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Tweaks for systems, rooms and Do It Yourself (DIY) help. FAQ.

Loop filter for CS8414 (wildfunkyspecs?)

Hey Daryl:

YMMV theory/practice disclaimer here, I have stuck to the 8412 as I have no 96 kHZ sources. Waiting for the format wars to settle down a bit. All other factors equal, the laws of Physics and economics do favor a narrower range VCO however.

The 0.047uF / 1K values are stock databook values for the 8412...does the MSB link you have use the 8412 or the 8414?
Crystal [ the chip house, not the crack house ] data sheets for the 8414 show 0.068uF / 470R values, with a bit of jitter peaking, which is generally not a good thing, particularly with a second order loop.
Although *theoretically* out of band stuff can be ignored, ie jitter above 44 kHZ, in practice it has a nasty habit of splattering, intermodulating, folding down into the audible arena, so upping the loop to third order while avoiding peaking is a good thing. This is essential if using a JISCO jitter scrambler/decorrelator.
Adding a small cap, typically in the range of one hundredth the value +/- of the existing cap from the filt pin to the adjacent analog ground pin will usually do the trick.

Except for soldering and ESD damage, different loop components won't hurt/break the chip; if it (1) locks to a datastream and (2) sounds better then you on the right track. Listen for reduced glare and increased "reality quotient" to use subjectivese.

For the 8414 I would try starting values of 270R, 0.2/0.22 uF, and 2200/3300 pF. Presuming it locks, I would try different values of the resistor, 220R, 240R, 270R, 300R and stick with the smallest one that sounds good.

Do post results. I don't expect as spectacular results as with the 8412, but we could get lucky...

Watching the power meter unwind,

WMS


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