DC11

The DC11 is a directly heated battery triode, presented by Telefunken as an audio driver. The sheet documents transformer or choke coupling, a defined audio-chain role rather than a generic power output stage. The file includes two technical pages and an index dating them to 1941; this is not treated as the tube’s introduction year.

Nominal filament rating is 1.2 V, 25 mA, distinct from a secondary input figure of 20 mA. The note specifies design for one dry cell, allowing voltage to fall from usual initial values to 0.9 V in that service. With another source, such as an accumulator or mains supply, heater-voltage tolerance is ±15%. The table’s 1.4 V limit refers to the same note and must be read with source conditions. All sheet voltages reference the negative filament end, not a separate cathode.

Two audio points are given: plate 120 V, grid −4.5 V, plate current 2.5 mA; or plate 90 V, grid −3 V, current 2 mA. Both have transconductance 0.9 mA/V and internal resistance 17 kΩ. Durchgriff, the plate penetration parameter, is 6.5%, not distortion. The document gives no circuit output power or distortion at these points, so none is added.

Limits distinguish cold plate voltage 200 V from operating plate voltage 150 V; maximum plate dissipation 0.4 W, cathode current 4 mA, grid-leak resistance 3 MΩ. Grid-current onset is −0.5 V at current no greater than 0.3 µA, distinct from plate-current cutoff. Page two shows transfer curves at 120 and 90 V and plate characteristics for various grid voltages, including the 0.4 W dissipation hyperbola. Axis values do not replace operating limits.

The base diagram, identified in the archive as German Y8A, distinguishes plate, grid, positive and negative filament ends and metal envelope connected to the negative end. Contacts are not numbered in the drawing; numeric assignments are not invented from another base. Dimensions shown are body diameter 36 mm, base diameter 43 mm, height above the contact seating plane 43.5 mm, with a separate 15.5 mm lower projection. These dimensions are not marked maximum; weight explicitly is maximum 50 g. Documentation: Telefunken, DC11, Triode – Treiberröhre, sheets 011241-a and 011241-b, 1941; digital-file index dated March 4, 2000.