What is more steady? A mediocre internal crystal implementation is going to outdo even a good external clock implementation.īut there are times and reasons to use external clocks. There is some circuitry in there that keeps comparing the incoming external clock rate to the VCXO, and makes the proper adjustment on an ongoing basis… Unlike the internal clock (fixed crystal case), you have a crystal that can be pulled up or down by some amount, we call it a VCXO (voltage controlled crystal oscillator). At this point, you have accumulated a lot more jitter (I can list half a dozen causes). Now you have to go through some electronic circuit to receive the clock. What happens when you get a stand alone “almost no jitter clock”? You look AT THE OUTPUT CONNECTOR of that “super clock box” and it generally can work as well as the internal crystal clock Now take a cable and hook it to the AD chassis. You now have a low jitter clock inside the machine. The best way to clock a converter is with internal clock, using a good fundamental frequency crystal (third order types are more jittery), and locating the crystal properly (good ground to the AD ample hold and so on). In fact, any converter which does not perform equally as good or BETTER on internal clock than external is also defective. An external clock is a bandaid for a "cure" which can only be done properly within a good converter design. If you hear differences when you change clocks "controlling" your converters, then you have a defective converter design! A well-designed converter should contain internal phase locked loops whose performance reduces any incoming jitter artifacts to inaudibility. Dat machines, stand alone cd writers, outbord fx)ĭan is the man! And this is what I bet he'll tell you! Also, how do you control digital units with no dedicated word clock input?(i.e. One unit gives me a great clear 3d image while another is quite smeared and more 2D.Ĭan you please tell me why this is happening and what the best possible scenario is to set up a central word clock distribution and how to get the best results. ![]() ![]() I've been experimenting with different word clock scenarios in our facility and am dumbfounded by the sonic differences of just changing which unit is the clock master. Man, I really appreciate you joining the forum. Big Bri wrote on Sat, 02 October 2004 03:08
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