Despite Smith's hints at using other media than wire, it remains the media of choice (together with steel tape) until the 1930's, when AEG and BASF develop a paper-coated tape. The AEG "Magnetofon K1" is revealed to the public in the 1935, recording on paper tape at a speed of 100 cm/s. In America, steel wire and tape are still the preferred recording medium.
At this point, magnetic recording history becomes clouded with the political situation in Germany and the rest of the world at this time. Studying American texts reveals that most advances were made in America, whereas German history tends to show a different picture. Regardless of which is correct, one of the most colorful accounts from this time is the invention of AC bias; in Germany in 1941 a fault in a tape recorder amplifier causes the output stage to oscillate, and the resulting recording then shows a surprising clarity, hitherto unheard of. Thus the high-frequency AC bias is born (superimposing a high-frequency signal, in the order of several tens of kHz, onto the recording signal).
After the war, tape gains popularity. AEG introduces their first amateur machine in 1951, the KL 15. Grundig starts manufacturing tape recorders a couple of years later, with the 300 and 500 series. Philips releases its first successful amateur machine, the EL3510, in 1955. Already in 1949, a company called Maihak introduces a professional portable recorder, using a clockwork motor and battery operated tube amplfier. Small speed regulated DC motors were unheard of at this time; although the ultra-miniaturized Minifon Mi51 wire recorder appears as early as 1951, using a subminiature electric motor, it still uses a mechanical centrifugal governor for speed regulation.
In 1953, the Maihak "Reportofon MMK3" becomes the machine of choice for professional use. The machine has a camera synchronization option, and becomes popular in the film industry as well. With a playing time (per wind-up) of 7.5 minutes, and only supporting small 3" reels, it is not designed for long periods of operation.
So far, home users have had to resort to mains-operated equipment. This is in stark contrast to the development of radio several decades earlier, where battery equipment was the first to evolve in the non-professional world, for the simple reason that most households did not have mains power in the early 20th century! Apart from the fact that mains electricity has become widespread in the 1950's, another reason for the development of mains operated tape recorders is the relative simplicity of obtaining a constant speed tape drive by utilizing an AC motor synchronized to the mains frequency.
Around the middle of the 1950's, I would guess 1954, the company releases the "Butoba", short for Burger Tonbandgerät ("Burger Tape Recorder"). It is a simple machine for amateur use, yet offering two tape speeds (9.5 cm/s and the non-standard 6.3 cm/s) and a reel size of 5". The amplfier uses battery tubes, operated from a standard 100V radio anode battery and a 1.5V filament battery. Although it can't be considered cheap, an attempt at keeping the price down is done by omitting almost everything but the bare essentials; there is no fast forward for instance, and rewind must be performed manually.
Further development leads to the addition of a socket for external power supply (for operation from the mains), and a running time counter, showing the amount of time before the machine must be wound up again. The result is the "Export". Although intended as an amateur machine, and lacking professional features such as a battery level monitor or camera synchronization, the Butoba tends to get used by professionals nonetheless because of its favourable price compared to the Maihak or Nagra. An example of this is the Danish commercial radio station Radio Mercur in the late 1950's and early 1960's.
In 1958 the Burger company is split into two companies: Burger Industriewerk KG (Burger Industrial Works) manufacturing mechanical components, and Schwarzwälder Uhrwerkefabrik Burger KG (Burger Black Forest Clockworks Factory), the latter continuing to manufacture clocks and the Butoba recorder. Both companies still exist today, the former as BIW Burger Industriewerk GmbH & Co. KG, and the latter as SBS-Feintechnik GmbH & Co. KG. Both specialize in the manufacture of precision mechanics.
Around this time it seems that Burger changes the naming convention of their machines, from giving them names (like the "Export") to giving them type codes, (like TPR2). Transistors start to replace tubes in home equipment, and a transistorized version of the machine is released, the TS6.
The MT4 is released around 1959, and it is mechanically a radical design change from earlier machines, with a 6V motor for play and record, using an electromechanical centrifugal regulator in order to keep the speed constant (i.e. a switch is mounted on the motor shaft, controlling the motor electrical current via a transistor, and being actuated by a small small weight affected by centrifugal force). A separate motor is used for fast forward and rewind. A few minor developments lead to the MT5, released around 1960. Despite having a high price tag, the machine becomes popular, and is used for such varying tasks as recording native peoples chants in far corners of the world (for example, see the Dogrib tea dance page), or as a luxery sound system in motor cars.
Meanwhile, also released around 1959, the
is an updated TS6, still using
clockwork mechanics, but with almost the same electronics as the MT4/MT5
(the difference being that the TS61 has smaller transformers in the
signal path, compromising bass response). Having a running time of 22 minutes
at 3 3/4 ips (40 minutes at 7 1/2 ips) together with large "D" cells
operating only the amplifier, this machine boasts a long playing time
on a single set of batteries. It is the last Butoba
clockwork tape recorder to be produced.
At the start of the 1960's, competition begins to stiffen, as other established manfacturers launch into the portable market. Uher and Telefunken for instance market small, reliable recorders for amateur use, and it is difficult for a small manufacturer such as Burger to keep up. A final attempt is made in 1962, when the MT7 (right) is released. It is a small battery operated recorder with single 6V motor and 3" reel size, and looks similar in style to the battery operated cassette recorders which will appear a couple of years later. True to its heritage, the recorder still uses a DM71 valve as its recording indicator.
Looking back, it would seem that the Burger company simply did not have the muscle to keep going in the expanding tape recorder market. Although having an initial edge with the clockwork drive, other manufacturers soon caught up once electric motors became the norm. The Butoba electronics were always on the simple side; on the one hand, resulting in a clean and clear sound, on the other hand, lack of features made for cumbersome use. For instance, the tone control is active not only during playback but also during record; obviously it is easy to forget to reset the tone control to its neutral position, and get a recording which is improperly equalized. Similarily, equalization is only designed for the higher speed with no switching, the lower speed suffering accordingly. Also, the Butobas seem to have a record/play equalization of their own, yielding good results if the tapes were played back on the same machine, but making the interchange of high fidelity recordings awkward. Another example is the recording bias frequency which is as low as 30 kHz on all machines; this was common for machines of the mid-1950's, but generally recorders of the 1960's tended to use a 50 kHz or higher bias frequency, in order to minimize the risk of interference with the audio signal.
Back to my Vintage magnetic recording page.