[sdiy] Black Magic oscillator cans

[John L Marshall]

Crystals can be trimmed to an exact frequency with a small variable
capacitor, either in series or parallel.

Take care,
John
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Pacific Northwest Synthesizer Meeting

DATE CHANGE: August 2, 2003

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----- Original Message ----- 
From: "Glen" <mclilith at charter.net>
To: "Tim Ressel" <madhun2001 at yahoo.com>; "Synth-Diy"
<synth-diy at dropmix.xs4all.nl>
Sent: Sunday, July 20, 2003 9:41 AM
Subject: Re: [sdiy] Black Magic oscillator cans


> At 05:56 AM 7/20/03 , Tim Ressel wrote:
>
> >Does anyone have experince with programmable
> >oscillators? ECS and Cardinal make these little
> >oscillators that look like normal clock oscillators,
> >but are programmable.
>
> I just visited the ECS web site and viewed the data sheets for a few of
> these devices. I also viewed the page about the dedicated programmer you
> would need to program these devices. Considering the need for a
programmer,
> it seems somewhat expensive to get started with these devices, if you only
> need to program one or two it's going to be too expensive, but if you are
> doing thousands it wouldn't be bad.
>
> There is one thing that bothers me even more than needing a programmer. I
> could not find any reference to the *Precision* with which these devices
> could be programmed. I could only find reference to the frequency ranges
> they would operate over. For example, if I want an oscillator set to
> 2.00024 MHz, can I actually program that particular frequency? It's
> possible that the closest frequency you could program would be 2.0002 MHz;
> or even worse, 2.000 MHz might be the closest frequency this device
> provides for. I would definitely want to know how fine I could adjust the
> frequency before I got into working with these devices.
>
> If all you want is to feed a TOG, why not do what has been done
> commercially for several years. Use an LC oscillator containing a variable
> inductor. These can be fairly stable, and they have the advantage of being
> *continuously* tunable. This is especially handy if you have more than one
> TOG in an instrument and you want to detune one very slightly from the
> other one.
>
> If you really want crystal stability, wouldn't it be fairly simple to have
> some custom crystals made? There are crystal houses that do this sort of
> thing all the time. I don't think it costs all that much, and it will
> probably provide you with even more stability and less jitter than these
> programmable devices. I know that most of the typical fixed-frequency
> crystal oscillators are not quite as accurate or stable as a good discrete
> crystal oscillator design, using a high-quality crystal.
>
>
> later,
> Glen Berry
>
>