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Tube Amp Doctor - KT66 Premium - Power Tubes

Save $10.00
Original price $89.00
Current price $79.00

Out of the box old school tone

The TAD KT66 is our remake of the great British KT66 by MOV (MO Valve), GEC, Genalex and Gold Lion. This tube is THE REAL THING. It has a large curved glass envelope and a rounded brown base. It made the Marshall JTM45 Plexi amps famous in the 60's and the Quad Hi-Fi amps a legend.

Speaking of legends: SRV used the KT66 in his Fender Amps for his outrageous, gigantic guitar sound.



For a full bodied thick tone with larger headroom, smooth but detailed top end, single channel amps, dynamic playing, vintage British Rock and Roll as well as for the new modern vintage amps 2266 and 2466. It can also replace the 6L6GC and 5881 tubes.


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 1.27A

Cathode: oxide-coated, unipotential

cathode-to-heater potential, max - +150V

Direct interelectrode capacitances, max*** -

  • Grid no.1 to cathode and grid no.3, and grid no.2 - bass sleeve and heater <16pF
  • Plate to Cathode and grid no.3, grid no.2 - Bass sleeve and heater <11.5pF / grid no.1 <1.1pF


  • Operating position - Vertical
  • Base - octal, 8-pin
  • Dimensions - 129mm (height),116mm (seated height), 51mm (diameter)
  • Tube height (without pins): approx. 115mm.
  • Cooling - Convection
  • Approximate net weight - 72g

AF Power Amplifier

Maximum Ratings

  • DC plate voltage - 500V
  • Grid no.2 DC (screen) voltage - 400V
  • Grid no.1 (control) voltage - -300V
  • DC Cathode current - 100mA
  • Plate dissipation - 25W
  • Transconductance (nominal) - 8.500 mS
  • Grid no.2 DC (screen) dissipation - 3.5W

Typical Operation

AF Power Amplifier, Class A1 (single tube)

  • Plate Voltage - 250V
  • Grid 2 screen voltage - 250V
  • Grid 1 control voltage* - -15V
  • Plate current - 82mA
  • Grid 2 current - 5mA
  • Peak input grid 1 voltage - 15V
  • Load resistance - 2200 Ohms
  • Output power at 9% distortion - 7.25W



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