6BQ5 / EL84 HAMMOND by Ei Gray Plates Halo Getter Matched Quad Tubes Made in YUGOSLAVIA

6BQ5 / EL84 HAMMOND by Ei – Gray Plates – Halo Getter – Matched Quad – Made in Yugoslavia AMPLITREX Matched Quad – VERY STRONG – Vintage Ei Production for HAMMOND Description: Matched quad of 6BQ5 / EL84 HAMMOND by Ei Niš, Made in Yugoslavia production, selected for hi-fi amplifiers, Hammond compatible, and musical applications requiring four consistent, stable, and vintage European character EL84s. The tubes were produced by Elektronska Industrija – Ei and branded for HAMMOND, the historic manufacturer of professional electronic organs. The construction features Gray Plates and Halo Getter, with the same manufacturing code KM4 ◉7I, a positive detail for production homogeneity and quad consistency. The silk-screening reads “Made in Germany”, but the manufacturing code KM4 ◉7I and construction characteristics identify the production as Ei Yugoslavia, consistent with typical European production of the era. The quad has been tested and selected using the Amplitrex AT-1000 Tube Tester as a Matched Quad, with a VERY STRONG result, very close values between the four tubes, stable emission, and 48h Burning Test passed. General aesthetic conditions are good. The HAMMOND silk-screening shows normal wear and tear over time, as visible in the photographs, while the internal structures are well preserved. Sonically, these EL84 Ei tubes offer a lively, musical, and well-articulated sound, with fast and controlled bass, natural and present mids, open highs, and good dynamic response. The matching of the quad promotes a stable soundstage and consistent presentation in compatible push-pull circuits. Suitable for EL84 / 6BQ5 push-pull amplifiers, vintage integrated amplifiers, Hammond compatible electronics, hi-fi restorations, and musical instrument amplifiers requiring a selected and reliable EL84 quad. An interesting vintage selection for those looking for an authentic, homogeneous, and musically convincing EL84 HAMMOND by Ei quad, tested and matched by Vacuum Tubes Treasures. Tested on AMPLITREX AT-1000 Tube tester: Voltage Test: Va = 250V, Vg2 = 250V, Vg1 = -7.3V Average 100% Gm = 11.3 ; Ia = 48 mA TEST RESULT: VERY STRONG Tube 1: Gm 10.90 ; Ia = 47 mA Tube 2: Gm 10.90 ; Ia = 47 mA Tube 3: Gm 10.87 ; Ia = 43 mA Tube 4: Gm 10.55 ; Ia = 42 mA Additional Tests Performed Burning Test: 48h – OK Microphony: Low. Tested and suitable for use in hi-fi and guitar amplifiers. Emission Quality: Excellent – very strong and stable emission, without fluctuations. Shorts and GAS: Absent. Conditions Conditions: Vintage Tubes - Tested and perfectly functional. Supplied in our custom box for optimal protection. Functionality: Perfectly operational. Aesthetic condition: Good – Lettering partially worn, but still legible. Tube body in good condition. See photos for details. Manufacturing Code: KM4 ◉7I → ◉ indicates the manufacturer, namely Elektronska industrija, YUGOSLAVIA. 7I → 7 indicates 1967, I indicates the month of September. Discover why our tubes are different →