Analog Audio Tape Machines

Open reel analog tape recorders are quite fascinating for a number of reasons. A lot more interesting than you would think at first sight!

I've owned a ReVox A77 since 1986, and in August 2007, I finally got around to restoring it to something like the way it should be. This page goes in to the gory details. Some of it is a little naieve - I now know a little bit more about the characteristics of analog tape - but it might be useful if you happen to own a Dolby B version of the A77.

In October 2007, I was lucky enough to win a Studer A812 on E-Bay for a suprisingly small amount of money. This is an example of the last generation of analog tape recorders for studio use and is a very complex machine with a network of microprocessors controlling all its mechanical and audio functions. I hope to make a page soon with measurements of its performance and related things. I think it would be fair to describe that performance as exemplary.

Please note that I don't believe "analog is better than digital" or anything equally silly. In theory, digital audio can be to all intents and purposes "perfect" - (with some clear consequences ... for example, all CD players should sound exactly the same, whether they cost £100 or £10,000). To what extent this potential perfection is actually realized, I am not sure!

In any case, analog tape is capable of very high quality results - subjectively, if not objectively!. It is worth remembering that almost every piece of music recorded between the early 1950's and the mid 1980's was recorded on analog tape. Quite a lot was recorded on it after that date, too. A very small amount still is - usually for the sake of specific "effects" such as so-called "tape compression".

Apart from how they sound, the best machines are also magnificent pieces of engineering, and are well worth preserving.

Here are a few reasons why I find these machines particularly interesting:

  • The objective, measured, performance of analog magnetic tape recorders is pretty unimpressive. Usually, if a piece of equipment has poor measured performance, it doesn't sound very good. This doesn't seem to be true for tape. If you concentrate on doing so, you will hear defects. The overall effect, however, tends to be pleasing. The (many) deficiencies must be of a kind the ear doesn't much care about. What you might call: "euphonic". This has implications for audio equipment in general. More on this ...
  • The basic characteristics of the recording medium are a pretty awful basis for high quality audio recording. How this fundamental problem was (step by step) overcome is an interesting story.
  • Perhaps the most important single step to high quality recording was the introduction of HF AC bias. This was independently discovered at least three times before it was finally put to good use! It may be hard to believe, but the details of how HF AC bias linearizes the transfer characteristic of magnetic tape is still something of a mystery! It may be obsolete, but it is still (arguably) not fully understood ... There is more (far too much, probably) on this here ...

I've gained a great deal of satisfaction and enjoyment from maintaining and using these machines. Looking around the Internet, it would seem I am not alone.

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