"Phil Allison" wrote in message

"Arny Krueger"

Capacitance is only significant when its impedance
within the audible range is less than 10 times any
parallel resistance. Three relevant resistances are 13K
(the approximate maximum input impedance of a mic pre
with phantom power), 2 K (the approximate input
impedance of many mic preamps, and 600 ohms. I did a little spread sheet
and came up with the
following capacitances for 20 KHz and the three
resistances: 600 ohms 0.066314561 uF
2,000 ohms 0.019894368 uF
13,000 ohms 0.003060672 uF


** All WILDLY wrong numbers !!

That is true. Thanks for the general correction.

The "correct" values a

1320 pF, 390 pF and 60 pF.

almost, see below.

C = 1 / ( 2. pi. F. R )

You forgot the factor of 10 in your equation, Phil.

The true equation is:

C = 1 / ( 20 * pi * F * R )

Your math may be off a tad as well, as I get:

1326 pF, 398 pF and 61 pF.

I'll put my money on the error being in your estimation of Pi.

But thanks for the check-out. ;-)