Alesis ADAT - Affordable Digital Multitrack (part 11)
Wow and flutter
There is no such thing as a perfectly flat surface, a perfectly round shaft or a perfectly spherical ball bearing. Its also impossible to align two cylinders so they are perfectly concentric. The result of this is that the tape machine that runs at an absolutely steady speed will never exist. In the analogue world this matters because tape speed has a direct bearing on pitch. Slow variations in speed cause wow, faster ones cause flutter. A digital machine will not run at a perfectly constant speed either, but since the data can be read into a buffer memory and then be clocked out with the accuracy of a crystal oscillator, it doesnt matter at all if the mechanics are slightly wobbly (within specification of course).
Timecode is to recording engineers what spots are to teenagers, and sometimes we forget that unlike spots, timecode does indeed have a few benefits. But when your synchroniser wont synchronise, or your sequencer drops out of record at the wrong moment then you will be snarling and cursing and wondering why you hadnt taken up a career as an interior decorator. If you have ever look at raw timecode on an oscilloscope, straight from the tape machine, then you wont be at all surprised that you get the occasional troublesome moment. In fact if you look at a steady 1kHz sine wave replayed from tape you will be amazed that recordings of music sound anything like the real thing. Even on a good tape recorder the sine wave will be bobbing up and down like a dinghy crossing the wake of the Isle of Wight ferry - and make that the QE2 when the head gets worn. But if your timecode is recorded onto digital tape, as described in the main text, then it will be absolutely rock solid and almost as clean as when it was fresh out of the generator. The low cost timecode readers usually found associated with MIDI sequencers will particularly appreciate this.
What did your mother tell you when you were small? - Never record important parts on the edge tracks! Of course we all know this, but the problem is that you dont always know how a piece of music is going to develop and sooner or later, when all the tracks are full, the producer is bound to say, Lets ditch the castanets (which are on track 1) and put down this important vocal counterpoint Ive just thought of. Or words to that effect. If you use an analogue multitrack Ill ask you the question, How good are your edge tracks? Try recording stereo music on tracks 1 and 2 and play back on headphones. If your heads are at all worn you will hear image shift and drop outs on track 1. Since ADAT is a rotary head recorder it cant be said to have an edge track in the normal sense so you can be sure that each track will have identical performance within infinitesimally small margins.