The tube were tested on my TV-7/U at 34-36/32 min good (65%)What you see is what you get.
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A tube was considered acceptable/new/ passed standards if it tested between the specified minimum and maximum on a tube data sheet or the minimum value specified on the tester (tv7 is minimum is 65%).
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As the RCA manual states - the characteristics may fall in a range above or below the bogey values when testing tubes. It’s speculated that the way the side getter is mounted to the plates contributes to the low microphonics on these tubes.
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The pictures shows a 50s RCA 12ax7 Tall Gray plate Bent Square Foil getter 100/100 a side NOS! Last picture show the box with the "12ax7" stamped on the end. Tube Tester Scale reads. So lets say on a scale of 1-10 -- Any tube testing 7 or below, was either sold to the secondary market or if testing low enough.
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The most distinctive sound feature of the Heerlen ECC83's is the transparent, natural and expansive midrange presentation, with a slight touch of warmth that illuminates your music. Every piece of music you play through these tubes sounds like from a vinyl record, whether your sound source is phono or not.
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Tested on Amplitrex AT-1000 tube tester (fixed bias mode). Two Raytheon 12AX7 tubes. triode #1 = 1200 micromhos @. 9mA plate current emissions / 92.2 Mu gain. Triode #2 = 1200 micromhos @. 7mA plate current emissions / 92.2 Mu gain.
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