Historic Telefunken Tubes
Historic Telefunken Tubes
The first tubes used in the Historic V72
At the beginning
of the 1950’s when most of the U/V modules were developed, electron tubes were the industry standard in the western
world. In fact, West Germany produced over 10 million tubes a year. Despite this common practice and familiarity,
the choice of tube components for the V72 were very carefully investigated. The first 300 V72 units made at Malotki
and Zentraltechnik of the NWDR radio station used the Philips/Valvo developed EF40. Developed in the 1940's the
EF 40 was a glass version of the EF12 which was originally used in the pre-war V41. With the exception of
a few problems with microphonics and "funkelrauschen", this tube achieved a modern measurement of -75 dB of self
noise, which was unheard of in professional audio equipment at that time.
Telefunken AG's 800 Series and the introduction of the EF804
In 1951, AEG/Telefunken started the 800 Series tube design
and offered their follow up to the EF12 design. The EF804 was an identical version of the EF40/EF86 but with a different
pin layout that provided less cross talk than the 1950 standard AC heated filament. The tube also featured an improved cathode base material (made by the International Nickel
Corporation in USA) that used a cathode coating also imported from the US from General Electric. The construction of
this cathode made the tube virtually microphonic-proof. While this tube was chiefly designed for use in the AEG/Telefunken Magnetophone, it found its way into much of
the professional studio equipment of the time. The first
historic V72's to be re-equipped with this state of the art EF804 audio tube were made in the Berlin and Ulm production
plants.
Development of the EF804s
After the Berlin factory's production capacity was exhausted
and only 30% of the EF804 tubes could be used for Encephalographs, the plant in Ulm started to develop an upgrade to this
EF804 needed for the medical equipment industry; the EF804S. Some of the base material was changed, there was a more intensive cleaning of the raw materials and different wafer
designs were implemented to push the limits of tube design. On May 1, 1957 AEG Telefunken GmbH started the first production run of 1500 tubes of these so-called
EF804S (the S stood for "Spezial" or special). Two
months after its introduction, the IRT ordered all radio stations to retube their V72’s and V76’s with the EF804S
in order to bring down the self noise of the V72 to -88dB and -120dB for the V76. This was despite the fact that the cost
of the new tube was twice the amount of the standard version.
Two out of the first 1000 handmade "0"
Series EF804s, please note the new construction design
Production Numbers
Over the years, Telefunken (in its various corporate forms) produced:
EF804: 800,000 in Ulm, 337,000 in Berlin
EF804s: 69,000 in Ulm, 508,000 in Berlin
Most of the EF804 tubes were used by companies
like Grundig and AEG for tapemachines, where-as the EF804S was mainly used for specialty electronics where the best possible
S/N ratio with low microphonics was needed. The historic Telefunken company was the only company that
made the EF804S. For a short period of time RFT (East Germany) and Tungsram (Hungary) manufactured
a version of the EF804 but neither company's factories could compete with the high production standard of the Telefunken
made tubes. As a result, both RFT and Tungsram discontinued their production of the EF804 in 1960.
The last production run at the end of the 70s
a couple "Silver Specials" where made, please note the last two digits on the date code indicate the revision #,
over the years Telefunken changed the design 8 times.
Telefunken AG Ends Production
In the mid-1980’s, Telefunken AG, the last Western
manufacturer of vacuum tubes, ceased production. From
1945 to the end of production, Telefunken AG had produced over 670 million tubes between both of their West German production
plants. Today, over 20 years later, one of the
hardest tasks is to locate useable NOS replacement tubes for historic recording equipment as none of the remaining tube manufacturers
in the former East block can meet the high standards created and achieved by the historic Telefunken company.
The identical electron system of the EF804 and
EF804S was used for TFK EF806 and EF806S a very low noise/long live version of the EF86.
Our Commitment to NOS Tubes
When we started our V series project in the mid 1990’s,
we located and bought most of these tubes to insure a safe supply of EF804S tubes. There is also the family of tubes to which the EF804S belongs. As mentioned above, despite
the different pin layout, the EF804 is extremely similar to the EF40 and EF86. Telefunken also made the EF806, which is identical to the EF804 and EF804S with only a variation
in its pin layout. Phillips/Valvo tubes like the E80F,
the Phillips/Mullard Z229 and the American made 5879 can also be used to replace an EF804S if the pin layout is changed.
Today we use for all our next generation V and U series modules
the genuine TFK, AEG and Phillips/ Valvo tubes, the only way to insure the same longevity and sound of the historic V
modules. Telefunken claimed that their tubes would
last through a minimum of 10,000 hours, but with proper care, 100,000 hours is fully achievable.
Aside the EF806s (shown the
pic above the paragraph) we use Philips made E80F, here shown labeled with as AEG and TFK EF844s (a special version of the
EF804s that was only made for R&S)for our V71DI, V72S and V76S
My very special "thank you" to Rudolf for all his help and information
about the inside of a vacuum tube.
