The svetlana from original svetlana Russian factory brown heavy base - quiet, noteworthy amazing tube. Nice swirling harmonic content. The construction of the tube is outstanding and I feel it contributes to the overall performance.
RCA 6146 Brown Base Vintage Vacuum Tube NEW with box. Tested NOS on a professionally calibrated TV7U tube tester
FOR SALE,STRONG MATCHED PAIR OF GE USN-5Y3WGTB 6087 TUBES. DATE CODES, 60-43 (1960 WEEK 43) AND 61-52 (1961 WEEK 52). THESE TUBES HAVE BLACK PLATES AND SQUARE GETTERS. TUBE #1 TESTED 59/59. TUBE #2 TESTED 59/59.
Fine pair of Sylvania 5692 brown base tubes, labeled for Westinghouse, with original boxes. Gm matched to about 9% difference on the Amplitrex AT1000. Shiny black plates, micanol bases, multiple support rods, thick glass, triple micas, and double getters all make for a bulletproof tube.