“I’ve been building and configuring my new digital studio for a few months now and thanks to past Tech Tip issues have become very informed about things like word clock and other issues germane to my studio. I just bought a good master clock generator and one of my problems is the need to distribute that signal among various pieces of gear. I know there are products made for that, but now my question: A friend tells me I can simply use a cheap little $100 video distribution amp for this. Some of the audio products, which appear to be the same thing, cost substantially more. Is this extra expense really necessary?”
Yes, it is. I can see how a video DA would “look” like it can do the same job: It has the same BNC connectors, and the frequency response is about the same (though not quite) as the digital audio DA. Before even getting in to why this box won’t work for digital audio, let’s step back a bit and look at it for video. Do you honestly think a professional video house uses a $100 video DA? The answer is no. High quality video distribution is substantially more expensive than this. Those high quality units might be okay for digital audio, but it’s very unlikely something this inexpensive is up to the task.
In this case I’m going to avoid getting in to nauseating technical detail because I think the crux of the issue is probably covered in the paragraph above. Keep in mind that these low cost video boxes are designed to distribute an analog video signal. A digital audio signal is made up entirely of square waves. Square waves are extraordinarily difficult for analog electronics to reproduce accurately, and it gets exponentially more difficult as frequency goes up. Of course, an analog video signal also has square waves, but these waves can stand to have their edges rounded off a little bit without seriously compromising the quality of the video. A pro video house wouldn’t stand for it, but in casual use it isn’t that big of a deal. With digital audio timing is critical, which is why you were smart to buy a high quality clock source. If you run that source through a device that’s designed with the tolerances of analog video in mind, those precious edges of the square waves may be rounded just enough to introduce significant jitter into your clock, more than negating the investment you made in the high quality clock to begin with. So we don’t recommend it. Stick with hardware that’s designed for the job at hand. Given the thousands of dollars you have invested in your studio, it’s a pretty insignificant amount of money to spend to really do this last piece right.