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<div class="moz-cite-prefix">On 4/9/21 1:45 AM, David G Dixon via
Synth-diy wrote:<br>
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<blockquote type="cite"
cite="mid:7210D61E08D74E90B6EC32EBACA75EB3@david78c70950b">
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<div><font size="2" face="Arial"><span class="741353706-09042021">Hey
Team,</span></font></div>
<div><font size="2" face="Arial"><span class="741353706-09042021"></span></font> </div>
<div><font size="2" face="Arial"><span class="741353706-09042021">So,
I've now got a ton of orders for my little two-Dome-filter
frequency shifter, which I've figured out how to build in
euro format (12HP, if you're curious). I hand select all
the film capacitors for the Dome filters so that they all
have the same (or nearly so) mantissas -- I try to get them
either all within 0.2%, or 0.4% at worst. My phase
displacement simulation tells me that this gives very nearly
perfect results.</span></font></div>
<div><font size="2" face="Arial"><span class="741353706-09042021"></span></font> </div>
<div><font size="2" face="Arial"><span class="741353706-09042021">Anyway,
I ran low on capacitors to the point where I couldn't put
together decent collections for the 18-stage filter (I need
4 102s, 4 103s, 4 104s, and 6 105s for it). I bought 250
each of the smaller values and 200 of the 105s. Tonight I
measured all of the 105s, thinking that they would ideally
form a Gaussian distribution around 1.000uF. Well, they
were nearly all clustered between about 1.030uF and 1.050uF,
and in fact, about 20% of them were off spec (higher than
1.050uF, and these are 5% caps). Not a single one of them
was less than 1.020uF. They are Kemet caps. So now I've
got to hope that the other values also tend on the high side
of their tolerance ranges, or else I'm going to have to buy
even more caps.</span></font></div>
<div><font size="2" face="Arial"><span class="741353706-09042021"></span></font> </div>
<div><font size="2" face="Arial"><span class="741353706-09042021">I
think I've given myself a fool's errand here.</span></font></div>
<div><font size="2" face="Arial"><span class="741353706-09042021"></span></font> </div>
<div><font size="2" face="Arial"><span class="741353706-09042021">Cheers,</span></font></div>
<div><font size="2" face="Arial"><span class="741353706-09042021">Doc
Sketchy</span></font></div>
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<p>Eee... what's up Doc?</p>
<p>Of all of the Rs and Cs I've matched, I've never seen that bell
curve land right on the stated value. Especially with capacitors.
It's always been some point over or under within tolerance.</p>
<p>Would it be easier to take, say 4 1.03uF caps and nudge any
frequency determining resistors up/down as needed?</p>
<p>- Oren<br>
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