Tube cross-reference
KT33 alternatives, equivalents, and replacements
Review exact electrical variations and directional substitutions recorded for the KT33 power - tetrode (not beam). Compare core specifications and verify every restriction before using a replacement.
Replacement tubes for KT33
The following tubes are recorded as possible replacements for KT33. This direction does not establish that KT33 can replace them.
Power - Pentode Single (NOT beam) (under 10W)
The database records 25A6 as a possible replacement forKT33.
No special restrictions are recorded for this substitution.
| Specification | Original tube | Replacement |
|---|---|---|
| Tube type | Power - Tetrode (NOT beam) | Power - Pentode Single (NOT beam) (under 10W) |
| Construction | Tetrode | Pentode |
| Base | Not recorded | 7S |
| Socket | IO | IO |
| Base pins | 8 | 7 |
| Sections | 1 | 1 |
| Heater voltage | 25 V | 25 V |
| Heater current | 0.3 A | 0.3 A |
Where KT33 can be used as the replacement
In these recorded relationships, KT33 is the replacement tube. The listed original tubes are not automatically suitable as replacements for KT33.
Power - Pentode Single (NOT beam) (under 10W)
The database records KT33 as a possible replacement for25A6.
No special restrictions are recorded for this substitution.
| Specification | KT33 replacement | Original tube |
|---|---|---|
| Tube type | Power - Tetrode (NOT beam) | Power - Pentode Single (NOT beam) (under 10W) |
| Construction | Tetrode | Pentode |
| Base | Not recorded | 7S |
| Socket | IO | IO |
| Base pins | 8 | 7 |
| Sections | 1 | 1 |
| Heater voltage | 25 V | 25 V |
| Heater current | 0.3 A | 0.3 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 KT33 specifications →