Here’s another angle on our recent thread (see inSync 1/29/99 and 1/20/99) about digital clocks. This comes from one of our friends at Indiana University:
I just wanted to respond to a recent reply regarding internal and external sync on a DAW. From an “in the trenches” point of view, this is one of the most common causes of errors in our studio. Someone copies a DAT digitally into Pro Tools at 44.1…the digital input option automatically switches to external sync…the student finishes recording and takes his DAT out of the machine (say a Panasonic SV3800)…the DAT player’s clock reverts to 48 kHz. The student’s file plays back, not with weird unmistakable glitches, but about a whole tone off, the difference in sampling rates. I get about 20 phone calls a week, and try to train my students to immediately return the hardware setting to internal sync, so this may not be as dismisable a problem as it sounded from the column.
Editor’s Note: Agreed, this is a valid point. Some DAT machines do have default sample rates they jump to when no DAT is inserted. The tip from 1/29/99 was more in reference to powering machines down or otherwise taking them “off-line.” There are other solutions for your problem though. In the SV-3800, for example, the sample rate can be set so it defaults to 44.1, which will solve this problem for most situations (assuming most people are working at 44.1).
The important point, however, and the bottom line, is that anytime we press play or record on a digital machine we should always know what the clock source is. It is something that runs through my mind every single time I initiate recording or playback on any digital system. What is my clock source? When the clock source is some other machine, it then becomes important to ask what its clock source is. Always know the real source of the clock all the time and life is much easier in the digital world.