Tube cross-reference
D3A alternatives, equivalents, and replacements
Review exact electrical variations and directional substitutions recorded for the D3A voltage pentode. Compare core specifications and verify every restriction before using a replacement.
Exact variations of D3A
These designations belong to the same electrical variation group. Their names may differ because of international standards, manufacturing tolerances, or materials, but they are recorded as electrically equivalent—not merely substitutes.
7721 Voltage Pentode
- Base
- 9EQ
- Socket
- B9A
- Base pins
- 9
- Sections
- 1
- Heater voltage
- 6.3 V
- Heater current
- 0.32 A
Verify before substituting
Matching a base or heater voltage is not enough to prove that two tubes are interchangeable. Check pin connections, heater current, maximum ratings, bias requirements, warm-up behavior, and the equipment manufacturer’s service documentation before making a substitution.
View the complete D3A specifications →