56

Small Signal Triode — UX5

RCA

Known Equivalents & Substitutes

CV611VT-5656A56S

Similar Tubes (Not Drop-In Compatible)

6P5G

Electrically identical but 6.3V heater and Octal base

6P5GT

Electrically identical but 6.3V heater and Octal base

Electrically identical but 6.3V/0.3A heater and Octal base — 56 uses 2.5V/1.0A and UX5

Electrical Specifications

Absolute Maximum

Anode Voltage (max)Plate Voltage (max)250V

Anode Dissipation (max)Plate Dissipation (max)1.3W

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

References