<html><head><meta http-equiv="Content-Type" content="text/html; charset=us-ascii"></head><body style="word-wrap: break-word; -webkit-nbsp-mode: space; line-break: after-white-space;" class="">Missing the 64th, 128th, 192nd, 256th harmonic (etc) but otherwise identical. The 64th harmonic is -36dB down so it's probably audible but hardly a big deal. In my view, it's close enough for synthesis - this is raw material, not a pure test signal. Is it rich and does it provide plenty to work with? Yep!<div class="">The Roland Alpha Juno "DCO" chip (NCO really) does the same thing, but manages to produce an 8-bit staircase, which reduces the errors even further. No-one ever complained the "Hoover" synth wasn't producing a rich enough waveform!<br class=""><div class=""><br class=""><div><br class=""><blockquote type="cite" class=""><div class="">On 6 Jul 2026, at 23:27, Mike Bryant <<a href="mailto:mbryant@futurehorizons.com" class="">mbryant@futurehorizons.com</a>> wrote:</div><br class="Apple-interchange-newline"><div class=""><div class="elementToProof" style="font-style: normal; font-variant-caps: normal; font-weight: normal; letter-spacing: normal; text-align: start; text-indent: 0px; text-transform: none; white-space: normal; word-spacing: 0px; -webkit-text-stroke-width: 0px; text-decoration: none; font-family: Aptos, Aptos_EmbeddedFont, Aptos_MSFontService, Calibri, Helvetica, sans-serif; font-size: 12pt;">Ah right. Not really a proper sawtooth then. Thanks</div><div class="elementToProof" style="font-style: normal; font-variant-caps: normal; font-weight: normal; letter-spacing: normal; text-align: start; text-indent: 0px; text-transform: none; white-space: normal; word-spacing: 0px; -webkit-text-stroke-width: 0px; text-decoration: none; font-family: Aptos, Aptos_EmbeddedFont, Aptos_MSFontService, Calibri, Helvetica, sans-serif; font-size: 12pt;"><br class=""></div><div id="appendonsend" style="caret-color: rgb(0, 0, 0); font-family: Helvetica; font-size: 12px; font-style: normal; font-variant-caps: normal; font-weight: normal; letter-spacing: normal; text-align: start; text-indent: 0px; text-transform: none; white-space: normal; word-spacing: 0px; -webkit-text-stroke-width: 0px; text-decoration: none;" class=""></div><hr tabindex="-1" style="caret-color: rgb(0, 0, 0); font-family: Helvetica; font-size: 12px; font-style: normal; font-variant-caps: normal; font-weight: normal; letter-spacing: normal; text-align: start; text-indent: 0px; text-transform: none; white-space: normal; word-spacing: 0px; -webkit-text-stroke-width: 0px; text-decoration: none; display: inline-block; width: 609.546875px;" class=""><span style="caret-color: rgb(0, 0, 0); font-family: Helvetica; font-size: 12px; font-style: normal; font-variant-caps: normal; font-weight: normal; letter-spacing: normal; text-align: start; text-indent: 0px; text-transform: none; white-space: normal; word-spacing: 0px; -webkit-text-stroke-width: 0px; text-decoration: none; float: none; display: inline !important;" class=""></span><div id="divRplyFwdMsg" dir="ltr" style="caret-color: rgb(0, 0, 0); font-family: Helvetica; font-size: 12px; font-style: normal; font-variant-caps: normal; font-weight: normal; letter-spacing: normal; text-align: start; text-indent: 0px; text-transform: none; white-space: normal; word-spacing: 0px; -webkit-text-stroke-width: 0px; text-decoration: none;" class=""><font face="Calibri, sans-serif" style="font-size: 11pt;" class=""><b class="">From:</b><span class="Apple-converted-space"> </span>Tom Wiltshire <<a href="mailto:tom@electricdruid.net" class="">tom@electricdruid.net</a>><br class=""><b class="">Sent:</b><span class="Apple-converted-space"> </span>06 July 2026 23:25<br class=""><b class="">To:</b><span class="Apple-converted-space"> </span>Mike Bryant <<a href="mailto:mbryant@futurehorizons.com" class="">mbryant@futurehorizons.com</a>><br class=""><b class="">Cc:</b><span class="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>>; Roman Sowa <<a href="mailto:modular@go2.pl" class="">modular@go2.pl</a>><br class=""><b class="">Subject:</b><span class="Apple-converted-space"> </span>Re: [sdiy] GRP Genesi</font><div class=""> </div></div><div class="" style="caret-color: rgb(0, 0, 0); font-family: Helvetica; font-size: 12px; font-style: normal; font-variant-caps: normal; font-weight: normal; letter-spacing: normal; text-align: start; text-indent: 0px; text-transform: none; white-space: normal; word-spacing: 0px; -webkit-text-stroke-width: 0px; text-decoration: none; word-wrap: break-word; line-break: after-white-space;">Isn't it just the typical adding-up-a-load-of-octave-squarewaves to make a staircase "ramp" waveform? 6 bits in this case, iirc.<div class=""><br class=""></div><div class="">Ah, yes, here it is, from the service manual:</div><div class=""><br class=""></div><div class=""><span id="cid:2AE7EC16-6057-40DC-8334-B1FA2C776868"><PastedGraphic-8.png></span><br class=""><div class=""><br class=""><blockquote type="cite" class=""><div class="">On 6 Jul 2026, at 13:01, Mike Bryant <<a href="mailto:mbryant@futurehorizons.com" class="">mbryant@futurehorizons.com</a>> wrote:</div><br class="x_Apple-interchange-newline"><div class=""><div class="x_elementToProof" style="font-style: normal; font-variant-caps: normal; font-weight: normal; letter-spacing: normal; text-align: start; text-indent: 0px; text-transform: none; white-space: normal; word-spacing: 0px; text-decoration: none; font-family: Aptos, Aptos_EmbeddedFont, Aptos_MSFontService, Calibri, Helvetica, sans-serif; font-size: 12pt;">Actually one of the cleverest bits is probably converting the down-scaled squarewaves to sawtooths whilst keeping the levels consistent across the whole frequency range. No mention of how they did they - presumably by programming a constant current source with the key and octave number ?</div><div id="x_appendonsend" class="" style="font-family: Helvetica; font-size: 12px; font-style: normal; font-variant-caps: normal; font-weight: normal; letter-spacing: normal; text-align: start; text-indent: 0px; text-transform: none; white-space: normal; word-spacing: 0px; text-decoration: none;"></div><hr tabindex="-1" class="" style="font-family: Helvetica; font-size: 12px; font-style: normal; font-variant-caps: normal; font-weight: normal; letter-spacing: normal; text-align: start; text-indent: 0px; text-transform: none; white-space: normal; word-spacing: 0px; text-decoration: none; display: inline-block; width: 609.546875px;"><span class="Apple-converted-space"> </span><span class="" style="font-family: Helvetica; font-size: 12px; font-style: normal; font-variant-caps: normal; font-weight: normal; letter-spacing: normal; text-align: start; text-indent: 0px; text-transform: none; white-space: normal; word-spacing: 0px; text-decoration: none; float: none; display: inline !important;"></span><span class="Apple-converted-space"> </span><div id="x_divRplyFwdMsg" dir="ltr" class="" style="font-family: Helvetica; font-size: 12px; font-style: normal; font-variant-caps: normal; font-weight: normal; letter-spacing: normal; text-align: start; text-indent: 0px; text-transform: none; white-space: normal; word-spacing: 0px; text-decoration: none;"><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 Roman Sowa 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>06 July 2026 12:06<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><span class="Apple-converted-space"> </span><<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>Re: [sdiy] GRP Genesi</font><div class=""> </div></div><div class="x_BodyFragment" style="font-family: Helvetica; font-size: 12px; font-style: normal; font-variant-caps: normal; font-weight: normal; letter-spacing: normal; text-align: start; text-indent: 0px; text-transform: none; white-space: normal; word-spacing: 0px; text-decoration: none;"><font size="2" class=""><span class="" style="font-size: 11pt;"><div class="x_PlainText">At first glimpse, just looking at block diagram, it looks like typical<span class="x_Apple-converted-space"> </span><br class="">PLL, but instead of phase comparator it uses F-to-V conversion and<span class="x_Apple-converted-space"> </span><br class="">voltage comparator. Same divider ratio is used in the feedback as in the<span class="x_Apple-converted-space"> </span><br class="">vaweform output, so the VCO works only within 1 octave while overall<span class="x_Apple-converted-space"> </span><br class="">output spans over many octaves.<br class=""><br class="">Roman<br class=""><br class="">W dniu 2026-07-05 o 11:26, Neil Johnson via Synth-diy pisze:<br class="">> Michael E Caloroso wrote:<br class="">><span class="x_Apple-converted-space"> </span><br class="">> US 3,930,429<br class="">><span class="x_Apple-converted-space"> </span><br class="">><span class="x_Apple-converted-space"> </span><br class="">> Don did a write-up of it here:<span class="x_Apple-converted-space"> </span><br class="">><span class="x_Apple-converted-space"> </span><a href="https://till.com/articles/arp/patents.html#US03930429" class="">https://till.com/articles/arp/patents.html#US03930429</a><span class="x_Apple-converted-space"> </span><br class="">> <<a href="https://till.com/articles/arp/patents.html#US03930429" class="">https://till.com/articles/arp/patents.html#US03930429</a>><br class="">> Very weird architecture indeed!<br class="">><span class="x_Apple-converted-space"> </span><br class="">> Neil<br class="">><span class="x_Apple-converted-space"> </span><br class="">> ________________________________________________________<br class="">> This is the Synth-diy mailing list<br class="">> Submit email to:<span class="Apple-converted-space"> </span><a href="mailto:Synth-diy@synth-diy.org" class="">Synth-diy@synth-diy.org</a><br class="">> View archive at:<span class="x_Apple-converted-space"> </span><a href="https://synth-diy.org/pipermail/synth-diy/" class="">https://synth-diy.org/pipermail/synth-diy/</a><br class="">> Check your settings at:<span class="x_Apple-converted-space"> </span><a href="https://synth-diy.org/mailman/listinfo/synth-diy" class="">https://synth-diy.org/mailman/listinfo/synth-diy</a><br class="">> Selling or trading? 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