Sophia Electric Classic 300B 2.5V Vacuum Tube Specification
| Filament voltage | *2.5V |
| Nominal filament current | 1.2A |
| Plate voltage | 300V |
| Grid voltage (AC filament) | **61V |
| Grid voltage (DC filament) | ***58V |
| Plate current | 60mA |
| Plate current | 62.5 mA |
| Grid to plate transconductance | 5700 ohms |
| Amplification factor | 3.85 |
| Grid current | 0.05 uA |
| Plate resistance | 700 ohms |
Limiting Operation conditions for safe operation-nor simultaneous ratings:
| Maximum plate voltage | 450 volts |
| Maximum plate dissipation | 40 watts |
| Maximum plate current of average tube for fixed grid bias | 70 ma |
| Maximum plate current for manually adjusted grid or self-biasing circuit | 100 ma |