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pdcaceo 10th August 2012 04:15 PM

Re-clock application question
 
In CD application. FS=44.1Khz


For example.


CD internal clock is 16.9344Mhz, And then I have a better clock( low jitter, said 1ps) 45.158Mhz(1024FS) or 22.579Mhz(512FS).

Is that possible to reclock 16.9344 by this low jitter clock?

oshifis 10th August 2012 06:39 PM

Reclocking should occur at the signal that controls the D/A conversion, otherwise jitter accumulates again during the digital signal processing between the master clock and the DAC...

DF96 10th August 2012 07:28 PM

The issue here is not reclocking, but synchronisation by injection locking. The ratio between 16.9344 and 45.158 is roughly (but not exactly, 3/8).

If you try to reclock data with a second unsynchronised clock then you are guaranteed to duplicate or drop some samples. This may or may not sound worse than jitter but it is theoretically wrong. To synchronise the clocks together you either need a PLL or injection locking.

pdcaceo 11th August 2012 12:51 AM

Quote:

Originally Posted by oshifis (Post 3121878)
Reclocking should occur at the signal that controls the D/A conversion, otherwise jitter accumulates again during the digital signal processing between the master clock and the DAC...




In fact, I don't have much idea.

I have seem many design to reclock at CDP SPDIF and inside DAC.


MY intention is using one clock to sync all equipment.


FOr example, using DAC clock to feedback to CD player 16.9344Mhz( old philips player)

pdcaceo 11th August 2012 12:54 AM

Quote:

Originally Posted by DF96 (Post 3121931)
The issue here is not reclocking, but synchronisation by injection locking. The ratio between 16.9344 and 45.158 is roughly (but not exactly, 3/8).

If you try to reclock data with a second unsynchronised clock then you are guaranteed to duplicate or drop some samples. This may or may not sound worse than jitter but it is theoretically wrong. To synchronise the clocks together you either need a PLL or injection locking.



What is injection locking?

ANy PLL design can take a reference?


IT seems JVC K2 and tentlab tentlink is this approch

DF96 11th August 2012 09:51 AM

Injection locking is injecting a small signal (usually harmonic or sub-harmonic) into an oscillator to force it to lock to the external signal.

PLL is the other way to lock two oscillators together. A PLL can either directly lock one oscillator to another one, or it can lock to a data stream; up to the designer what he wants.

If you want to lock all your equipment together, like a professional setup, then that may be possible but expect to do a lot of reading and designing because normal domestic equipment is not designed to take external clock inputs. Much amateur 're-clocking' is just a trivial exercise in getting things wrong, but not realising this.

pdcaceo 13th August 2012 01:24 PM

Hi DF96,


Yes, I want to lock all equipment.

I have a Esotric G03X word clock and my CDP is "Chord" with word clock input. However my Chord DAC64 don't have the word clock input.

However, I found that now a day, many DAC has word clock input.

So, it is possible to make a DAC with word clock input?


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