KT88 vs KT66
KT88 versus KT66 — two tetrodes compared.
KT88 vs KT66: which one to choose?
The KT88 and KT66 share a family but trade gain for headroom: KT88 has the higher amplification factor (μ ≈ 8), making it the typical choice for high-gain preamp stages. KT66 runs lower μ (—) and is the standard cathode follower / phase-splitter / line-stage triode. They share the same envelope and base — wire them in the same socket and only the operating point changes.
Side-by-side specifications
| Spec | KT88 | KT66 |
|---|---|---|
| Full name | KT88 | KT66 |
| Type | Tetrode | Tetrode |
| Primary use | Power (PP) | Power (PP/SE) |
| Era | 1956 | 1937 |
| Heating | indirect | indirect |
| Heater voltage | 6.3 V | 6.3 V |
| Heater current | 1.6 A | 1.3 A |
| Amplification factor (μ) | 8 | — |
| Transconductance (gm) | 11.5 mA/V | 7 mA/V |
| Plate resistance (rp) | 12 kΩ | 23 kΩ |
| Max plate voltage | 800 V | 550 V |
| Max plate dissipation | 42 W | 30 W |
| Base | octal | octal |
| Manufacturer | GEC | GEC·Marconi |
| Rarity | Sought-after | Sought-after |
Sonic character
Need an interactive deep dive?
The Amperatubes comparator visualises loadlines for both tubes side-by-side, simulates the SPICE response, and lets you adjust the operating point in real time.
Open KT88 vs KT66 in the interactive comparator →