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The Stradi PX25 is electrically compatible with the original PX25 model, but its tube cage conforms to Eb tubes because it is relatively free from the space charge accumulation problem.

The PX25 tube is one of the best-known European direct-heated triodes and, as the name suggests, has a maximum plate dissipation factor of 25 Watt (later increased to 30 Watt).
It was used a lot in many places because it can produce relatively high output among direct heated triodes made in Europe.

Its amplification factor is 9.5, which is when a voltage of 400V or more is supplied to the plate, this was to reduce the difficulties of designing a voltage amplifier circuit caused by a high bias voltage.
Due to this, however, the internal resistance of the vacuum tube inevitably increased, which led to the unique characteristics of the PX25, such as non-irritating, soft and comfortable sound.

The original PX25 tube has very wide space between the plates.
Due to this, space charges are accumulated between the grid and the plate, causing distortion.
To solve this problem, an additional grid was inserted between the grid and the plate in some cases.

The electrical characteristics of the Stradi PX25 tube are compatible with the previous PX25 models but the tube cage is based on the Eb tube.
The Eb vacuum tube is relatively free from the space charge accumulation problem because the plate and grid are relatively close.

Available in matched pairs, quad sets, and singles.

  • Availability In Stock
  • Lead Time 3 ~ 14 days
  • Price$440.00

  • Ladder type Frame Grid
  • Material of minimizing filament end-loss
  • Anti-microphonic structure
  • Electrophoresis filament coating
  • Dual Getters
  • Eco-friendly paper packaging


  • Filament Voltage : 4 Volt (AC or DC)
  • Tolerance on filament voltage : +-2.5 %
  • Filament Current : 2.0 Ampere


  • Maximum Anode Voltage : 500V
  • Maximum Anode Dissipation : 30Watt
  • Maximum Anode Current : 100mA


  • Anode Supply Voltage : 400V
  • Grid Voltage : -31V
  • Anode Current : 62mA
  • Transconductance : 8000 µmhos
  • Anode Resistance : 1188 Ω
  • Amplification factor : 9.5
  • Load Resistance : 3200 Ω
  • Power Output : 6Watt