Heater-to-Cathode Voltage (max)Heater-Cathode Voltage (max)45V
Max Grid ResistorMax Grid Resistor1MΩ
Typical Operating
Notes
The 76 and 6P5GT are electrically identical to the 56 except for heater voltage (6.3V instead of 2.5V). The 56 is not a direct plug-in substitute for either.
If a grid-coupling resistor is used, its maximum value should not exceed 1.0 megohm.
The cathode should preferably be connected to a mid-tap on the heater supply winding or to a center-tapped 50 ohm resistor across the heater winding. Heater-to-cathode voltage must not exceed 45V.
Predecessor to the type 76; succeeded by 76, 6P5G, and 6P5M. Introduced in 1932.
The Sams Tube Substitution Handbook lists the 56 as a substitute for the type 27 and 27S (same base, similar characteristics but lower mu).
Pin Layout — UX5
1Heater
2Anode (Plate)
3Control Grid
4Cathode
5
Socket-Compatible Tubes ⚠ Not electrically compatible