702T/744T Digital Inputs and Time Code
When using the 702T or 744T AES/EBU digital inputs and the built in time code generator to sync the recorders from a mixer with digital outputs, care must be taken. The 702T and 744T internal time code generator can only run off of its internal high-accuracy crystal - it does not use word clock or AES/EBU to derive time code. For accurate Broadcast Wave time stamps to be written, it is essential that both the time code generator and the sampling clock (word clock) to be derived from the same clock source, since the time stamp in a Broadcast WAV file is generated from the sample count. Thus, in a WAV file, samples and time stamp cannot be separated. When using the digital input(s) and using the 702T and 744T's internal time code generator, significant drift will certainly occur because the time code and word clock will be referenced to two separate time bases,
- the 7-Series recorder's crystal and
- the external mixer's crystal.
- Connect the Lockit time code output to the 702T/744T time code input.
- Set the recorders to external time code mode.
- Connect the Lockit word clock output to the digital mixer word clock input.
- Run the AES/EBU outputs from the digital mixer into the 744T or 702T.