HD24/96 Technical Reference

105

Safe Synchronization

Everything you have just learned above can be summarized into a few handy rules and maxims. Recite these rules 20 times each day until they become permanently etched into the neural pathways of your brain.

1.No two clocks ever run at exactly the same speed. Period. This phenomenon of nature cannot be corrected for by living in denial and pretending everything will be OK if you don’t synchronize the clocks.

2.Devices can be correctly synchronized only by matching the speed of their primary timing/drive mechanisms and aligning the position of their transports with respect to time.

3.All synchronization signals used in a setup, including time code, video, and word clock, MUST be resolved to each other. Failure to do so will result in drift between two or more devices in the setup.

4.All digital audio devices that share digital audio signals must be locked together using word clock, superclock, or AES Null. Failure to do so may result in pops and clicks if digital audio paths are connected between various devices. The HDR24/96 has NO self-clocking I/O interfaces. Word clock must be used instead.

5.Free Bonus Factoid: Some digital audio devices have self-clocking interfaces. In other words, the signals that carry the audio also carry a signal from which the sample clock of the unit can be derived. Typically this is true of many devices that are capable of receiving AES, S/PDIF, or ADAT Optical signals. In the case of self-clocking interfaces no additional clock is needed.

6.Time code and video signals are not sample clock signals; word clock, superclock, and AES Null are. Some devices, like the HDR24/96 can resolve their Sample Clock to video. Others can resolve their Sample Clock to time code.

7.When left to choose between using MTC or LTC, use LTC.

8.If a device does not support all six of the standard Time Code Frame Rates, make sure you understand how the nomenclature is used in relationship to these six rates.

9.When doing pull-ups or pull-downs, make sure you understand exactly how the equipment you are using works to avoid the pitfalls of inconsistent nomenclature and methodology.

10.When reading LTC from or feeding LTC to analog tape it is best to use a time code reshaper/regenerator in the signal path. Never use EQ, compression, or noise reduction on LTC.