Their usage in the Next Generation V & U Modules.

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; western Germany alone made over 10 million 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; the post WWII version of the EF12 original used in the pre war V41.

Aside from a few problems with microphonics and "funkelrauschen" this tube enabled a modern self noise of -75dB, unheard in professional audio equipment.

In 1951 the historic German Telefunken Company started the 800 Series tube design and offered their follow up to the EF12 design; the EF804 an identical version of the EF40/EF86 but with a different pin layout that offered less cross talk from the 1950 standard AC heated filament.

They also used an improved cathode base material (made by the International Nickel Corporation in USA). This was a nearly microphonic-proof construction with a cathode coating that was also imported from the US General Electric Corporation.

This tube was mainly used for the AEG/Telefunken Magnetophone production, but found its way into much of the professional studio equipment of the time.

First the V72 was re-equipped with this state of the art EF804 audio tube made in their Berlin and Ulm production plants.

After Berlins production capacity was exhausted and only 30% of the EF804 tubes could be used for Encephalographs [in the medical world, another of it’s functions], so the plant in Ulm started a to develop an upgrade to this EF804 needed for medical equipment; the EF804S.

Some of the base material was changed, there was also a more intensive cleaning of the raw materials, and different wafer designs were implemented to push the limits of tube design.

On the 1st of May 1957 TFK started the first production run of 1500 tubes of these so-called EF804S, [the S stands for "Special"].

Two months after its introduction the IRT ordered all radiostations 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.

Over the years TFK made

800.000 EF804 in Ulm, and 337.000 in the Berlin plant

69.000 EF804S in Ulm, and 508.000 in the Berlin plant

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.

TFK was the only company that made the EF804S.

For a short period of time RFT [in East Germany] and Tungsram [in Hungary] made the EF804 but never could compete with the high production standard of the TFK tubes, so both RFT and Tungsram discontinued this in 1960.

In the mid-1980’s, TFK, the last Western manufacturer, stopped the production of Electron tubes.

From 1945 to the end of the production in the mid 80’s 670 million tubes were made in both of their West German production plants.

Today 25 years later one of the hardest tasks out there exists in trying to locate useable NOS replacement tubes for historic recording equipment, as none of the remaining tube manufacturers in the former East block can make a tube that is suitable for replacement.

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 EF804(s).

There is also the family of tubes that the EF804(s) belongs to; as mentioned before, despite the different pin layout, the EF804 is extremely similar to the EF40 and EF86.

TFK also made the EF86 and EF806, both of these tubes are identical to the EF804 and EF804s with only a variation in pin layout.

Phillips/Valvo tubes like the E80F, the Phillips/Mullard Z229 and the American made 5879 can also be used to replace EF804(s) 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 life time and sound of the historic V modules.

TFK claimed a min. life of 10.000 hours, but more likely 100.000 hours is the rule.