Sure, the bigger is the Q factor of an oscillator, the less tunable it is.
Its tunability depends also on the resonance mode number, actual material, the way it was cut and G-d knows what else. Look at the following analogy: you have, say, parallel LC loop with VERY stable L and C. Then you are saying: "OK, I need to change the resonance frequency of this Lc loop, so I'll add a voltage-controlled Ctune in parallel with C, so the resulting capacitance would be C + Ctune, and the resulting resonance frequency would be 1 / (2 * PI * sqrt(L * (C + Ctune))). Now, if you want to tune the loop, why did you pay a lot of money for very stable, high quality and expensive L and primary C in the first place ? Since changes of Ctune are much greater than natural C instability, the only thing natural C (in)stability is the ranges of fine tuning. If the range of tuning due to Ctune is much greater than possible drift due natural instability of C, the stability of C doesn't matter. The stable LC loop is the XTAL in the above analogy. On Mon, 2 Jan 2006 22:25:41 +0100 fons adriaensen <[EMAIL PROTECTED]> wrote: > On Mon, Jan 02, 2006 at 06:09:17PM +0200, Sergei Steshenko wrote: > > > In other words, tunable xtal is a bad xtal by definition. > > There are no such things as 'tunable' and 'untunable' xtals. > *Every* xtal behaves has a parallel or series LC circuit near > resonance (depending on how it's used) and can be detuned by > adding some capacitance. That by itself does not make it less > stable. > > Even PLLs are often implemented using a VCXO (voltage controlled > xtal oscillator). You get the stability of the external reference, > and outside the loop bandwidth, the quality of an xtal. Standard > practice in all sorts of telecomm equipment, and the stability > requirements there are orders of magnitude more strict than for > audio. > > -- > FA > > > ------------------------------------------------------- This SF.net email is sponsored by: Splunk Inc. Do you grep through log files for problems? Stop! Download the new AJAX search engine that makes searching your log files as easy as surfing the web. DOWNLOAD SPLUNK! http://ads.osdn.com/?ad_id=7637&alloc_id=16865&op=click _______________________________________________ Alsa-user mailing list Alsa-user@lists.sourceforge.net https://lists.sourceforge.net/lists/listinfo/alsa-user
