The XLR input was added, and the power supply was changed to polypropylene capacitors. This non-feedback tube monaural power amplifier with large triode 212E embodies the clear sound that CSPort pursues.

Monaural Power Amplifier 212PAM2


Large triode 212E

The 212E is a transmitter and modulation tube with a plate loss of 275 W, developed by Western Electric in the 1910s. Class-A single tube amplifier has difficulty driving a low efficiency speaker, but this unit has a plate voltage of 1,400 V and an output of 40 W. The damping factor of 5 or more is achieved by reducing the output power, so it can drive the low frequency range reliably.

・Two models are available: STC's 4212E and Jinzhou Electronics's 212E.


Two-stage with C3g

Equipped with the ultra-reliable C3g, developed by Deutsche Telekom for telephone repeaters. The thin grid lines and large distance between electrodes enable high linearity amplification. Using only two tubes of amplification with the 212E, harmonics and mixed-modulation distortions are suppressed though no-feedback.


High fidelity transformer

The input transformer makes up for the lack of gain in the two-stage amplification. It is received by a high linearity transformer with a high permeability super permalloy core and does not add anything extra.

・Please drive with a equipment with an output impedance of 300 Ω or less.


Unique power supply

Rectifiers and contacts used in general power supplies are sources of noise, and the quality of the power supply is linked to sound quality. We utilize a dual regulated power supply with a switching regulator in the first stage and an after-analog regulator in the second stage, which has been optimized for audio based on many years of knowledge in power supply development. Stabilizes the high-voltage 1,400V in the end stage.



212PAM2-ST / 212PAM2-JH


Class-A Vacuum tube monaural power amplifier

Output Power

40 W (4 Ω, 8 Ω)

Frequency Response

20-40k Hz -3 dB/20 W


1%/40 W 1k Hz, 0.2%/10 W 1k Hz



Signal to Noise Ratio

90 dB/10 W (8 Ω)

Input Sensitivity

1 V/40 W


25 dB (8 Ω)

Input Terminal

Balanced x1, Unbalanced x1

Input Impedance

1.5k Ω

Volume Adjustment


Dumping Factor

5 or more

Power Supply

AC100/120/200/240 V, 50/60 Hz

Power Consumption

400 W


188W×370H×563D mm


24.5 kg


Anodised aluminium, Rosewood plates  


AC cords

Warranty Period

5 years

  • The input impedance of this unit is 1.5k Ω. Please use a equipment with an output impedance of 300 Ω or less.
  • Two models are available: STC 4212E (model: 212PAM2-ST) and Jinzhou Electronics 212E (model: 212PAM2-JH).
  • The 4212E made by STC is a rare item, so please contact us for availability.
  • Do not touch the vacuum tube as it is hot and may cause burns.
  • Vacuum tubes are treated as consumables and are not covered by warranty.
  • Dimensions do not include legs, knobs, or terminals.
  • The descriptions are current as of March 31, 2023.
  • The appearance and specifications are subject to change without notice.
  • Actual colors may differ from those in the photographs due to shooting, lighting, etc.

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