For Sale: Matched set of six four 1958 vacuum tubes.
If you are reading this you probably already know but the 12DT7 is a quite rare upgrade to the 12AX7 tube and can be used as a direct replacement in any equipment that uses the 12AX7 or 12AX7A. Made only by Raytheon and only for a short period of time in the late 1950's and 1960's.
Tested audibly in a 1950's preamplifier on all 3 channels and sound quality was uniformly excellent. No distortion, hum, or static on the phono, tape, or radio channels. Also checked with a CD player as source and they really made the CD audio sparkle in my opinion. Full range and very pleasant sounding. These tubes are almost certainly original to the 1950's Madison Fielding 340 preamp they came out of which spent it's entire life in a large floor console in a climate controlled living room. The difference in test results on the tubes is probably due to the differing amount of time the previous owner spent listening to the turntable, reel to reel tape, and FM tuner.
All tubes carefully tested on a B&K 747B tube tester. On this tester anything that tests under 55 is considered bad and should be replaced.
Test results:
-
- 75/85
- 75/80
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- 78/77
- 75/68
The yellow print lettering on the tubes is in pretty amazing condition, see photos. I should have some video of the Madison Fielding being tested with these tubes still in place, if you need to see it let me know and will check.
More higher resolution photos are available on request.
Send city and zip code for a ship quote- should be between $5.99 and $7.99 if you are located in the United States. (Dec. 2023).
