<html><head></head><body>What you're interested in is the MATCHING between
the resistors, not the absolute values. Your meter may have a .1% to .5%
error, but it's likely to be pretty much the same error when you measure
two resistors close in value.<br>
If you measure the SAME resistor over and over again, do you get the same
reading? If so, your matching measurement accuracy will be better than your
absolute resistance measurement accuracy.<br>
<br>
<br>
*Star Project wrote:<br>
<blockquote type="cite" cite="mid:NDBBIPNCMLLFKKOLMKFAAEFBCDAA.ampe@swipnet.se"><pre wrap="">Yes its a pretty good idea easuring the resistors<br>to match their values as harry said.<br>But, as a newbie one doesnt very often have access<br>to such precise equipment I know my own Ohmmeter<br>has an error of 0.1% and maybe .5% on the last digit.<br>A pretty cheap way to solve this is however to do<br>as I did when I needed the 16 matched 200K resistors<br>for my TB-303 project. I simply bought them from<br>reichelt in germany (I know shipping suxx to Sweden but<br>they were so much cheaper on other things that I ordered<br>a great deal from them)<br>They were 0.1% and 1/4 W and costs about 0.8 DM which<br>is about 0.4$. Not to cheap when compared to a ordinary<br>resistor but its mostly worth it instead of buying<br>multiple resistors and sit down to hand match.<br><br>By the way my door is allways open for SAD 4096<br>chips for sale.<br><br>/ Andreas H<br><br><br>-----Ursprungligt meddelande-----<br>Från: <a class="moz-txt-link-abbreviated" href="mailto:owner-synth-diy@node12b53.a2000.nl">owner-synth-diy@node12b53.a2000.nl</a><br>[<a class="moz-txt-link-freetext" href="mailto:owner-synth-diy@node12b53.a2000.nl">mailto:owner-synth-diy@node12b53.a2000.nl</a>]För harry<br>Skickat: den 7 januari 2001 04:28<br>Till: Philip<br>Kopia: Peter van Hamersveld; Synth-DIY<br>Ämne: Re: newbees keep on asking questions......<br><br><br>Hey Bees !!!<br><br>The resistors that go to a CV input usually connect to something called a<br>summing amplifier. Complex explanation... but each input resistor is<br>separate<br>from every other one, and the currents (not voltages) are added together.<br><br>VCO's for keyboard use must be ultra precise. You will hear 5% of a<br>half step (C-C#) as grossly out of tune.... so you either<br><br>1) Dedicate one input for Keyboard control, and calibrate the VCO using that<br>input. It will be right on... the others will be close.<br><br>2) Get a real good ohmmeter, and match 1% par
ts to 0.1%. Think of<br>99.5K, 99.6K, 99.7K, 99.8K... I spread out a sheet of paper on the table...<br>with the values written on it. And measure each resistor until I have enough<br>that<br>match. Don't take long but you need a lot of candidates...<br><br>Now those resistors don't have to be "100K" exactly... as long as they are<br>the<br>same value. Then when you calibrate, you will null out the error, and you<br>can use any<br>input for KCV.<br><br>The meter reading (in circuit) goes off when the voltage that the ohmmeter<br>sends through<br>the resistor is enough to turn on some semiconductor junction, a diode,<br>transistor, etc.<br>If this is the cause... reversing the meter leads will often chage the<br>value.<br><br>Some meters have special voltages for testing with or without activating<br>unwanted junctions...<br><br>Its best to use the meter to try and measure voltages when you are in<br>circuit. Usually<br>this will cause the circuit to screw up. Sample and Hold circuits, and some<br>points<br>of an oscillator or filter may be exceptions...<br><br>H^) harry (keep at it!)<br><br>Philip wrote:<br><br></pre>
<blockquote type="cite"><pre wrap="">1.The Key Cv often have a scale pot. So you can trim the settings more<br></pre></blockquote>
<pre wrap=""><!---->than the other inputs<br></pre>
<blockquote type="cite"><pre wrap="">however you can use it as normal input or not even include it.you can also<br></pre></blockquote>
<pre wrap=""><!---->input key cv in other cv inputs (doh).<br></pre>
<blockquote type="cite"><pre wrap="">2. Instead of having a bunch of multiples you can hook them up instead<br></pre></blockquote>
<pre wrap=""><!---->directly into the vco, and normaly there is also couple resistors that acts<br>like a cv ,mixer.Oftern you can leave some of the inputs out(not all doh)<br></pre>
<blockquote type="cite"><pre wrap="">3. I guess there is something that divides,multiplies<br>ect it varies,,,,,,,,,,,,<br>// Olsson<br>----- Original Message -----<br>From: "Peter van Hamersveld" <a class="moz-txt-link-rfc2396E" href="mailto:peter83@bigfoot.com"><peter83@bigfoot.com></a><br>To: <a class="moz-txt-link-rfc2396E" href="mailto:synth-diy@node12b53.a2000.nl"><synth-diy@node12b53.a2000.nl></a><br>Sent: Saturday, January 06, 2001 9:19 PM<br>Subject: newbees keep on asking questions......<br><br></pre><blockquote type="cite"><pre wrap="">yess, here some questions again from Peter and Egbert<br><br>1) why do some VCO's have both a [KEY CV] and a [CV] input part?<br><br>2) why do some of them have multiple [CV] input parts?<br><br>3) how come that one we connect a (e.g) 100K Ohm resistor to a circuit,<br></pre></blockquote></blockquote>
<pre wrap=""><!---->it reads about 60K when we measure it resistance IN the circuit, and there<br>are no obvious illegal connections? is this usual?<br></pre>
<blockquote type="cite"><blockquote type="cite"><pre wrap="">well, that's it for this time i guess, other questions will follow<br></pre></blockquote></blockquote>
<pre wrap=""><!---->undoubtly.....<br></pre>
</blockquote>
<br>
<pre class="moz-signature">--
Scott Bernardi
<a class="moz-txt-link-abbreviated" href="mailto:sbernardi@home.net">sbernardi@home.net</a></pre>
<br>
</body></html>