<html><head><meta http-equiv="Content-Type" content="text/html; charset=utf-8"></head><body style="word-wrap: break-word; -webkit-nbsp-mode: space; line-break: after-white-space;" class="">Thanks all.<div class=""><br class=""></div><div class="">Perhaps Brian is right, and I should just use a single ADC input at the master uP and then send the data via the comms link. After all, vibrato isn’t that fast, so it wouldn’t imply a super-fast sampling frequency. It seems like software might be a better answer than hardware for this one.</div><div class=""><br class=""></div><div class="">Thanks,</div><div class="">Tom</div><div class=""><br class=""></div><div class=""><div class="">
<div style="word-wrap: break-word; -webkit-nbsp-mode: space; -webkit-line-break: after-white-space;" class=""><div style="color: rgb(0, 0, 0); font-family: Helvetica; font-size: 12px; font-style: normal; font-variant-caps: normal; font-weight: normal; letter-spacing: normal; orphans: auto; text-align: start; text-indent: 0px; text-transform: none; white-space: normal; widows: auto; word-spacing: 0px; -webkit-text-stroke-width: 0px;">==================<br class=""> Electric Druid<br class="">Synth & Stompbox DIY<br class="">==================</div></div>
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<div><br class=""><blockquote type="cite" class=""><div class="">On 30 Apr 2018, at 20:49, ASSI <<a href="mailto:Stromeko@nexgo.de" class="">Stromeko@nexgo.de</a>> wrote:</div><br class="Apple-interchange-newline"><div class=""><div class="">On Monday, April 30, 2018 5:14:51 PM CEST Tom Wiltshire wrote:<br class=""><blockquote type="cite" class="">So - I need to tie together several ADC inputs. Can I just tie them<br class="">together? Should I drive the tied-together-inputs with an op-amp follower<br class="">or something to make sure I’ve got a nice low impedance output? Or do the<br class="">inputs themselves need buffers in front of them (e.g. tied-together-signal<br class="">-> opamp buffer -> ADC input). Has anyone tried anything like this?<br class=""></blockquote><br class="">The datasheet should have some details what kind of signal conditioning the <br class="">particular ADC is expecting, but it's usually a bad idea to just tie together <br class="">multiple ADC inputs unless you can make sure they don't sample at the same <br class="">time. Most ADC inputs present a time-dependent impedance that can be quite <br class="">low at the sampling point. Also if capacitive sampling is used (very likely <br class="">these days), the paralleled input capacitances will influence each other and <br class="">degrade the ADC performance significantly. At the minimum and only if your <br class="">actual source is already reasonably low-impedance I'd put an isolation network <br class="">in front of each input (RC lowpass is the most simple one). An actual buffer <br class="">amplifier is better, but you might need an auto-zero buffer for your <br class="">application to get rid of offset voltages.<br class=""><br class=""><br class="">Regards,<br class="">Achim.<br class="">-- <br class="">+<[Q+ Matrix-12 WAVE#46+305 Neuron microQkb Andromeda XTk Blofeld]>+<br class=""><br class="">Wavetables for the Terratec KOMPLEXER:<br class=""><a href="http://Synth.Stromeko.net/Downloads.html#KomplexerWaves" class="">http://Synth.Stromeko.net/Downloads.html#KomplexerWaves</a><br class=""><br class=""><br class=""><br class=""><br class="">_______________________________________________<br class="">Synth-diy mailing list<br class="">Synth-diy@synth-diy.org<br class="">http://synth-diy.org/mailman/listinfo/synth-diy<br class=""></div></div></blockquote></div><br class=""></div></body></html>