AEG Magnetophone K 4

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  • Manufacturer: AEG
  • Year of manufacture: 1938 - 1940

In 1938 the further developed device K4 was introduced. This device, which ran very stable due to the experience gained, was used in all large recording studios and broadcasting stations. Not only the better manageability compared to the wax plates offered advantages, but also the durability and storage of the sound recordings was now safely possible.

The tape running speed was 77 cm/s from this device on. This results in playing times of a little over 20 minutes for a tape length of approx. 1 km = 1,000 m. This is also a quantum leap compared to the wax plates used so far. The international standard later became 30"/sec. This is due to the takeover of war-looted equipment in the USA. The "conversion" to the standards in force there brought about this change: 60Hz instead of 50Hz mains frequency and inches instead of the metric system. Since the factories of the German manufacturers and also of AEG lay in ruins and many patents were lost, American manufacturers implemented the new data as standard internationally.

Technical data:

  • motors: 3
  • tubes: 6 pieces (2 x EF12, AH1, AF7, AL4, AZ1)
  • Tape width: 6,5 mm
  • Tape speed: 77 cm/s (standard value in European broadcast studios)
  • Frequency response: approx. 50 - 6500 Hz
  • Dynamic range: 38 dB
  • Playing time: approx. 20 minutes.


With audio sample on youtube:

In the radio museum you can find pictures: