NOS 12ax7 CV492 Of all the 12AX7 tubes we have tested here at Tejas Tubes, these amazing CV492 smooth plate tubes made in pre-war Yugoslovia have tested with some of the highest umos levels we have seen! These were also used as original equipment in the Audio Research SP-6/8. Here is what one of our customers have said about these powerful tubes: " These tubes kick butt! A huge upgrade for the Behringer 1953 microphone pre-amp!" Brian Puglisi If you are an audiofile or musician, you owe it to yourself to pick up a couple of these NOS tubes! Tejas Tubes has one of the largest known supplies left in the world of these amazing tubes, so we can offer unprecedented matching and noise testing! Recommended by Dr. Z for all of his amps! Original equipment for Audio Research SP-6/8. Just $79.99 per tube (various brandings)! Balanced Triodes Just $89.99 per tube! Pre-war Yugo CV492 NOS NIB-Various brandings, all made in pre-war Yugoslovia) $79.99 per tube I love the Ei 12AX7 tubes of old, they were hands down the best sounding pre-amp tubes. Dr. Z Owner/Creator Z Amplification.