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As the vacuum tube gained in popularity and use, competition arose between U.S. manufacturers and European manufacturers to produce new tube types. Out of this competition arose the EL34, the 6L6, the 6550 and the KT88.

The original KT88 was produced by GEC in 1956 also labeled as IEC/Mullard, or Genelex Gold Lion. It was the European answer to the American 6550 tubes, and was specifically designed for audio amplification. The KT88 is also one of the largest vacuum tubes in its class.

JJ-Tesla KT88

Current production of the KT88 is limited to factories in China, Slovakia, and Russia. These include JJ-Tesla, Genalex Gold Lion reissues, as well as Sovtek, Electro-Harmonix and the newly available EAT tubes. Original production, unused (NOS) KT88 tubes in good condition are increasingly rare and expensive, sometimes costing $900 or more a pair. Historically these tubes have been more popular in hi-fi stereo equipment than in guitar amplifiers, since it provides high power and low distortion. Guitar amplifier owners will regularly use them to replace 6550 tubes, particularly if they want less distortion.

The KT88 fits a standard eight-pin octal socket, has can be used in similar applications as the 6L6 and EL34, since they have the same pinout.

From the original GEC description, points about the KT88:

1. The KT88 is a beam pentode with aligned grids for maximum efficiency.

2. 50 watts output is available from a pair connected in the ultra linear circuit with auto bias and an HT line voltage not exceeding 500.

3. 100 watts output is available from a pair connected in the ultra linear circuit with fixed bias and an HT voltage not exceeding 560.

4. 25 watts output is available from a pair triode connected with auto bias and an HT line voltage not exceeding 500.

5. The mutual conductance of the KT88 is 11mA/V

6. An all-glass ring seal replaces the conventional pinch seal giving increased strength, higher rating and reduced dimensions.

7. The valve is mounted on an international octal base and has a heater rating of 6.3 volts., 1.8 amps.

If you use KT88 tubes, tell us what you think. How do you use them? Which brand do you prefer?

We look forward to hearing what you have to say.

by Mary Klaebel

RCA created RCA Radiotron to make and sell radio tubes. Westinghouse manufactured the tubes in their Indianapolis plant, which was already producing more than 20,000 tubes daily. In 1931, fearing a monopoly, the U.S Government stepped in, so GE and Westinghouse broke ties with RCA in 1932.

Still, RCA became a primary tube manufacturer with their Radiotron brand radio tubes. The company’s innovations included the octal base metal tubes and the Nuvistor for television sets. Later, RCA even teamed with Tung-Sol to produce the hi-fi KT88/6550 vacuum tube.

With the Tung-Sol partnership, RCA so completely dominated the tube market that they were able to control the prices in the United States. Only the rise of solid state components in television and radio broke their hold on the market.

In addition to vacuum tubes, RCA began developing technology for television and computers. However, they were taken over by General Electric in 1986.

Today, the original RCA trademark is owned by a French company. Known as the “Meatball,” it is used by companies such as Sony BMG Entertainment and Audiovox.

Authentic RCA Radiotron tubes are still in circulation and in demand. But with no new RCA tubes being manufactured, the prices of certain new old stock tube types are quickly rising.

RCA’s beginnings wind through the creation and development of two other well-known companies - General Electric and Westinghouse Electric. It started with one man’s passion for electricity.

RCA Meatball Logo

Elihu Thomson was born in England in 1853. He grew up in Massachusetts. Even in high school, was aware of the possibilities electricity held for the future. As a student he wrote, “There is scarcely a day passing on which some new use for electricity is not discovered. It seems destined to become at some future time the means of obtaining light, heat, and mechanical force.”

Educated in science, Thomson became a professor at Philadelphia’s Central High School. In 1880, he and fellow science professor Edwin Houston established Thomson-Houston company, selling arc lamp systems. With their initial success they expanded into new markets, purchasing Sawyer & Man Electric Co. in 1886. They made incandescent lamps using the Sawyer-Man patents.

Over time, they built a leading electrical company of the nineteenth century. In 1889, after German physicist Heinrich Rudolf Hertz publicly released his initial work with electro-magnetic waves, Thomson addressed their use for signaling through fog or and solid bodies where light could not penetrate. At the time, Thomas Edison preferred direct current technology, and considered alternate current too dangerous. Thomson disagreed. It was his experiments with alternating current that led to it becoming the U.S. standard. In fact, Elihu Thomson’s system was lighting streets in Kansas City, Missouri six months before Thomas Edison opened his first power station in New York.

By 1890, Edison’s company, Edison General, and Thomson-Houston were two of the big three in the American lighting industry which also included Westinghouse Electric Co. In 1892, John Pierpont Morgan, who financed such enterprises as Federal Steel Company and Carnegie Steel Company, engineered a merger between the Edison interests and Thomson-Houston. He named the new company General Electric.

In his five-decade career, Elihu Thomson received 696 U.S. patents on numerous electrical inventions, including arc lights, generators, electric welding machines, and x-ray tubes. He even created a practical method for measuring the electrical consumption of homes and businesses, the wattmeter.

During World War II, in order to keep radio patents under American control, General Electric was asked to take the lead in organizing an American radio company. GE agreed, and the Radio Corporation of America was formed in October 1919. Though originally meant to merge the interests of both private corporations and the government for the development of wireless communication, RCA soon moved in a new direction. They entered the world of consumer electronics.

Within six years, RCA’s consumer radio sales were bringing in ten times the revenue “wireless technology” generated.

Westinghouse, an RCA manufacturer, became the first commercial broadcaster in 1920. Their station KDKA aired results of the Harding-Cox presidential election. RCA aired the world heavyweight boxing championship by the next summer. This ushered in a new era of technology in homes around the country.