Mini disk

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The mini-disk , or micro-disk , is a mechanical , but digital storage medium developed by the company Teldec ( Telefunken - Decca Schallplatten GmbH) in the early 1980s . It is considered to be one of the last technologies competing with compact disks (CD).

The aim of the development was a system that, despite modern digital data coding , could be produced comparatively inexpensively and at the time with mature technology due to its similarity to the conventional record (LP). By manufacturing the discs from vinyl , neither new production facilities (e.g. presses ) nor completely new technology for reading out the data were necessary, as in the case of optical "scanning" of a CD, for example. The then Telefunken director Rolf Schiering spoke in 1981 of ninety percent less material and forty percent less wage costs compared to conventional LP.

The mini-disk was never launched. At the time of the presentation, Telefunken was already struggling with economic difficulties. While the compact disk developers Philips and Sony were able to convince many well-known companies to participate in their development and produce their own devices and data carriers, Telefunken did not find a partner for the mini disk. It also remains doubtful whether consumers would have accepted the technology. In the early 1980s, vinyl records were regarded as crackling, impractical and in need of care relics; the hi-fi market thirsted for easy-to-use, interference-free technology. The CD met these expectations with its non-contact, optical scanning and an information layer encased in plastic. The mini-disk would have had a hard time with mechanical scanning in comparison.

Technology of the MD system

The diameter of the mini disc is only 135 mm (5.3 inches) with a playing time of 2 × 60 min (when writing on both sides). The micro-disk, which is identical to the mini-disk except for its size, has a diameter of 75 mm (2.9 inches) and offers 2 × 10 min stereo recording time.

The MD system works with mechanical piezoelectric scanning via a needle, but digitally stores the information in its grooves. This means that no mechanical interference noise is read out during the scan . With 14- bit coding and a system for error correction , which theoretically results in a signal-to-noise ratio of 85  dB , the MD system is quite competitive with the CD.

Just like its competitors, it allows access to any point on the target at any time, with which, for example, pause or repeat functions can be implemented. In contrast to records, the information is stored in the grooves via a purely vertical modulation of their height. As with the LP, the grooves start at the edge of the plate and end in the middle.

Both formats are always enclosed in a cassette that protects against damage or dirt and does not need to be removed for playback. With the exception of the playback process, it is always completely closed.


Individual evidence

  1. Article about the mini disk and its competing technologies. In: Die Zeit , 35th edition, 1981