E443N

The Philips Miniwatt E443N is a directly heated audio-output pentode with a 4 V, approximately 1 A filament. Our historical sources place it in 1930. The German leaflet describes the same construction principles as B443/C443, but permits anode voltage up to 400 V and anode dissipation 12 W. This is a family comparison, not interchangeability without circuit changes; supply and bias must suit the E443N.

Stated applications include radio receivers and amplifiers driving multiple loudspeakers. A period curiosity is the leaflet’s example of two to twelve electromagnetic speakers or one or more electrodynamic speakers for restaurants and small halls up to 750 cubic metres. This is the manufacturer’s historical application description, not a modern system-sizing rule. For AC filament heating it recommends Philips transformer 4009 without a heater resistor; rectifiers 505 or 1071 are named for anode supply.

The documents’ characteristic sets remain separate. The trilingual table gives maximum anode 400 V, screen 200 V, normal anode current 30 mA, negative bias about 40 V, amplification factor 75, normal slope 1.9 mA/V, maximum slope 3.5 mA/V and normal internal resistance 40 kΩ. The German leaflet instead gives anode 300–400 V, screen 150–200 V, factor 60, slope 3 mA/V and internal resistance 20 kΩ. At screen 200 V it states normal current 30 mA and bias −37 V; required bias is −28 V at anode 300 V/screen 150 V, −37 V at 400/200 V.

The trilingual supplement gives two output results into 14 kΩ: 4 W with 14 V RMS grid input and 5.4 W with 20.2 V RMS. Those rows do not specify distortion; none is inferred from other valves. Curves include anode current against grid voltage for two supply ranges and anode characteristics at screen 200 V/filament 4 V. The anode family marks 12 W dissipation; an axis beyond 400 V does not increase permissible service voltage.

Supplementary limits include maximum cathode current 60 mA, service screen 200 V and screen dissipation 1.5 W. Average screen current is 5.4 mA, approximate range 3.5–7 mA. Zero-current anode voltage 650 V is separate from operating 400 V; no-load screen 400 V extends to 650 V with self-bias under the note. Grid-current onset is −2 V with 4 V AC filament, not cut-off voltage. Capacitances are anode-grid 0.9 pF, anode-cathode 8.3 pF and grid-cathode 11 pF.

The normal base is five-contact O40; the German leaflet identifies two filament contacts, control grid, screen grid and anode without numbers. Base width is 40 mm. Dimensions remain separate: trilingual table maximum overall length 110 mm/diameter 57 mm; German leaflet explicitly length excluding pins 110 mm/greatest diameter 58 mm. They are not merged into one height. Documentation: Philips Miniwatt E443N, trilingual table, supplement and two curve pages, four pages; German Philips Miniwatt E443N leaflet, pages 34–35, applications, base, characteristics and curve. No publication date is stated in the copies.