[time-nuts] Sound Cards for locking to GPSDO 10 MHz references

Magnus Danielson magnus at rubidium.dyndns.org
Tue Jun 2 03:43:34 EDT 2009


Brian Kirby skrev:
> I use a Lynx One sound card, it has analog and digital I/O and MIDI I/O 
> and clock I/O.  Their manuals are available on line at 
> www.lynxstudio.com.  These are profession 24 bit cards, the analog I/O 
> uses balanced interfaces.  They handle AES/EBU and SP DIF digital audio 
> formats.
> 
> The sound card can take an internal clock, an external clock input on 
> the MIDI port, there is a parallel clock header on the PC board, and a 
> digital clock input on the digital audio lines.
> 
> It can accept a 13.5 Mhz video dot clock, a 27 Mhz video dot clock, and 
> a word clock and word clock/256.

13,5 MHz is ITU-R BT.601/BT.656 luminance sampling rate.
27 MHz is BT.601/BT.656 luminance/chroma-difference combined sampling 
rate (4:2:2).

27 MHz is the video reference rate of them all. Sad that they broke it 
when they did the North American HD stuff. Breaking numerology like that 
isn't very nice... it always cost extra now.

I think you mean word-clock * 256 as this is Digidesign/ProTools clock 
distribution strategy, giving 12,288 MHz for 48 kHz sampling rate.

Cheers,
Magnus




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