The Architect
Model 500 & Model 700
Installer’s Guide
Appendix B
Appendix B - Building Your Own PFM Modules
AudioControl PFM filters use resistor modules for frequency
programming. All modules are constructed in the same way, with
the exception of the actual value of the resistors used. In each
module, ALL resistor values are equal. The resistor value for any
given frequency is chosen according to the following equation:
Resistor (kilohms) = 7200
÷
frequency (Hz)
Example: To find the resistors needed for 1000 Hz.
R (kilohms) = 7200
÷
1000
R (kilohms) = 7.2
R = 7.2 K = 7200 ohms
Building Modules
PFM modules require 6 resistors mounted on a 14-pin DIP
header. In the 14-pin modules, the middle resistor position is
unused and may be left unconnected. We recommend 5% ¼ watt
carbon film resistors, or if you really want to be spot-on, 1%
metal-film resistors (difficult to get).
The DIP headers are available from Radio Shack or other
electronic parts distributors. Radio Shack seems to carry more
16-pin headers than 14-pin, so you may have to manufacture a 14-
pin unit by cutting off the last 2 pins. It will make things easier if
you buy a 16-pin IC socket as well. You can chuck the socket in
your vise and have a handy fixture to hold the header while you
solder.
Do not be confused by the modules from the factory that do
not show individual resistors. They really are there, just encased in
plastic.
Standard Module Frequencies
18dB/octave (14 pin)
Frequency
20 Hz
25 Hz
35 Hz
40 Hz
45 Hz
50 Hz
60 Hz
65 Hz
70 Hz
80 Hz
90 Hz
Frequency
100 Hz
120 Hz
130 Hz
150 Hz
170 Hz
200 Hz
270 Hz
350 Hz
500 Hz
725 Hz
950 Hz
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Note: Center Resistor is absent
Summary of Contents for Architect 500
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