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Tube Amp Doctor - KT88-STR Premium - Power Tubes

Save $30.00
Original price $189.00
Current price $159.00

Wonderful tone and great appearance suitable for High-End audio and bass guitar amps

The latest version of our TAD KT88-STR is built in the style of the early British MOV KT88. It has the same big and heavy glass envelope and beautifully polished metal base. Its wonderful tone and great appearance make this tube the most attractive choice for high-end audio applications and powerful bass guitar amps.

It offers a vivid and three-dimensional tone, pleasingly warm, detailed and with subtle highs. A very musical reaction, with great sound and finest details in mids and top-end; a linear and harmonious overall response with a very natural tone, make the TAD KT88-STR our favorite tube in the KT88 and 6550A class.


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 1.6A


Cathode-to-heater potential, max - +250V

Direct interelectrode capacitances, max *** -

  • Grid no.1 to cathode and grid no.3, grid no.2 - base sleeve and heater <17pF
  • Plate to cathode and grid no.3, grid no.2 - base and sleeve heater <12pf grid="" no="" 1="" to="" plate="" 3pf="" li="">


  • Operating postion - vertical
  • Dimensions - 114mm(height), 103mm(seated height), 52mm(diameter)
  • Cooling - convection
  • Approximate net weight - 90g

AF Power Amplifier

Maximum Ratings

  • DC plate voltage - 800V
  • Grid no.2 DC(screen) voltage - 600V
  • Grid no.1(control) voltage - -300V
  • DC Cathode current - 230mA
  • Plate dissipation - 42W
  • Grid no.2 DC(screen) dissipation - 8W
  • Plate + grid 2 dissipation - 46W
  • Bulb temperature(surface hottest point) - 250 degrees celcius

Typical Operation

AF power amplifier, Class A1 (single tube)

  • Plate voltage - 400V
  • Grid 2 screen voltage - 225V
  • Grid 1 control voltage* - -16.5V
  • Peak AF grid 1 control voltage - 16.5V
  • Zero signal plate current - 87mA
  • Maximum signal plate current - 105mA
  • .
  • Zero signal grid 2 screen current (avg) - 4mA
  • Transconductance (nominal) - 9,000 mS
  • Load resistance - 6000 Ohms
  • Output power at 5% distortion - 19W

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