AEG Magnetophone K 7

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  • Manufacturer: AEG
  • Year of manufacture: 1944

The K7 unit is a pre-production unit. This device combines two essential steps of development:

The tape is properly premagnetized:

The two developers Walter Weber and Hans-Joachim von Braunmüh discovered high frequency premagnetization by accident. This considerably reduces tape noise and also improves the distortion factor. This now made recordings of very good quality for the time possible.

This device had a special stereo-capable sound head, a two-track sound head.

With the help of two microphones, stereo recordings were now possible for the first time. Microphones of the Neumann brand were used for this purpose.

The quality of these recordings, when broadcast on the radio (these devices were studio devices), was indistinguishable from live broadcasts. There are very few surviving recordings, below is a link to a recording on YouTube.

Technical data:

  • Voltage: 220 V
  • Motors: 3
  • Tubes: ?
  • Bandwidth: 6,5 mm
  • Tape speed: 77 cm/s
  • Frequency response: unknown
  • Dynamic: unknown


Image at


And a youtube link: