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Tube Amp Doctor - EL84-STR Premium - Power Tubes

Save $10.00
Original price $79.00
Current price $69.00

Harmonic middle tone and treble frequencies

The all new TAD-EL84STR brings together the best of both - the famous EL84-Cz and the EL84M. We opted for the thickest glass possible and the heaviest construction available, just like the Russian EL84M, and combined these features with the sonically most promising cathode plate options, in order to meet and exceed the tonal quality of the EL84-Cz. Finally, we added the gold grid wire in order to improve overall reliability. The sound can be described as very harmonic in the middle and treble frequencies, without adding too much power to the bass. The result is the best EL84 in current production.

No Compromise!

Very good in Epiphone Valve Junior (d= 22,5mm). Due to its diameter of 22.5mm, the TAD EL84-STR does not fit into older Marshall DSL401 and UK made VOX AC15 TBX amplifiers. The only tube which fits these amps is the EL84-EI. (ordering number: NN471)


Q: When does a power tube become a Premium Selected power tube?

A: All power tubes labeled Premium Selected have passed the following tests:

  • Plate Current (PC) and Amplification (TC)
  • Low Noise Test
  • Microphonic Test
  • Sonic Tests
  • Shock Tests
  • Listening Tests
  • Shorts & Leakage Tests


Premium RT-Matching of Power Tubes

Our Premium Matching is an exact matching of power tubes with identical Plate Current (PC) and Transconductance (TC).

TAD Premium Selected tubes are guaranteed for a period of 6 months (according to terms of warranties) for the quality criteria mentioned above.

RohS Compliant





  • Voltage (AC or DC) - 5.8V(min), 6.3V(nom.), 6.8V(max)
  • Current - ca 0.76A

Cathode: oxide-coated, unipotential

cathode-to-heater potential, max - +100V

Direct interelectrode capacitances, max*** -

  • Grid no.1 to cathode and grid no.3, and grid no.2 - base sleeve and heater <10.8pF
  • Plate to Cathode and grid no.3, grid no.2 - Base sleeve and heater <6.5pF / grid no.1 <0.5pF


  • Operating position - Any
  • Base - Noval, 9-pin
  • Dimensions - 77mm (height), 71mm (seated height), 22.5mm (diameter)
  • Cooling - Convection
  • Approximate net weight - 19g

AF Power Amplifier

Maximum Ratings

  • DC plate voltage - 420V
  • Grid no.2 DC (screen) voltage - 300V
  • Grid no.1 (control) voltage - -100V
  • DC Cathode current - 65mA
  • Plate dissipation - 12W
  • Grid no.2 DC (screen) dissipation - 2W

Typical Operation

AF Power Amplifier, Class A1 (single tube)

  • Plate Voltage - 250V
  • Grid 2 screen voltage - 250V
  • Grid 1 control voltage* - -4.8V
  • Peak AF Grid 1 control voltage - 14V
  • Zero signal plate current - 49.5mA
  • Maximum signal plate current - 80mA
  • Zero signal grid 2 screen current (avg) - 10.8mA
  • Transconductance (nominal) - ca 9.000 mS
  • Load resistance - 5200 Ohms
  • Output power at 9.5% distortion - 5.7W

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