Hoffman Amplifiers Tube Amplifier Forum
Amp Stuff => Tube Amp Building - Tweaks - Repairs => Topic started by: Jonas on January 03, 2024, 10:38:57 am
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I have a couple odd tubes (at least to me) curious if anyone has any experience with these?
12BH7A - Twin Triode
EF89 (6DA6) - High Slope Vari-mu RF Pentode
12HL7 - Sharp Cut-off Pentode
12B4A - Low-mu Triode
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The old radar system I worked on for 30+ years had plenty of 12BH7s. They were used almost exclusively for video and/or trigger cathode follower line drivers.
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If you do a search here on the site you can find some thread discussing about 12BH7 tubes
Franco
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Thanks! I looked at the 12BH7A pinout and also did a quick search on line. I found a few references comparing it to the 12AT7. When I get a chance I will do some tube swapping on an amp I have here.
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12BH7 is closer to a 12AU7 than a 12AT7.
12BH7 gain is 16.5.
12AU7 gain is 19.5.
12AT7 gain is 60.
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About EF89 seems in some way it is usable
https://www.youtube.com/watch?v=DWu5zhL5VmA (https://www.youtube.com/watch?v=DWu5zhL5VmA)
(https://el34world.com/Forum/index.php?action=dlattach;topic=31177.0;attach=110828;image)
(https://el34world.com/Forum/index.php?action=dlattach;topic=31177.0;attach=110832;image)
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Also 12B4A seems usable
https://it.aliexpress.com/i/1005004636971693.html?gatewayAdapt=glo2ita (https://it.aliexpress.com/i/1005004636971693.html?gatewayAdapt=glo2ita)
(https://i.imgur.com/9rcIpHy.jpg)
Franco
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The old radar system I worked on for 30+ years had plenty of 12BH7s. They were used almost exclusively for video and/or trigger cathode follower line drivers.
I also worked in Radar Systems at Hughes Aircraft in Fullerton, CA until early 90's
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thanks sluckey i see that now on the TDS
thanks for the schematic - I will keep them around for future projects
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The old radar system I worked on for 30+ years had plenty of 12BH7s. They were used almost exclusively for video and/or trigger cathode follower line drivers.
The McIntosh MC-30 used the 12BH7 as a push-pull driver tube.