EF804S Telefunken Germany <> bottom NOS (U5009505K=1965) very good printing

2.9ma

Gm=2100

(Special Quality 10,000+ Low Noise Pentode for microphones)

S = low noise

Tested on Amplitrex

Vplate=250V

Vscreen=140V

Vgrid=-2V

Good Ma = 2.5-3.5ma

Good Gm = 1800-2000

General Information

(Special Quality 10,000+ Low Noise Pentode for microphones)

HISTORY:
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In 1951 Telefunken started the 800 Series tube design and offered their improvement to the EF12 design; the EF804S is 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 which is a nearly microphonic-proof construction with a cathode coating. This tube was mainly used for the AEG/Telefunken Magnetophone production, but evolved into much of the professional studio equipment of the time. First the V72 was re-equipped with this state of the art Telefunken EF804S audio tube made in their Berlin and Ulm production. In 1967 in London, England, producer George Martin started to use EF804S equipped V72 pre amps for THE BEATLES ALBUM "SARGENT PEPPER" .