SARATOV, Central Russia -- Eat your heart out, Yamaha. The vacuum tube production line here may not have changed much since the Reflektor factory opened in 1953, but that happens to be just what the world market wants.


The painstaking work of assembling tubes for amplifiers, stereos and other electrical devices is still done by hand at Reflektor, and the machinery dates back to the late Stalin era.


But this is not just another tale of a Russian dinosaur factory. Exports of Reflektor tubes have exploded in recent years, boosted by guitarists worldwide who prefer the vintage sound of tube amplifiers to the less soulful tones of solid-state electronics.


"In the end of the 1980s and the beginning of the 1990s, demand for the tubes began grow," said Vladimir Tupitsin, the factory's deputy director for marketing. Now "our tube division is more profitable than any other section of the factory."


To appreciate the allure of the tube amplifier, one has to conjure up electric guitar legends such as Jimi Hendrix, Carlos Santana and others who used tube -- or valve in British usage -- amplifiers to pioneer new distorted sounds in rock and roll in the 1960s. Yet as long as 30 years ago, music manufacturers began replacing the warm-sounding but temperamental tubes with transistors, which last longer and do not turn burning hot.


As the U.S. and the West scrapped their tube production, Russia kept on pumping out the glass-enclosed parts of the past. So when New York-based guitar effects designer Mike Matthews searched for a reliable source of new tubes, all trails led to Reflektor, a former defense electronics plant that won an Order of Lenin for overfilling the five-year plan of 1959-65.


Matthews started out by importing the Saratov-made tubes in the late 1980s through his New York-based company New Sensor, and eventually he secured an exclusive contract. Then, by 1991, he convinced Reflektor to build him guitar amplifiers as well.


"I started thinking if they make the vacuum tubes, why not make the whole amplifier, because all these factories are big vertical factories that have metal working shops, wind their own transformers, make their own PC boards," he said. "They're all self sufficient."


The result -- called the Sovtek MiG 50 -- has earned rave reviews in the guitar world.


"For the money, it's incredible," said David Grout, former guitarist of the Old Man Blues Band in Moscow "The sound is very satisfying; it's a good sort of medium-power club amp."


Reviewing the amp last year, Guitar Player Magazine wrote: "A toast to our Russian amp-building comrades: You guys kick butt."


For Matthews, the collaboration has expanded his initial $1,000 capital investment in 1988 to $5 million in annual sales, mostly based on tubes and amplifiers exported from Russia, he said in an interview from New York.


Yet as in so many cases of foreign dealings in Russia, the picture is not entirely rosy, officials on both sides say. Reflektor officials warn that they can no longer fulfill their three-year contract through 1996 to sell amplifiers at $90 a piece. They also want to raise tube prices.


"When we started it was profitable for us," said Tupitsin. "Now we must either raise prices or cut production."


Matthews, who wholesales the Sovtek amps for $189 in the U.S., responded that the factory's expenses are excessive because they refuse to cut costs by, for example, firing surplus workers.


"The problem is they have so much dead-weight overhead that they are keeping on the payroll," Matthews said. "Since our products are the only things working they try to fill overhead of the whole non-productive plant onto us."


Factory officials say their production of 2.5 million tubes a year -- about a quarter of which are exported -- accounts for little more than five percent of the total factory output.


Yet they do acknowledge that they have laid off few of their 7,000 workers earning $50 a month, and as a result, Reflektor had to close down many of its operations in May because of insufficient orders. Workers are only now receiving their April paychecks.


Matthews warns that if Reflektor cannot control its costs, their partnership with New Sensor could end.


He also says their amps are not as good as bigger name competitors such as Fender and Marshall, but have the crucial advantage of a price tag 50 percent lower than other amps of their class.


"If the costs go up, the competitive edge is lost and they'll lose the market," he said, "unless they can improve the quality, but they're too slow to react."