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Unlikely that you will find what you are looking for in a standard 9 pin dual, but if you are willing to consider some oddball subminis you might find something. Is this as a sub for a 12AX7A (if so you are out of luck) - otherwise you can design something to use some of these submini direct heated pentodes (DHP) instead:
6088 DHP with 20mA @ 1.25V http://www.mif.pg.gda.pl/homepages/frank/sheets/138/6/6088.pdf
6418 DHP with 10mA @ 1.25V http://www.mif.pg.gda.pl/homepages/frank/sheets/127/6/6418.pdf
Steve Bench used these in a battery operated pre-amp with reasonably good results. They can also be triode connected.
6088 DHP with 20mA @ 1.25V http://www.mif.pg.gda.pl/homepages/frank/sheets/138/6/6088.pdf
6418 DHP with 10mA @ 1.25V http://www.mif.pg.gda.pl/homepages/frank/sheets/127/6/6418.pdf
Steve Bench used these in a battery operated pre-amp with reasonably good results. They can also be triode connected.
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are there any lower current versions?
There's the 20EZ7, 100ma albeit at 20V. And the pinout is different.
http://www.mif.pg.gda.pl/homepages/frank/sheets/049/2/20EZ7.pdf
Those DHT submini's tend to be microphonic, however.
no problem, I need them for computer logic
Pay attention to Vkh(max), Greece hass 230V mains IIRC so you can't save on the heater supply iron if that was your plan (this would make sense in computer application) as most small tubes only have ~100V rating.
Pay attention to Vkh(max), Greece hass 230V mains IIRC so you can't save on the heater supply iron if that was your plan (this would make sense in computer application) as most small tubes only have ~100V rating.
If I have 10 tubes with 300mA@6v this will require more iron than the 150mA@12v, if both at the same input voltage of 220v...?
If I have 10 tubes with 300mA@6v this will require more iron than the 150mA@12v, if both at the same input voltage of 220v...?
It is not the question of current, it is the question of voltage. I take you want to run series chains of heaters to save on supply (this is very much like LED illumination, if you want any decent volume of light you need many ELDs and you end up running entire chain in series). 10 x 6.3V = 63V, 10 x 12.6V = 126V. Topmost tubes in series would exceed Vhk(max) if they had their cathodes at same potential as other tubes.
It is not the question of current, it is the question of voltage. I take you want to run series chains of heaters to save on supply (this is very much like LED illumination, if you want any decent volume of light you need many ELDs and you end up running entire chain in series). 10 x 6.3V = 63V, 10 x 12.6V = 126V. Topmost tubes in series would exceed Vhk(max) if they had their cathodes at same potential as other tubes.
Of course! running a pair of tubes in series solves the problem! 12v still at 300mA for 2x 12ax7 in series (6v on each of them).
Thanks!
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