Refinements in Phonographic TechnologyUp until around 1953, Neumann built disk-cutting lathes for phonograph records with a constant groove pitch. Between 1953 and 1955, Neumann developed a method of varying the groove pitch depending on the recorded amplitude. To this end, an additional playback head was mounted on the tape deck. This additional playback head determined the groove amplitude to be recorded approximately one half-rotation of the turntable in advance and fed this value to the cutting lathe as a control signal via a corresponding drive amplifier. Of course, this also required a separately variable pitch drive. For the first time, this made it possible to extend the playing time of an LP phonograph record to approx. thirty minutes.
So far the records had been monophonic disks made using lateral recording. In 1956, Neumann debuted its first stereo disk-cutting lathe, the ZS 90/45, which supported both lateral and vertical recording. The lathe was set up to cut the two stereo channels into the two flanks of the groove at a 45° angle. Over the years, other disk cutting lathes were developed, the quality of which improved continually. These were all electrodynamical feedback cutterheads. This model series continued with the SX 45, SX 68, SX 74 and finally the SX 84.
Many companies made a name for themselves with their products on the disk cutting market. These included, for example, Ortofon, Westrex, Scully, Fairchild, Dauphine, and others. By the end of the fifties, Neumann was the only company left that could deliver complete tape-to-disk transfer equipment. Neumann saw this position as a serious obligation to continue refining phonographic technology. This was reflected in the refinement of the disk cutting lathes and improvement of the cutting procedure.
One interesting phenomenon in this connection is the tracing distortion that results from the difference in geometric shape between the tool used to cut the grooves and the playback stylus. The cutting stylus is shaped like a spade, while the playback stylus is spherical. During playback, this results in tracing distortion, which mainly contains the 2nd harmonic. In 1968, Neumann built the Tracing Simulator that solved this problem.
In the early seventies, Neumann successfully developed, in conjunction with TELDEC, a mechanically recorded video record that was played back via a pressure pickup. The experience gained in this connection led to another significant improvement in the process of cutting phonograph records. In the beginning, phonograph records were cut in bee's wax and for years thereafter in a phonographic foil coated with nitro-cellulose lacquer. Neumann introduced the DMM technology, in which the phonographic foil was replaced by copper foil, resulting in Direct Metal Mastering, DMM. This resulted in substantially improved pulse fidelity of the recorded signal, which represented another significant improvement in the sound quality of phonographic records.
Disc cutting head SX 74
Complete tape-to-disk transfer equipment
DMM-disc cutting equipment