KT88 quad, GEC NIB (branded Mullard) same date code !! V46 47 48 49

1.935,00

Highlights

    • King of the KT88 tubes
    • Old GEC UK production
    • NOS quad in original box
    • Best sonics

1 in stock

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Description

Rare Quad Mullard KT88 tubes; manufactured by GEC in Hammersmith, UK.

Detailed description

Here is a quad of new Mullard KT88 tubes. The tubes have been made in 1972 by GEC in Hammersmith, UK. I bought these valves years ago as spares for my Beard P100 power amplifier. But I never had to use them; these valves are said to last forever. (See my TT21 pair also!) The KT88 is a transmitting beam tetrode. It has three getters. The GEC KT88 is considered as the king of the KT88/6550 series. And of course delivers superior sonics compared to the Chinese and Russian new production KT88. 

The valves have excellent test values and are matched very well. Seems back in the 70’s they really understood how to make high(est) quality tubes. The valves are delivered in their original Mullard boxes.This quad is a real jewel, so please excuse the substantial price.

Note: my tubes are often not the cheapest. But it is very hard to find better tubes !

Sonics

The GEC (Mullard) KT88 is considered by many as the king of the KT88/6550 tubes; a better than any other! I refer to the many reviews on internet.

Test results

The measurement data below show that the tubes are very well matched. 

Valve 

V47

Ia (plate current):

Transconductance (Gm):

Gas test, Shorts test:

105  mA

9,9  mA/V

OK

> NOS

> NOS

 

Valve 

V50

Ia (plate current):

Transconductance (Gm):

Gas test, Shorts test:

107  mA

9,9  mA/V

OK

 > NOS

> NOS

 

Valve 

V48

Ia (plate current):

Transconductance (Gm):

Gas test, Shorts test:

102  mA

 9,5  mA/V

OK

>  NOS 

> NOS

 

Valve 

V49

 

Ia (plate current):

Transconductance (Gm):

Gas test, Shorts test:

94  mA

9,5  mA/V

OK

 > NOS

> NOS

 

Factory Specification for new unused tubes

  • The rated emission value for a new KT88 is:  57 mA.
  • The rated transconductance value for a new KT88 is:  8 mA/V. 

As specified in AVO Valve Data Manual 23rd edition 1981. 

Test conditions & equipment:

Mutual transconductance, plate current, gas and shorts test equipment: AVO Mk IV, AVO Valve Data Manual 23rd edition 1981, RFT stabilised mains, Utracer3+, Philips PE 4832, 2x Korad KA3005P programmable power supply, 2x Keithley 2700 and 2x Fluke 145. Test conditions: Ua (plate voltage) = 250 Volts, Us (screen voltage) = 250 Volts, Ug = -20 Volts and Uf = 6,3 V ± 3% (Factory conditions). 

Note: Please read our test page.

Summarized description

Tube type KT88
Quantity of Tubes One quad
Brand Mullard
Manufactured by GEC Hammersmith, UK
Date code 1972  code: 7217 Z
Plate Construction Welded grey plate
Getter Construction Three halo getters
Print Condition Excellent; see pictures
Box included Original Mullard box
Equivalent tubes:  6550A TT21
General test results  NOS
Please study photos carefully; what you see is what you get! Ask any questions before bidding. Thanks

Please read our test and shipping policy before buying !

Quad example