It became virtually extinct by the time Ronald Reagan ruled the free world, but did the relatively recent reintroduction of the 7591 vacuum tube manage to save our much loved vintage audio gear?
By: Ringo Bones
From the1966 Ampeg GS-12R electric guitar amp prized by Jazz guitarists for its clean Jazzy timbres to the famed Fisher and Hermon Hosmer Scott receivers from the Golden Age of Stereo, the reintroduction of the 7591 pentode output vacuum tube by Russian vacuum tube manufacturer Sovtek via their Electro Harmonix arm had made every vintage audio gear enthusiast and Jazz guitarist eternally grateful. The reintroduction even makes me wonder if the 1966 Ampeg GS-12 R guitar amp and the famed Fisher and H.H. Scott receivers were even popular in Soviet era Russia and the rest of the East-Block countries during the height of the Cold War.
Thanks to the reintroduction of the famed vacuum tube in the form of the Electro Harmonix 7591A EH, every Fisher 500-C and HH Scott 345 and related model receiver – or the 1966 Ampeg GS-12R guitar amp - using the tube can now be resurrected with ease – which was very a very daunting task back during the Reagan administration half of the 1980s where modern pentode type vacuum tube based circuits became extinct since they were slowly being phased out by the start of the 1970s due to the fact that every electronics engineer can more or less replace them with solid state parts - if sound quality degradation due to increased levels of overall negative feedback was overlooked.
Historically, the 7591 pentode vacuum tube was introduced in 1958 and registered with the EIA in 1960 after being developed and produced by Westinghouse’s receiving tube factory in Bath, New York. Given that Dr. Harvey C. Rentschler used to be the Director of Research for the Westinghouse Lamp Division, one could wonder if Dr. Rentschler was instrumental in the development of the 7591 vacuum tube. And by the way, the best NOS type of this tube was the famed 1962 Westinghouse 7591 which has a clearer sound than the new Electro Harmonix 7591.