The earliest known concept of putting two or more identical
units inside a glass envelope goes back to the manufacture
of the first double-filament De Forest Audions. Over the years
several multiple or integrated valves were developed in the
USA and England. It was in Germany that the idea was developed
further. In the early twenties, just after WW I,
|Fig. 278 - The Loewe valve type
Germany was under the restriction of the Versailles Treaty.
Its bad economical situation had forced the government to
levy heavy taxes on many products including, of course, radio
receivers. The tax was determined generally by the number
of valves used in the radio. Dr. Sigmund Loewe,
|Fig. 277 - the electrical circuit inside
and outside the 3NF valve.
founder and owner of the company Loewe Radio AG of Berlin,
considered this peculiar situation and in 1926 working together
with Dr. Manfred von Ardenne, the pioneer in the researches
on the cathode ray tube, developed a thermionic device provided
with several elements inside a single glass envelop which
can be considered similar to a modern integrate circuit. Thus
in 1926, the company lauched in the German market the first
multipel valve. Later on, circa 1929, the Company developed
an interesting small radio receiver that used as its circuitry
a single multiple valve. Fig. 275
Considering the technology and materials available in the
early twenties, the manufcature of such valve was not an easy
task, requiring great proficiency in glass blowing as well
as skill in assembly. Fig 276
The best known Loewe multiple valves are the original types
3NF and 2HF. The 3NF (nieder frequenz) was used for low frequency
applications. I had a 6-pin bae with the following basic operation
conditions: filament 4V a 0.3 A, anode voltage 135 V. This
valve contained in a glass envelope three cascaded triode
amplifier valves, with their anode and grid resistors plus
the coupling capacitors. Fig 277
To avoid contamination of the vacuum in the envelope, the
capacitors and resistors were sealed individually in glass
capsules. Finally, the whole system was assembled in a complex
metal-glass structure on a special base. Fig 278
|Fig.275 - The O.E.-333 one-valve
radio and its plug-in coils.
Similar in size of its glass bulb, and using the same 6-pin
base, was the type 2HF (hoch frequenz), or a valve for high
frequency applications. It consisted of two of two tetrodes
arranged as a two stage RF amplifier with the following basic
operation conditions: filament 4 V at 0.17 A, anode voltage
In mid-'30s, the company product line comprised several types
of multiple valves for AC operation, such as the types WG
36 using a metal-shielded envelope.
Due its peculiar concept in its time, the Loewe multiple valve
was a step ahead as an innovative and reliable thermionic
device whose production was never attempted elsewhere. Through
his researche in circuitry, materials, and manufacturing process,
Dr. Loewe started a new trend in electronics - the miniaturization
of passive and active components - i.e., the birth of microelectronics
- and in this way he can be considered as a forerunner .
The multiple valve with 6 pins socket.
Fig.276 - the inner elements of the
3 NF valve.
Fig.277 a - X-ray view of the 3NF
valve. The three triodes, two horizontal and one vertical,
can be seen easily. Often they are not visible through
the bulb due to the getter flash.
- The American valve type 6N7. A twin triode made
circa 1930 that can be considered also a multiple
b- the multipe valve 3NF complete.