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Closely Matched Pair of General Electric (GE) JAN 5654W Vacuum Tubes.  6AK5, 6AK5W, EF95, 6J1, 6J1P Replacement

Only the best tubes are selected by Riverstone Audio for use as matched pairs. The mil-spec General Electric (GE) JAN 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. This great sounding vintage tube has found new life as a premium replacement for 6J1, 6J1P, 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 pair these vacuum tubes for both plate current and mutual conductance.  As a final step, prior to shipping, all tube sets are also subjected to an audio test in a preamplifier.
Effective October 2016, all 5654 vacuum tubes sold by Riverstone Audio are precision-matched using state-of-the-art Amplitrex AT1000 digital testers.  In early 2017 we purchased an additional 16,000 GE 5654 vacuum tubes.  With this purchase, we currently have an inventory of over 75,000 NOS GE JAN 5654W vacuum tubes - all still in their original factory-sealed cartons and with the manufacture dates that we have found provide the best quality 5654 tubes for high fidelity audio applications.  With an inventory this large, we are able to select the best tubes for our use in our matched pairs and quads.  Our tubes have gone through several stages of inspection, including detailed electrical parameter and life testing and an audio sound check by our engineers. Vacuum tubes that show even the slightest abnormality in the quality checks are rejected by us for audio use.  Fewer than 50% of NOS 5654W tubes that we test meet our benchmark for high fidelity audio use and are ultimately selected for use in our matched tube sets. Although many of the tubes we reject meet acceptable NOS ranges for mutual conductance, plate current and grid current, they simply do not meet our standards for use in high fidelity audio applications.  Our reject rate we find for Russian made 6J1P tubes is even higher - we reject more than 65% of the 6J1P tubes we test.  Yes - many of the 5654 and 6J1P tubes we reject will still work; however, in our opinion, they are just not good enough to bring out the best sound quality in audio pre-amps, amplifiers and 6AK5/5654 based microphones. 
A few comments on tube testing and matching...for audio-tube matching, plate current is by far the most important parameter.  We match these premium grade tube pairs for BOTH plate current and mutual conductance.  Matching for both parameters provides better balance over a wider range of operating voltages.  For a given matched pair, mutual conductance readings differ by less than 200 micro-mho, with plate current differing by less than 0.2 mA (for many headphone amplifier circuits, having similar plate current is important for channel balance). All tubes selected for matched pairs are guaranteed to test at NOS (new old stock) levels with mutual conductance of 5000 micro-mho or higher and plate current above 7.0 mA (tubes are tested under fixed-bias, at a plate and screen voltage of 120 V and grid voltage of 2.0 V). Boxes are labeled with measured plate current and mutual conductance. These mint-condition NOS/NIB vintage tubes have matching date codes and, prior to our parameter testing, have never been used.