>
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<p class="MsoNormal">So Cheater is looking for ways to do low voltage audio with low noise and distortion, and all the examples we're finding are...digital!?! It's not really a surprise, is it?<u></u><u></u></p>
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<p class="MsoNormal">On 14 Jan 2022, at 11:19, Mike Bryant <<a href="mailto:mbryant@futurehorizons.com" target="_blank">mbryant@futurehorizons.com</a>> wrote:<u></u><u></u></p>
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<p class="MsoNormal"><span style="font-size:11pt;font-family:Calibri,sans-serif;color:rgb(31,73,125)">Cut out the middle bit :-)</span><u></u><u></u></p>
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<p class="MsoNormal"><span style="font-size:11pt;font-family:Calibri,sans-serif;color:rgb(31,73,125)"> </span><u></u><u></u></p>
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<p class="MsoNormal"><a href="https://www.rohm.com/products/audio-video/audio-amplifiers/speaker-amplifiers/bd28623muv-product" target="_blank"><span style="color:purple">BD28623MUV</span></a><u></u><u></u></p>
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<p class="MsoNormal"><span style="font-size:11pt;font-family:Calibri,sans-serif;color:rgb(31,73,125)">These modulate the PDM directly from the I2S input, so there’s no analogue on-chip at all.</span><u></u><u></u></p>
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<p class="MsoNormal"><span style="font-size:11pt;font-family:Calibri,sans-serif;color:rgb(31,73,125)"> </span><u></u><u></u></p>
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<p class="MsoNormal"><span style="font-size:11pt;font-family:Calibri,sans-serif;color:rgb(31,73,125)">TI, ST, NXP and Infineon have similar parts for different power levels.</span><u></u><u></u></p>
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<p class="MsoNormal"><span style="font-size:11pt;font-family:Calibri,sans-serif;color:rgb(31,73,125)"> </span><u></u><u></u></p>
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<p class="MsoNormal"><span style="font-size:11pt;font-family:Calibri,sans-serif;color:rgb(31,73,125)"> </span><u></u><u></u></p>
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<p class="MsoNormal"><b><span lang="EN-US" style="font-size:10pt;font-family:Tahoma,sans-serif">From:</span></b><span class="gmail-m_-5047858634224061158apple-converted-space"><span lang="EN-US" style="font-size:10pt;font-family:Tahoma,sans-serif"> </span></span><span lang="EN-US" style="font-size:10pt;font-family:Tahoma,sans-serif">Tom
Wiltshire [<a href="mailto:tom@electricdruid.net" target="_blank">mailto:tom@electricdruid.net</a>]<span class="gmail-m_-5047858634224061158apple-converted-space"> </span><br>
<b>Sent:</b><span class="gmail-m_-5047858634224061158apple-converted-space"> </span>14 January 2022 10:27<br>
<b>To:</b><span class="gmail-m_-5047858634224061158apple-converted-space"> </span>cheater cheater; cheater cheater via Synth-diy<br>
<b>Cc:</b><span class="gmail-m_-5047858634224061158apple-converted-space"> </span>Mike Bryant<br>
<b>Subject:</b><span class="gmail-m_-5047858634224061158apple-converted-space"> </span>Re: [sdiy] Low voltage synthesis?</span><u></u><u></u></p>
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<p class="MsoNormal"> <u></u><u></u></p>
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<p class="MsoNormal">I'd guess:<u></u><u></u></p>
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<p class="MsoNormal"> <u></u><u></u></p>
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<p class="MsoNormal">DAC -> Class D amp -> Outside world.<u></u><u></u></p>
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<p class="MsoNormal"> <u></u><u></u></p>
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<p class="MsoNormal">Not a lot of scope for noise in that very short signal chain.<u></u><u></u></p>
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<p class="MsoNormal"> <u></u><u></u></p>
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<p class="MsoNormal">On 13 Jan 2022, at 23:45, cheater cheater via Synth-diy <<a href="mailto:synth-diy@synth-diy.org" target="_blank"><span style="color:purple">synth-diy@synth-diy.org</span></a>> wrote:<u></u><u></u></p>
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<p class="MsoNormal"> <u></u><u></u></p>
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<p class="MsoNormal"><span style="font-size:9pt;font-family:Helvetica,sans-serif">I wonder what's being used in places like<br>
mobile phones or wireless earbuds for example, they can't be running<br>
+/-5V op amps or LV op amps with major crossover distortion.</span><u></u><u></u></p>
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<p class="MsoNormal"><u></u> <u></u></p>
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