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EF37 — Small Signal Pentode, Octal | Tubeofile
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EF37
Small Signal Pentode — Octal
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Mullard
Data: High
High quality — base, heater, all universal parameters present, and ≥50% of desirable parameters filled in. Safe to use for design decisions.
↗ TDSL
↗ Radiomuseum
Known Equivalents & Substitutes
CV1404
Similar Tubes (Not Drop-In Compatible)
CV358
Military-graded variant
EF36
Predecessor — same basic design but without low-microphony construction
EF37A
Further improved version with even lower microphony and tighter specs
Electrical Specifications
Absolute Maximum
Anode Voltage (max)
Anode Voltage (max)
300
V
Screen Voltage (max)
Screen Voltage (max)
300
V
Anode Dissipation (max)
Anode Dissipation (max)
2.5
W
Typical Operating
Anode Voltage (typical)
Anode Voltage (typical)
250
V
Notes
Low-microphonic version of the EF36, intended for audio preamplifier use.
Octal base with top grid cap connection (IO/K8A).
Succeeded by the EF37A with additional improvements.
Pin Layout — Octal
1
2
3
4
5
6
7
8
1
No Connection
2
Heater
3
Anode (Plate)
4
Socket-Compatible Tubes
⚠ Not electrically compatible
EF36
References
https://tdsl.duncanamps.com/show.php?des=EF37
https://www.radiomuseum.org/tubes/?tube=EF37
Screen Voltage (typical)
Screen Voltage (typical)
100
V
Grid 1 Bias Voltage
Grid 1 Bias Voltage
-2
V
Anode Current
Anode Current
3.5
mA
Anode Resistance
Anode Resistance
1,000,000
Ω
Transconductance
Transconductance
1.6
mA/V
Heater
Heater Voltage
Heater Voltage
6.3
V
Heater Current
Heater Current
0.2
A
Screen Grid (g2)
5
Suppressor Grid (g3)
6
No Connection
7
Heater
8
Cathode
TC
Top Cap —
Control Grid (g1)