Timecode or MIDI Clock
- Thou shalt not have multiple clock
masters. No two clocks ever run at exactly the same speed. This phenomenon of
nature cannot be corrected by living in denial and pretending everything
will be OK if you don't synchronize the clocks.
- Devices can be correctly synchronized
only by matching the speed of the primary timing/drive mechanism and aligning
the position of their transports with respect to time and the primary mechanism,
i.e. timecode and word clock master.
- 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
- 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.
- Addendum to previous rule: Some digital
audio devices have self-clocking interfaces. In other words, the sample clock of
the unit (for locking digital audio devices) can be derived from the signals
that carry the digital audio. 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.
- Timecode and video signals are not sample
clock signals; word clock, superclock, and AES Null are. Some devices, like the
HDR24/96 can derive their Sample Clock from video. Others can derive and even
slew their Sample Clock from timecode.
- When left to choose between using MTC or
LTC, use LTC. Having said that - MTC is more than accurate enough and sometimes
it's just easier to use MTC even when LTC is available.
- 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. The use of time code
terms on that device may differ from other devices in your studio.
- When doing timecode 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.
- When reading LTC from 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.