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Fastback Telefunken Stereo V72 Preamps


Posted on February 18th, by Mitch in Blog. No Comments

Development of the V72

The North West German Radio (NWDR), working in cooperation with the Institute of Broadcast Technology (IRT) of Hamburg, developed a completely new equipment standard for the German radio network. This led to the development of the historic V72 module. The V72 was developed by the NWDR under the technical supervision of Professor Nestler between 1949 and 1952 as a microphone and main studio amplifier. Nestler had previously been the head of R&D for the AEG/Telefunken Electro Acoustic Lab (ELA).

 

The V72 was modeled on the V41 and the circuits are almost identical with the exception of the gain control section. The V72 also utilized modern advancements like Noval glass tubes and a smaller housing, the “Danner” cassette module. The first 100 units were built at the NWDR Zentraltechnik. Serial numbers 101 to 300 were built by Maihak. These units were built with a set of EF40 tubes, the post-war glass version of the EF12. In later models, this tube was changed out for the sonically superior EF804 and EF804S.

 

The V72 was a self contained amplifier with a fixed gain level of 34 dB. It was originally used as a microphone amplifier used in conjunction with a Neumann W75k high pass filter and as a buffering amplifier to make up for loss of the passive fader like the Danner MR66/88 and Eckmiller W86 EQs. By 1955 it was the standard preamplifier in German radio stations. With the introduction of the V76, it was replaced as an input module and relegated to use as a buffering amplifier. In 1963 it was decommissioned by the IRT and replaced by the V72t transistor version.

 

An estimated 25000 V72 modules were built for the German Radio Network alone. The early versions were built by Maihak and Telefunken/AEG. In 1954 Siemens and TAB became sub contractors to make the historic V72. Aside from the German radio stations, the V72 was used by most of the European Recording Companies like EMI, Decca/Telefunken, etc. Siemens designed the V72s to accommodate the specific needs of these recording studios. These units featured a fixed gain of 40 dB and lower input impedance.

 

Telefunken used the V72s as standard preamplifiers for their broadcast division. In 1960 AEG-Telefunken was the world’s largest manufacturer of broadcast systems and sold these units to radio stations in South America, Africa and the Middle East, where most of them are still in use today. In 1966 the production of the V72 stopped at Telefunken. Siemens stopped their production in 1964 but built the V72b version up until to 1966. TAB was the only company that built the V72a up into the 70s.

 

The Historic V72, Today

Today the V72 is still in demand, but most units are now at least 35 years old and need to be rebuilt or refurbished. The electrolytic caps of the power supply are dried out and need to be replaced. The silk-wire of the unit falls apart to the touch and in most cases this winds up shorting out the input and output transformers.

 

The units also suffered when given phantom power. If a standard on/off phantom power supply was used, it would send an arc of electricity up to 2000V across the input transformer that would slowly burn the transformer’s insulation, thus destroying it. Most historic V72 units purchased second hand need to be completely refurbished (new caps, wiring, transformers and tubes) in order to operate at their designed specification.  ~ This article is provided courtesy of, tab-funkenwerk.com

 

The Stereo pair of V72 at Fastback Studios do not have filters and phantom power so ribbon microphones can be used by with. Our studio pair of V72’s have been modded by the EMI Studios engineering team in the mid 1960’s from the fixed gain level of 34 dB to 40 dB.

V72

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