[sdiy] Where to buy ceramic caps

[Andre Majorel]

On 2017-12-29 22:51 -0800, rsdio at audiobanshee.com wrote:
> On Dec 29, 2017, at 6:19 PM, David G Dixon <dixon at mail.ubc.ca> wrote:
>
> > I've just laid out a quad opamp relaxation oscillator with
> > four different resistor values (10k, 100k, 1M, 10M) for
> > testing all 12 values of my capacitors to give frequencies
> > in the hundreds of Hz.  The frequency is 1/[2 ln(3) RC], so
> > with this I can quickly and accurately measure the true
> > capacitance (since I don't trust my DVM) and sort into
> > "within 1%" and "not within 1%" piles.  Then I can build my
> > stupid 90 deg PDNs with confidence, and without trimmers.
> 
> Except that after you???ve gone to all of this trouble to sort
> capacitors into ???within 1%??? and ???not within 1%??? piles,
> you???ll find that the manufacturer has already sorted them
> the same way and sold all of the ???within 1%??? caps to
> someone willing to pay more. There will be a gap in your
> measured values, such that the 5% caps will all be >+1% or
> <-1% but none between -1% and +1%. If the capacitor technology
> includes 1%, 5%, and 10% or 1%, 2%, and 5%, then you???ll find
> similar missing gaps in the ranges of measured values.

Even if that's the case, couldn't he use caps that all fall
between, say, -1% and -2% of their nominal value ? Or +3% and
+4%. Or whatever is right for the next E96 value, if the R/C
ratio matters.

-- 
André Majorel http://www.teaser.fr/~amajorel/