300B vs 845
300B versus 845 — two triodes compared.
300B vs 845: which one to choose?
Moving from the 300B to the 845 is one of the classic upgrade paths in tube audio. The 845 delivers more power (~100 W vs ~40 W), more bass authority, and tighter control — at the cost of a different sonic signature and a substantially higher running cost (current consumption, transformer requirements, NOS prices). Most builds cannot socket-swap; the chassis layout, output transformer, and power supply must be re-engineered.
Side-by-side specifications
| Spec | 300B | 845 |
|---|---|---|
| Full name | 300B | 845 |
| Type | Triode | Triode |
| Primary use | Power (SET) | Transmitting (SET) |
| Era | 1938 | 1931 |
| Heating | direct | direct |
| Heater voltage | 5 V | 10 V |
| Heater current | 1.2 A | 3.25 A |
| Amplification factor (μ) | 3.85 | 5.3 |
| Transconductance (gm) | 5.3 mA/V | 3.1 mA/V |
| Plate resistance (rp) | 700 Ω | 1.7 kΩ |
| Max plate voltage | 450 V | 1250 V |
| Max plate dissipation | 40 W | 100 W |
| Base | ux4 | ux4 |
| Manufacturer | Western Electric | RCA |
| Rarity | Legendary | Moderate |
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 300B vs 845 in the interactive comparator →