TUBE: 7581A (datasheet titled 7581-A)
FICHIER SOURCE: sheets/135/7/7581A.pdf
FABRICANT: General Electric (GE Electronics, Receiving Tube Department, Owensboro, Kentucky)
ANNÉE: 1963 (4-63; curves FEBRUARY 10, 1959 & FEBRUARY 27, 1963)
TYPE: Beam Pentode (beam power tube / beam tetrode)

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GE 7581-A — BEAM PENTODE
For AF Power-Amplifier Applications
"The 7581-A is a beam-power pentode primarily designed for use in audio-frequency power-amplifier applications. The 7581-A is unilaterally interchangeable with the 7581 and the 6L6-GC."

ELECTRICAL:
Cathode - Coated Unipotential
Heater Voltage, AC or DC ... 6.3 ± 0.6 Volts
Heater Current ... 0.9 Amperes
Direct Interelectrode Capacitances (approx.):
  Grid-Number 1 to Plate (g1 to p) ... 0.6 pf
  Input: g1 to (h+k+b.p.+g2) ... 10 pf
  Output: p to (h+k+b.p.+g2) ... 6.5 pf

MECHANICAL:
Operating Position - Any
Envelope - T-12, Glass
Base - B6-148, Short Medium-Shell Octal 6-Pin Micanol
Outline Drawing - EIA 12-15
Maximum Diameter ... 1-9/16 in
Maximum Over-all Length ... 4-1/4 in
Maximum Seated Height ... 3-11/16 in

MAXIMUM RATINGS (Design-Maximum Values):
                              Pentode Conn / Triode Conn
Plate Voltage ... 500 / 450 Volts
Screen Voltage ... 450 / --- Volts
Plate Dissipation ... 35 / 35 Watts
Screen Dissipation ... 5.0 / --- Watts
Heater-Cathode Voltage: Heater Positive w.r.t. Cathode ... 200 / 200 Volts; Heater Negative w.r.t. Cathode ... 200 / 200 Volts
Grid-Number 1 Circuit Resistance: Fixed Bias 0.1 / 0.1 MΩ; Cathode Bias 0.5 / 0.5 MΩ

TERMINAL CONNECTIONS (BASING DIAGRAM EIA 7AC):
Pin 2 - Heater
Pin 3 - Plate
Pin 4 - Grid Number 2 (Screen)
Pin 5 - Grid Number 1
Pin 7 - Heater
Pin 8 - Cathode and Beam Plates

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CHARACTERISTICS AND TYPICAL OPERATION — AVERAGE CHARACTERISTICS:
Plate Voltage ... 70 / 250 Volts
Screen Voltage ... 300 / 250 Volts
Grid-Number 1 Voltage ... 0(Δ) / -14 Volts
Plate Resistance, approx. ... --- / 22500 Ohms
Transconductance ... --- / 6000 Micromhos
Plate Current ... 210 / 72 mA
Screen Current ... 25 / 5.0 mA

CLASS A1 AMPLIFIER, TRIODE CONNECTION:
Plate Voltage ... 250 V; Grid-No.1 Voltage ... -20 V; Peak AF Grid-No.1 ... 20 V
Amplification Factor ... 8; Plate Resistance ... 1700 Ohms; Transconductance ... 4700 µmhos
Zero-Sig Plate I ... 40 mA; Max-Sig Plate I ... 44 mA; Load ... 5000 Ohms; THD ... 5%; Power ... 1.4 W

CLASS A1 AMPLIFIER, PENTODE CONNECTION:
Plate Voltage ... 250 / 300 / 350 Volts
Screen Voltage ... 250 / 200 / 250 Volts
Grid-Number 1 Voltage ... -14 / -12.5 / -18 Volts
Peak AF Grid-No.1 ... 14 / 12.5 / 18 Volts
Plate Resistance ... 22500 / 35000 / 33000 Ohms
Transconductance ... 6000 / 5300 / 5200 Micromhos
Zero-Sig Plate I ... 72 / 48 / 54 mA
Max-Sig Plate I ... 79 / 55 / 66 mA
Zero-Sig Screen I ... 5.0 / 2.5 / 2.5 mA
Max-Sig Screen I ... 7.3 / 4.7 / 7.0 mA
Load Resistance ... 2500 / 4500 / 4200 Ohms
THD ... 10 / 11 / 15 %
Max-Sig Power ... 6.5 / 6.5 / 10.8 W

PUSH-PULL CLASS A1 (2 tubes):
Plate 250/270; Screen 250/270; Grid-No.1 -16/-17.5; Peak G-G 32/35
Zero-Sig Plate I 120/134; Max-Sig Plate I 140/155; Zero-Sig Screen I 10/11; Max-Sig Screen I 16/17
Eff Load P-P 5000/5000; THD 2/2%; Power 14.5/17.5 W

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PUSH-PULL CLASS AB1 (2 tubes):
Plate 360/360/450; Screen 270/270/400; Grid-No.1 -22.5/-22.5/-37; Peak G-G 45/45/70
Zero-Sig Plate I 88/88/116; Max-Sig Plate I 132/140/210; Zero-Sig Screen I 5.0/5.0/5.6; Max-Sig Screen I 15/11/22
Eff Load P-P 6600/3800/5600; THD 2/2/1.8%; Power 26.5/18/55 W

PUSH-PULL CLASS AB2 (2 tubes):
Plate 360/360; Screen 225/270; Grid-No.1 -18/-22.5; Peak G-G 52/72
Zero-Sig Plate I 78/88; Max-Sig Plate I 142/205; Zero-Sig Screen I 3.5/5.0; Max-Sig Screen I 11/16
Eff Load P-P 6000/3800; THD 2/2%; Power 31/47 W
Notes: (‡) With screen connected to plate. (¶) Max screen 500V in PP where screen tapped on plate winding. (Δ) Short interval (2s max).

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[courbes seules — average plate characteristics triode connection (screen tied to plate); average plate characteristics Ec2=250V]

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[courbes seules — average plate characteristics Ec2=250V; average transfer characteristics Eb=250V]

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[courbes seules — average transfer characteristics Eb=250V (screen); average plate characteristics Ec1=0V (Ec2 family to 400V)]

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[courbes seules — average screen characteristics Ec1=0V; average plate characteristics Ec2=400V]

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[courbes seules — average plate characteristics Ec2=400V; average transfer characteristics Eb=400V]

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[courbes seules — average transfer characteristics Eb=400V; operation characteristics Eb=Ec2=250V Ec1=-14V Esig=9.9V rms]

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[courbes seules — operation characteristics 2 tubes PP Class AB1, Eb=450V Ec2=400V Ec1=-37V RL=5600Ω]