[78-L] 1950 Telefunken 10" records with up to 9 minutes per side

[Benno Häupl]

. 
Some of you readers may be interested in seeing such record. 

As from 1942, German Telefunken engineer Eduard Rhein developed a recording 
process that automatically cut the next groove closer to the previous one when 
there were softer sounds. 
Depending on amplitudes and frequencies, it was possible to have up to 9 minutes 
of music on a regular 25cm (10") record that was played with a normal pick up 
and needle, and at the usual speed of 78 revolutions per minute.  

To do this, Rhein used a 56-tube computer that calculated how much the groove 
could be approached for the next revolution. In practice there was an extra 
playback head at the tape recorder which controlled which intensity in amplitude and 
what frequencies would be coming up at 1/78th of a minute later, i.e. 0.7692 seconds).

This processus was called 'Füllschrift' It was patented in 1948 and introduced in 1950.  
The name Füllschrift suggested that the 'Schrift' (writing or recording) was 'filled' 
or 'full' (of sound?). 

At about the same time Deutsche Grammophon did a similar invention, except 
that they brought the grooves closer together at soft spots by a 6 tube device.  
When there was a fortissimo, then the next groove was kept further apart for 
an extra revolution for safety reasons to keep the walls strong enough. Therefore 
Deutsche Grammophon's gain was not as impressive as Herr Rhein's. 

If you want to see such a Telefunken 'Füllschrift' 78 in its special promotion sleeve, 
here's such a rarity on sale at ebay Germany: 

http://cgi.ebay.com/ws/eBayISAPI.dll?ViewItem&item=180636544327  

Benno 

.