Perhaps the slightly misleading title will catch some attention😀
I say "misleading" because there is no ratings to be found on this particular tube. Let's start from the beginning: A couple of decades ago when I was new to this hobby, I bought a large stash of NOS 12A6 metal cased tubes from a surplus dealer for very little money. I still have at least a couple of dozens of them left plus a some well suited mains transformers with 12V heater windings and a pair of OPTs that would be a perfect match for a 12A6 parallel push pull project.
The thing that bothers me a little bit is that those OPT's have 15% CFB windings which will put some voltage swing on the cathodes, 40Vpp or so att full power.
Most tubes can take +-100V or so between heater and cathode but the 12A6 datasheet states:
"In circuits where the cathode is not directly connected to the heater, the potential difference between heater and cathode should be kept as low as possible".
There´s not much practical information about the 12A6 online, this is a tube that suffers from seriously low Audiophile Swag, but some of the old Heathkit A7 schematics shows 12A6s being operated with grounded heater windings while the cathodes are at 20V or so.
I say "misleading" because there is no ratings to be found on this particular tube. Let's start from the beginning: A couple of decades ago when I was new to this hobby, I bought a large stash of NOS 12A6 metal cased tubes from a surplus dealer for very little money. I still have at least a couple of dozens of them left plus a some well suited mains transformers with 12V heater windings and a pair of OPTs that would be a perfect match for a 12A6 parallel push pull project.
The thing that bothers me a little bit is that those OPT's have 15% CFB windings which will put some voltage swing on the cathodes, 40Vpp or so att full power.
Most tubes can take +-100V or so between heater and cathode but the 12A6 datasheet states:
"In circuits where the cathode is not directly connected to the heater, the potential difference between heater and cathode should be kept as low as possible".
There´s not much practical information about the 12A6 online, this is a tube that suffers from seriously low Audiophile Swag, but some of the old Heathkit A7 schematics shows 12A6s being operated with grounded heater windings while the cathodes are at 20V or so.
Absolute Max heater to cathode voltage for 12a6 is 100 volts, the so called design center max is 90 volts dc. See attached datasheet.
Wow, thanks! I´ve never seen that datasheet before. Very similar to the one here http://www.r-type.org/exhib/aaa0599.htm butwith real Vhk ratings, excellent!
It still recommends a direct connection between heater and cathode but with an absolute max rating of 100V I guess +-20V should be perfectly fine.
It still recommends a direct connection between heater and cathode but with an absolute max rating of 100V I guess +-20V should be perfectly fine.