BACKGROUND
INFORMATION
The math used to generate the values above comes
courtesy of the Audio Engineering Society June 1979 issue - Vol. 27
#6. S. Lipshitz is the author of the fine article covering
nearly every type of equalizer circuit including pre-emphasis, de-emphasis,
passive and active circuits. Though the math seems complicated,
a little study and patience reveals that it is really just a ratio of time
constants. I have used the spreadsheet in all my designs and the accuracy is
spot on. The only concerns are to be sure that the driving amplifier A1 has a
low enough output impedance relative to R1 and that the following amplifier A2
has an input impedance of at least 50 times R1 to prevent loading.
You can enter data for R1 and for the 3 frequency
settings. Those frequencies represent corner frequencies of the 3 stages of the
curve, the low end, the mid and the treble. If you have a different curve you
would like to equalize, simply input the frequencies of interest and the
spreadsheet will give you the component values. |