[sdiy] A440 Reference using 11MHz clock

[James Patchell]

There is at least one mistake in my circuit...the A440 should come off the 
C pin...you won't get anything out of the D pin :-)

At 09:06 PM 6/27/2004 +0200, Jaroslaw Ziembicki wrote:
>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%).
>

         -Jim
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