From: Daniel Nilsson <[EMAIL PROTECTED]> Subject: Re: gEDA-user: Difficulty in border areas Date: Thu, 6 Jan 2005 19:57:58 -0500 Message-ID: <[EMAIL PROTECTED]>
> > d) What if I want to make 44.1kHz from say 33MHz and need it > > super-hyper-roxx0r stable because am using it for feeding Hi-Fi audio DAC > > and > > even the tiniest jitter would be audible? How do I do it with PLL? > > Sorry, don't know much about audio design... I do know that all PLL > circuits will have jitter though, there is no such think as a zero > jitter PLL that I've ever heard of. Zero-jitter does simply not exist. You can have sufficiently low jitter, but that is another thing. Zero-jitter oscillators/PLLs is really like the holy grail, everyone wants them but they just can't be found. Now, assuming you have a low jitter oscillator of the right frequency, then you either divide down the reference frequency, the output frequency or both to create the input signals to the phase comparator. The output of the phase comparator is then filtered through a loop filter and that gives you the control voltage to the oscillator. A good phase comparator, a good loop gain and loop filter gets you the right benefits of the long term stability from the reference and the short term stability of the oscillator. It's just a little magical touch in choosing the phase comparator and loop filter parameters. There's books on this. The best book isn't the book by Best, but it is still lot of valuable information in there. Besides, most A/D and D/As run off from higher frequencies as I recall it. Cheers, Magnus
