Purchased for my Primaluna Prologue Four amp and performed exceptionally well. Both are in great shape with plenty of life left in them. No longer need them so they must go to a new home/amp.
This matched pair RCA 17MM plate, slant-, square-getter, black-plate 12AX7 dual triodes was tested on a Hickok 600A for shorts, gas and transconductance. There were no shorts or gas. Transconductance measured 1000/1000 micromhos for Tube One and 1020/1100 micromhos for Tube Two. (12AX7s typically test within one standard deviation of 1250 micromhos).
"They are dead quiet when the preamp is muted and have excellent frequency response, sound-staging, and dynamics. These are among the earliest 12AX7s made and both appear to have been made in 1956, perhaps at the very moment President Eisenhower was golfing..."
1 pair of 12ax7s RCA
Re: RCA 12ax7 Black Plate Vacuum Tubes 17mm Pair
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