CSPort writes: “With the addition of the balanced input and the use of polypropylene capacitors in the power supply, this non-feedback vacuum tube monaural power amplifier with a large triode 212E has achieved the clearer sound that CSPort pursues.” 

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 (1960-70s production) and Jinzhou Electronics’s 212E.

Two-stage configuration 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 input 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.

* The input impedance is 1.5 kΩ, and should be driven by equipment with an output impedance of 300 Ω or less.

Original regulated power supply

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.

Changes from 212PA

Additional Input Connections; Balanced inputs have been added to provide greater connectivity.

Capacitors in High Voltage Power Supply; Polypropylene capacitors have been used instead of oil capacitors to achieve a clearer sound.


  • Model 212PAM2-ST / 212PAM2-JH
  • Type Class-A Vacuum tube monaural power amplifier
  • Output Power 40 W (4 Ω, 8 Ω)
  • Frequency Response 20-40 kHz -3 dB/20 W
  • THD 1%/40 W 1 kHz, 0.2%/10 W 1kHz
  • NFB None
  • Signal to Noise Ratio 90 dB/10 W (8 Ω)
  • Input Sensitivity 1 V/40 W
  • Gain 25 dB (8 Ω)
  • Input Terminal Balanced x1, Unbalanced x1
  • Input Impedance 1.5 kΩ
  • Volume Adjustment None
  • Dumping Factor 5 or more
  • Power Supply AC100/120/200/240 V, 50/60 Hz
  • Power Consumption 400 W
  • Dimensions 188W×385H×563D mm *
  • Weight 24.5 kg
  • Finishing
  • Anodic oxide coating, Rosewood plates  
  • Accessories AC cords
  • Warranty Period 5 years(Excluding consumables)
* Knobs and terminals are not included.
The input impedance of this unit is 1.5 kΩ. 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.
  • Product appearance and specifications are subject to change without notice.