AEG Magnetophon

What it is

The Magnetophon was the first practical tape recorder to use plastic-based magnetic tape. AEG, the Berlin electrical group, presented the K1 model at the Berlin radio exhibition in August 1935. Its tape came from the IG Farben works in Ludwigshafen, today BASF, which had delivered the first 50,000 metres to AEG in 1934. The K4 of 1938 was the first commercially successful version.

How it works

A thin plastic tape coated with fine iron oxide particles runs past a recording head, an electromagnet that magnetises the particles in step with the audio signal. On playback a second head reads the magnetic pattern back as a voltage. The breakthrough came in 1940, when Walter Weber and Hans Joachim von Braunmühl at the state broadcaster's laboratory added a high-frequency bias signal to the recording current. Noise and distortion fell so far that tape recordings could pass for live broadcasts.

Why it stands out

• Tape could be cut and spliced, so programmes could be edited for the first time without quality loss.
• Recording ran at one metre per second in early machines, giving fidelity no disc could match.
• German engineers made experimental stereo tape recordings in 1942 and 1943, more than a decade before stereo tape was sold.
• Its debut was nearly a disaster: a fire at the 1935 show destroyed the hall where the first machines stood.

Where you meet it

Indirectly, everywhere. The US Signal Corps engineer Jack Mullin shipped two Magnetophons and around fifty reels of tape home from the radio station at Bad Nauheim in 1945. His rebuilt machines recorded Bing Crosby's radio shows and inspired the Ampex Model 200A of 1948, the start of the American professional tape industry, of multitrack recording and later of videotape. Its tape side lives on at BASF's Ludwigshafen site, where the chemistry was first worked out.

Sources

• BASF: Chronology 1934
• Engel and Hammar: A selected history of magnetic recording
• IEEE Spectrum: The Magnetophon and the laugh track
• Wikipedia: Magnetophon