"Rich Andrews" wrote in message
.44
Stig Erik Tangen wrote in
:
TUBELOVER wrote:
I have a solid state phono preamp which has a 50 micro farad
electrolytic capacitor in series with the preamp signal at the very
output of the preamp. i wish to replace this cap with a film cap.
what is the minimum value cap i can use and still have a response
that is not rolled off due to too low a value? the phono preamp
will feed a line amp with a minimum of 10000 ohms input resistance.
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rg
1 uF into 10kOhms load equals approx 16 Hz -3 dB. 1 uF or more should
work.
F(-1 dB) of 20 Hz is a common standard. This requires a 1.6 uF cap for a
standard 10K line level load. I'd recommend more like 2 uF.
If this is for driving power amps, there are power amps with input impedance
that is more like 5K, so now a 3-5 uF cap seems to be in order. If you have
really good subwoofer, 10 uF might make sense.
What is the formula for this?
F(-3 dB) = 1/(2*pi*R*C)
R in ohms, C in Farads
For high pass:
F(-1 dB) = 2* F(-3)
F(-0.1 dB) = 6.666* F(-3)