[sdiy] A440 Reference using 11MHz clock

[Jaroslaw Ziembicki]

Hello James and everyone!

One simple way to get 440Hz out from 11MHz is to
use 2 counters 74HC4040 (CD40404 is too slow!).
Connect 11MHz to CP(10) of counter1, Q11(1) of
counter1 to CP(10) of counter2. Then connect each
of the following pins:
counter1:  5,2,13,12
counter2:  7,6
through a diode (eg. 1N4148) to MR(11) of both chips.
Each diode is connected with the anode to the counter output
and with the cathode to both MR's. Also, put a pull-down
resistor (about 10 k) between both MR's and GROUND.
So you get a cheap, simple frequency divider.
The output is: counter2 pin 6.
It's possible to have another crystal frequencies and just use
another counters' outputs. Example for 10MHz:
counter1:  9,7,6,4,13,1
counter2:  9,6
output: counter2 pin 6
The output frequency is 440.0052801 Hz
(relative error = +0.0012%).

Regards
Jarek


----- Original Message ----- 
From: "James Patchell" <patchell at cox.net>
To: <synth-diy at dropmix.xs4all.nl>
Sent: Sunday, June 27, 2004 6:23 PM
Subject: [sdiy] A440 Reference using 11MHz clock


> http://www.oldcrows.net/~patchell/div25000.pdf