#2 - hkborn :

Two articles from Grimm worth reading, one on atomic clock; the other on jitter. Funny though, even he has launched his CC1 clock, he still think that an external clock may not always give better sound. What an honest man!!
http://www.grimmaudio.com/whitepapers/PLL%20and%20clock%20basics.pdf
http://www.grimmaudio.com/whitepapers/Picoseconds%20or%20ppm.pdf

#4 - hkborn :

If a Dac is good, then it's clock must be good also, so no need for external clock.
External clock is more useful when doing recording and mixing where a number of digital sources are involved.
For music playback where only one digital source is involved, a good dac is more than enough!!Remember data transmission does not need a clock!!

#6 - hkborn :

jitter appears not just on digital music, but also on other digital source like video. Grimm also has VCC for conversion of video, use along with CC1.

#8 - 長長影子 :

Oh, Simon Woollard was my classmate.

#10 - batmanames04 :

would you recommend Weiss the next weiss medea +++ to have a world clock input???

#12 - Kuro :

Unfortunately, these so called industry experts still have no idea that long term clock accuracy has nothing to do with jitter (short term accuracy).

An atomic clock buys you long term accuracy. But in audio, we need short term timing accuracy - the correct timing on the rising edge of the biphase S/PDIF signal. Atomic clock with its low ppm design is not the ideal clock for audio. To make matter worse, the use of an external clock divider to divide down a 10MHz clock signal to one that is suitable for audio will increase the jitter further on the clock signal.

A proper clock design would use a high Q x'tal with a clock circuit that does not degrade the Q value of the x'tal. That means internal clock, not external clock. An atomic clock cannot achieve phase noise of -140dbC/Hz at 100Hz, where a high Q x'tal internal clock design can. A good internal clock is not only way cheaper, but also way better than an external clock. The trick is how to find this high Q x'tal and how to design this clock circuit.

The external clock is only useful for sycn'ing multiple digital devices/sources. It is not really useful for playback or even ADC, unless the internal clock in your playback device or ADC is crap.

And finally, Async USB / Firewire does not work the same as sending back the clock line from the DAC to the transport. These asyn devices buffer the audio data and reclock the audio data using its own internal clock.

#14 - homantin :

Very enlightening comments.
But there are loads of +ve comments re master clocks.... 20~30% better...spatial ... musical... etc
Could it be just mix-n-match improvement?

#16 - homantin :

oic. Thx for explanation. I'll keep my$$$ for other toys.

#18 - odysseyhk :

If CAS output to DAC using async USB interface, external clock only use as replacement of the internal clock if the internal clock quality is not good enough. See many ching's post in this thread.