[sdiy] A440 Reference using 11MHz clock

[Jaroslaw Ziembicki]

OK, I agree that using synchronous counters is the
*smart* and recommended way...
By the way, I realized I had been wrong (see
my circuit description at the bottom):
- the diodes should be connected in the opposite
   way (cathodes to outputs, anodes to MR's)
- the resistor should be a pull-up to VCC.
Sorry about the mistake.

Regards,
Jarek.



----- Original Message ----- 
From: "James Patchell" <patchell at cox.net>
To: "SDIY" <synth-diy at dropmix.xs4all.nl>
Sent: Sunday, June 27, 2004 7:42 PM
Subject: Re: [sdiy] A440 Reference using 11MHz clock


> The simple way is not always the best way....I prefer to use synchronous 
> counters as they give the cleanest outputs.
> 
> But, to each his own.
> 
> At 07:16 PM 6/27/2004 +0200, Jaroslaw Ziembicki wrote:
> >Hello James and everyone!
> >
> >One simple way to get 440Hz out from 11MHz is to
> >use 2 counters 74HC4040 (CD4040 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%).