product description:
A closely matched pair (2 tubes) of military-grade GE 5654W vacuum tubes. The mil-spec GE 5654W was originally designed as a premium-grade substitute for 6AK5 and EF95 vacuum tubes. The "W" designation refers to ruggedized, military grade, tubes; better quality control and internal design changes to enhance reliability. These mint-condition vintage tubes, which have a 1988 manufacture date, have never been used. This great sounding vintage tube has found new life as a replacement for 6J1, 6AK5 and EF95 tubes used in headphone and other audio amplifiers and is often used by amplifier designer s and tube roller s looking for improved sound quality. At Riverstone Audio, we personally inspect, test and match these vacuum tubes. Effective October 2016, all 5654 vacuum tubes sold by Riverstone Audio are precision-matched using a state-of-the-art Amplitrex AT1000 digital tester. For each matched pair, mutual conductance and plate current readings differ by less than 4% between tubes (for many headphone amplifier circuits, similar plate current can improve channel balance). All tubes selected for our matched-tube pairs test at NOS (new old stock) levels of 5000 micro-mho or higher (tested using fixed-bias at a plate and screen voltage of 120 V and a grid voltage of 2.0 V). Other quality checks include shorts/leakage, gas, noise and a life test. The life test involves reducing the tube filament voltage by 10% and re-measuring mutual conductance. Tubes that pass the life test generally provide longer operating life. Boxes are labeled with measured plate current and mutual conductance. Tubes that show even the slightest abnormality in the quality checks or life test are rejected (we reject over 40% of the NOS 5654W tubes we test!). Only the best tubes are selected by Riverstone Audio for use as matched pairs. ***PLEASE NOTE*** Vacuum tubes tested and matched by Riverstone Audio will bear the Riverstone name, logo and quality control label on the boxes.
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