TUBE: EL33
SOURCE FILE: sheets/129/e/EL33.pdf
MANUFACTURER: Mullard (ISSUE 2; code EL33 858)
YEAR: n/a (Issue 2)
TYPE (per PDF): OUTPUT PENTODE (High-sensitivity output pentode for A.C. mains equipment)
PAGES: 2 (both data-bearing)

===== PAGE 1 =====
OUTPUT PENTODE — EL33 (Mullard)
HEATER: Vh = 6.3 V ; Ih = 0.9 A
CAPACITANCE: c(a-g1) = 1.0 µµF (pF)

OPERATING CONDITIONS AS CLASS "A" AMPLIFIER:
  Va = 250 V ; Vg2 = 250 V ; Ia = 36 mA ; Vg1 = -6.0 V ; Ig2 = 4.0 mA
  gm = 9.0 mA/V ; ra = 50 kΩ ; µ(g1-g2) = 23
  Pout = 4.0 W ; Ra = 7.0 kΩ
  Vin(rms) = 4.2 V ; Vin(rms)(Pout=50mW) = 0.33 V
  Dtot = 10 % ; Rk = 150 Ω

OPERATING CONDITIONS FOR TWO VALVES IN PUSH-PULL:
  Va = 250 V ; Vg2 = 250 V
  Ia(0) = 2x24 mA ; Ia max = 2x28.5 mA
  Ig2(0) = 2x2.8 mA ; Ig2 max = 2x4.6 mA
  Rk = 140 Ω ; Ra-a = 10 kΩ
  Pout = 8.2 W ; Vin(rms) = 6.7 V ; Dtot = 3.1 %

OPERATING CONDITIONS AS TRIODE (g2 connected to a):
  Va = 250 V ; Ia = 20 mA ; Vg = -8.5 V
  gm = 6.5 mA/V ; µ = 20 ; ra = 3.0 kΩ
  Rk = 425 Ω ; Ra = 7.0 kΩ
  Pout = 1.1 W ; Dtot = 5.0 % ; Vin(rms) = 5.9 V ; Vin(rms)(Pout=50mW) = 1.1 V

FOOTER: ISSUE 2 — Mullard — EL33 858-1

===== PAGE 2 =====
EL33 — OUTPUT PENTODE (Mullard)
LIMITING VALUES:
  Va(b) max = 550 V
  Va max = 250 V
  pa max = 9.0 W
  Vg2(b) max = 550 V
  Vg2 max = 275 V
  pg2 max (zero sig.) = 1.2 W
  pg2 max (max. sig.) = 2.5 W
  Ik max = 55 mA
  Vg1 max (Ig1=0.3µA) = -1.3 V
  Rg1-k max = 1.0 MΩ
  Vh-k max = 50 V
  Rh-k max = 5.0 kΩ

ELECTRODE ARRANGEMENT / OCTAL BASE (pin circle):
  a (top, separate cap-style top pin shown as 'a'); g2 g1 at top of circle; g3 and a near; h h on sides; k bottom.
  Diagram labels: a=top; g3, g2, g1 grids; k, h, h at base. OCTAL BASE.
  Dimensions: 46 mm max dia; 126 mm max height.

FOOTER: ISSUE 2 — Mullard — EL33 858-2

NOTE: Mullard Va max = 250 V, Vg2 max = 275 V, Vh-k max = 50 V. Confirms PENTODE (g1,g2,g3 = 3 grids). Triode-connected mode listed (g2 to a) but tube is structurally a pentode.