Low filament current tubes

[neazoi]

Hello,
I need a miniature dual triode type tube like the size of ECC83, but one which uses low filament current. 300mA is too high. the lowest the better.

Do you know of any types?

 

[Zen Mod]

connect two heater halves in series , fed them with 12V6/150mA

so:

heater - pins #4 & #5 , leave pin #9 unconnected

pins - look clockwise from base of tube

left one is #1

 

[neazoi]

Anyone with even less fillament current?

 

[Zen Mod]

ECC83 is already "weak" tube ;

why you need even weaker ..... that will be result of smaller current through filament - whatever tube you find

 

[Bigun]

Lowest filament current - use a JFET. No seriously, they have nice transfer curves and if you are willing to pay, they can be had for use at high voltage.

 

[kevinkr]

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.

 

[bob91343]

You could use the tubes designed for portable radios, back in the day. They generally draw 50 mA at only 1.5 V.

Otherwise I think you are stuck.

 

[neazoi]

I would like the size and look of the glass envelope to be like the ecc83...
are there any lower current versions?

 

[wa2ise]

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.

 

[neazoi]

no problem, I need them for computer logic

 

[ray_moth]

There's also the UCC85, 26v heater @ 100mA or the UCC88, 21v heater @ 100mA.

 

[Arnulf]

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.

 

[neazoi]

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...?

 

[Arnulf]

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.

 

[neazoi]

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!