[sdiy] A-440 Reference Oscillator update

[phillip m gallo]

Dave,

An 11MHz Xtal makes generation pretty easy.

regards,
p


-----Original Message-----
From: owner-synth-diy at dropmix.xs4all.nl
[mailto:owner-synth-diy at dropmix.xs4all.nl]On Behalf Of David Brown
Sent: Tuesday, May 23, 2006 9:02 PM
To: synth diy
Subject: [sdiy] A-440 Reference Oscillator update


Thanks for all the replies. It looks like there is interest in having
at least one batch of parts and PCB.  I'm going to do a bit more work
on this. One email indicated that I could get even closer in
frequency (e.g. exact) by starting with a 5.0688 MHz crystal.  I'm
going to give it a try and see how well it works. I have some parts
on order that will be here in a couple of weeks.

I'm also going to redo the interface to the Max7401 filter.  I'm
driving it rail to rail and minimum distortion is at something like
4V pk-pk.  I've got a nice little circuit to attenuate and center the
440 Hz clock and would like to give it a try to minimize THD.  I
prototyped a similar circuit and want to experiment more with this.

I'll keep all of your emails and give you an update when I try out
the modifications.

Dave


At 04:41 PM 5/19/2006, David Brown wrote:
>There was some discussion here a while ago on the need for an A-440
>reference oscillator.  I made mine with a Clare M-991 call progress
>tone generator.  It works well but they are hard to find.  I decided
>to design one around an Atmel AVR processor / switched filter that
>produces a square and sine wave output.  Here's a link to the project:
>http://modularsynthesis.com/a440/A440.htm
>
>So the question ... is there any interest from this group?
>
>Would you be interested in a programmed IC?
>Would you be interested in a small PCB?
>Would you be interested in the filter IC?
>
>Let me know.  I'm done with the project and have looked into the
>possibility of parts or PCBs if there is sufficient interest.
>
>I detail some of the math on the web page. The accuracy of this is
>well below that of tuning by ear and better than most home test
>equipment to measure it.  Parts cost should be pretty low and only
>requires a couple of external components.

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