Ensuring all the machines are running at the same speed is a fundamental to all recording sessions. Where at all possible we lock tape machines, digital recorders and video decks to our house video reference. This results in all machines locking to the same video frame edge. Failing this (or where situations dictate) we use wordclock or AES. Internal references are very rarely used.
At AIR Studios we run a pair of Trilogy Mentor digital SPGs (Sync Pulse Generators). They are configured as master and slave, the master providing the ultimate 10MHz clock from which all references are derived. This enables us to provide 25fps (PAL), 29.97fps (NTSC) & true 30fps (Black & White) black & burst video references, as well as 44.1KHz & 48KHz wordclock & AES references. Since they all have a common master clock we can run ANY combination with no drifting, e.g. PAL and NTSC on the same session if required. All signals are distributed via Pro-Bel distribution amplifiers throughout the studio.
The studios use Timeline Lynx synchroniser modules. We rate these as the worlds most accurate and reliable units for all tape synchronisation.
Analogue tape machines MUST be resolved and locked to a video reference if you wish to transfer audio to and from a hard disk system such as Protools. The hard disk system must also have the same reference signal. If the audio on the tape machine starts in time with the hard disk, then drifts out over time, check all machines are correctly referenced. However if it was recorded without a common reference the only chance of sync is to re-use the same equipment used at the time of transfer and hope for the best.
When striping analogue tape it's synchroniser MUST be offline or "wild". The code track will be on input when you record. An online the synchroniser will attempt to resolve the machine to the code. This will result in, possibly huge, speed variations on the tape deck.
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