Jitter Reduction through Reclocking Units - what is the best Approach ??

Status
Not open for further replies.
Jump to Latest
#21
DF96 said:
CD players usually run at x1 speed, so the data comes off the disc at approximately the right speed. It is placed in a FIFO buffer, and read out using a crystal clock. The motor speed is locked to the crystal, but of course will vary a little. The motor servo will try to keep the buffer about half-full. The quality of the transport has an indirect effect on sound: poor focussing or track following means more work for the error correction to do with the potential for interpolation, poor PSU design or poor grounding can mean noise gets where it shouldn't. If working correctly, the transport has no direct effect on the sound as it simply has to deliver correct data at roughly the right speed.

It may be that some newer or cheaper units work more like a computer, with a fast drive and a massive buffer, but fast transports tend to be noisy.
Click to expand...

Sounds sensible to me.
 
#22
DF96 said:
CD players usually run at x1 speed, so the data comes off the disc at approximately the right speed.
Click to expand...

I knew there was something I had to say about that... I've finally remembered that some 'CD Walkmen' (remember them?) used to have a switch for 'anti-skip'. I used to wonder why anyone wouldn't want it on anti-skip all the time, and the answer was that it ran the CD faster so that it could have several goes at reading it while being shaken about. Maybe there were other differences too. I think the reason you wouldn't want it on that setting all the time was that it ran the battery down faster.

The motor speed is locked to the crystal, but of course will vary a little.
Click to expand...

This may be true, but I don't see any real reason why it has to be (see above). I've noticed that when a CD is dirty or scratched, a player sometimes seems to have several tries without the audio stream being interrupted - or am I just thinking of CD ROM drives..?
 
#23
tiefbassuebertr said:
By follow URLs and in the attached files you will find various schematic of reclocking units in front of the DAC IC.
I don't understand the individual pros and cons.
At first look the russian approach seems to be the best solution.
But I am not really sure.
Which of this examples is to prefer?

Digital decoding of biphase-mark encoded serial digital signals
Reproduction equipment for digital audio
Click to expand...

I am still looking for those reclock variation with best sonic quality - follow I know:
http://sergeysvs.narod.ru/projects/Clocking/clocking2.html
http://www.hagtech.com/pdf/hagdac.pdf
PRBSªº­µÅT¶é¦a
High End Audio - Digital decoder for NOS DAC

which I should prefer ?
 
#24
It does not need to be overcomplicated. You don't need to reclock all signal lines, only the single one that controls the conversion (usually WS of the I2S lines). I use an SN74S74N for reclocking. This IC is not available any longer, you can find it in very old digital boards. But the master clock should be perfect, otherwise it does not make any improvement.
 
Status
Not open for further replies.
Top Bottom