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Tube Tinker — Electron Tube Database

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A2521 alternatives, equivalents, and replacements

Review exact electrical variations and directional substitutions recorded for the A2521 voltage - triode (single high frequency). Compare core specifications and verify every restriction before using a replacement.

Exact variations of A2521

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.

  • 6CR4

    Voltage - Triode (single high frequency)

    Base
    Not recorded
    Socket
    Not recorded
    Base pins
    9
    Sections
    1
    Heater voltage
    6.3 V
    Heater current
    0.37 A
  • CV2453

    Voltage - Triode (single high frequency)

    Base
    Not recorded
    Socket
    Not recorded
    Base pins
    Not recorded
    Sections
    1
    Heater voltage
    6.3 V
    Heater current
    0.37 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 A2521 specifications →