KT88 quad, GEC NOS Original GEC boxes V22 51 52 60

Description

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

Detailed description

Here is a quad of very strong and matched quad GEC KT88 tubes. All four tubes have been produced the 70’s by GEC in Hammersmith, UK. All four tubes are assumed to be unused. The flash doesn’t show deterioration. They have been tested in my Beard P100 and sound fantastic. Note that one tube shows some some coloration on the label; this is caused during these test in the Bard.

Most people have heard of the famous GEC KT88, which has become known as the best sounding KT88 ever made. It is known for a smooth but extended treble, warm but accurate mid-range, and thunderous bottom end. It’s fame has caused this tube to become nearly impossible to find.

This is the original vintage GEC KT88 (NOT a Russian or Chinese) reissue)! The vintage GEC KT88 is a legend that was produced in the period from the end of the fifties till he end of the seventies. The tube is a so-called kindles tetrode (KT) and was the British response to the famous USA Tung Sol 6550. It was designed to be the much stronger stablemate of their KT66, which was used in the Quad II amplifiers (and many other) to very good effect.

The tube is a powerhouse; amplifiers that were designed for the vintage KT88 (like e.g. Mcintosh Mc75 and Mc275, Beard P100 and others) often will blow the modern reissues. And of course delivers superior sonics compared to the Chinese and Russian production KT88. Till today no modern tube construction can replace the original GEC KT88. They lasts almost forever; even when the getter flash has disappeared many KT88 tubes still perform strong.

This quad of KT88 valves has incredible nice test values and are matched very well. Seems back in the golden tube era they really understood how to make high(est) quality tubes.

The valves are delivered their original GEC boxes.This quad is a real jewel also, so please excuse the firm price.

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

Sonics

The vintage GEC KT88 creates an open sound image with a natural midrange, silky trebles and a solid bass. The GEC KT88 is considered by many as the king of the KT88/6550 tubes; better than any other! I refer to the many reviews on internet.

Test results

The measurement data below show that the tubes are excellent matched. 

Valve  V22

Ia (plate current): Transconductance (Gm): Gas test, Shorts test:

72  mA 8,5  mA/V OK

> NOS > NOS

Valve  V51

Ia (plate current): Transconductance (Gm): Gas test, Shorts test:

73  mA 8,3  mA/V OK

> NOS > NOS

Valve  V52

Ia (plate current): Transconductance (Gm): Gas test, Shorts test:

72  mA  8,3  mA/V OK

>  NOS  > NOS

Valve  V60

Ia (plate current): Transconductance (Gm): Gas test, Shorts test:

75  mA 8.4  mA/V OK

> NOS > NOS

Factory AVO Specification for new unused KT88 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 (Factory conditions). 

Note: Please read our test page.

Summarized description