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The End of Analogue - Is analogue multitrack recording dead? (part 3)

A post by David Mellor
Thursday January 01, 2004
The problems with analogue multitracks include: crosstalk, counter slippage, drop outs, drop out gaps, edge track quality, end of reel runoff, gap scatter, head misalignment, head feedback, high frequency squashing, line up problems, reel scrape, modulation noise, noise, noise reduction problems, phase distortion, print through, record crosstalk, timecode problems, wow and flutter...
The End of Analogue - Is analogue multitrack recording dead? (part 3)

Analogue Failings

The problems with analogue recorders are too numerous to describe fully, but let me list some of them and explain the most troublesome in more detail. The problems with analogue multitracks include: crosstalk, counter slippage, drop outs, drop out gaps, edge track quality, end of reel runoff, gap scatter, head misalignment, head feedback, high frequency squashing, line up problems, reel scrape, modulation noise, noise, noise reduction problems, phase distortion, print through, record crosstalk, timecode problems, wow and flutter. Is this a long enough list? The biggest problem with analogue recording, in my opinion, is wow and flutter. Wow and flutter - a singular problem with two audible effects - is caused by manufacturing inaccuracies in the tape transport components on a microscopic scale. These inaccuracies cause the speed of the recorder to vary causing either an audible wobble in pitch (wow) or a general dirtying of the sound (flutter). I once had a problem in this area with my multitrack that took a while to solve, and in the meantime my ears became so attuned to the phenomenon that I can now clearly hear W&F on machines that measure within their specifications. Sampled piano and acoustic guitar are the worst instruments for showing it up. The other most major problem with analogue is the general dirtiness of the sound, caused by noise, modulation noise (noise that comes and goes according to the level of the signal) and drop outs. I suggested a simple tone test for digital recorders earlier, so here’s one for analogue multitracks: record a 1kHz sine wave tone at 0dB on one of the edge tracks. (On any machine the edge tracks are usually worse than the others because the head to tape contact is not as reliable). Now play it back. The next thing you will do is probably write out an ad for the SOS free classifieds section to sell your machine at a knocked down price. Alternatively you could try the test, for comparison purposes, with a new machine. Don’t bother - it will sound dreadful too, all analogue tape recorders fail this test subjectively, and the narrower the track they record upon the worse the result will be. If you don’t have an oscillator then I’ll tell you what it sounds like. The original crystal clear tone becomes muffled and uneven, there is a hissing sound clearly audible behind it and there is a very obvious ‘popping’ noise at random intervals. The popping noise is, I believe, caused by very small dropouts which the ear misinterprets as sounds, rather than absences of sound. I have a very thick and expensive book on tape recording which fails to mention this ubiquitous phenomenon so any more plausible explanations will be welcome.

A problem with the recorded sound itself is something you can learn to accept and ignore, after all billions of recordings have been made on analogue equipment and sold to a generally satisfied public. It’s more difficult to accept operational problems because they affect your work again and again and you always have to find a way round them. One of the most serious problems is caused by the necessity to align the recorder. Aligning the recorder simply means that the heads and electronics are matched to a standard test tape produced in carefully controlled conditions, the reason being that if you want to play the tape on another machine ever, you will want it to sound exactly the same as it does on yours. In the professional world, line-up is vitally important as projects started in one studio will frequently pass through others along the way to the mix which will almost certainly be in the best mixing studio the producer can afford, within his budget. If the sound quality changes from one multitrack to another then problems, arguments even, are very likely to occur. In the personal studio, perhaps line-up isn’t quite so important since the multitrack tape may never pass out of the studio door. Nevertheless, the performance of the machine will drift in time and a tape recorded today may not sound the same in six month’s time unless you have the machine realigned (the provision of alignment controls is in itself a cause of misalignment).

Of course a digital machine needs to be aligned too, but the meaning of the word is subtly different. This is because the digital machine records numbers onto the tape. If these numbers can be read successfully then within the limits of the sampling rate and resolution, the sound will be perfect. It doesn’t matter if the form of the digit changes: 1234 has the value same as 1234, 1234 or 1234. Alignment in a digital machine involves setting the parameters of the control electronics for the rotary head so that the head follows the track accurately to give the best chance of retrieving all the numbers. This isn’t day to day line up, as would be done in a professional studio on an analogue multitrack. This is something a qualified service engineer would do on a regular, perhaps six monthly, basis. Probably the biggest alignment worry on an analogue machine is in ensuring that the heads are orientated exactly at 90 degrees to the direction of tape travel. If they are wrong, then terrible havoc is wreaked on the frequency response. On a rotary head digital recorder the azimuth, as it is called, of each record/playback element is fixed at manufacture, and small discrepancies would not affect performance anyway.

A post by David Mellor
Thursday January 01, 2004 ARCHIVE
David Mellor has been creating music and recording in professional and home studios for more than 30 years. This website is all about learning how to improve and have more fun with music and recording. If you enjoy creating music and recording it, then you're definitely in the right place :-)
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