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[The Resonater]

Is there a device that lets you input several different clock devices and choose which clock to send out of that device?

For instance.

I own a pair of Lavry golds and an Apogee AD16x.  Guy comes in and says, "I want to clock the Lavry's to the Apogee clock" or "I want to clock the Apogee to the Lavry clock" or "I want to use my Rosendahl clock".  Without getting behind all of the devices and move a bunch of cables, is there a box to handle "clock switching and distribution"?

Thanks again, posters...

[danlavry]

The Resonater wrote on Sun, 29 May 2005 19:03

Is there a device that lets you input several different clock devices and choose which clock to send out of that device? For instance. I own a pair of Lavry golds and an Apogee AD16x.  Guy comes in and says, "I want to clock the Lavry's to the Apogee clock" or "I want to clock the Apogee to the Lavry clock" or "I want to use my Rosendahl clock".  Without getting behind all of the devices and move a bunch of cables, is there a box to handle "clock switching and distribution"? Thanks again, posters...

In an ideal world, I do not think that "a guy coming in" should be saying what clock needs to be hooked to what AD. The decision should be based on what setup makes for less jitter at the AD's.

The first rule:
Whenever possible, use internal clock. You may have to use external, when synchronizing more AD's that can be contained within one chassis, but "all things equal", you end up with more jitter when using external clocks.

Placing a good low jitter clock inside the AD chassis, next to the AD converters, is the best you can do. If you place the same circuit in another chassis, you will end up with a lot more jitter, because the clock to AD connection contains a driver, cable, receiver and a PLL circuit, all adding jitter.

Whenever you use clock switching and distribution, you are getting away from internal clocks into the cables and PLL world. A good PLL circuit can help a lot but will be a step down from internal clocking, thus a compromise of jitter for more channels.

Also, an external clock can never fix your AD jitter problems because it does not know what is needed inside the AD box.
My doctor can not help me if he lives in a different state and I do not talk to him ever. The same thing for external clocks and AD's: The AD does not send the clock box ANY INFORMATION about what it needs to be improved. The cable between clock and AD is for sending a clock FROM the clock TO the AD. No information goes from AD to the clock.

But if you still need clock distribution and switching, there are many comments in my bag. But it will be a long writeup, so I will stop for now.

Regards
Dan Lavry  
www.lavryengineering.com

[John L Rice]

The Resonator,

While it's fairly expensive, the Little Labs digital audio router is pretty close to what you need :
http://www.littlelabs.com/digirr.html

I have one but I use it to route digital audio around.  It's nicely thought out and very well constructed.

While this device 'might' work as is to distribute word clock you should talk to Johnathan Little first and tell him what you need. ( he is very freindly and does custom work ) I'd think that you'd only want 4 or 5 inputs ( 4 on the back and one on the front for 'guest' clocks ) and then just a couple outs ( one on back, one on the front ).  And have it so it's speced for 75 ohm ( as is it's 110 ohm for AES signals )

Best of luck!