150V plate output tubes

[engels]

I've got a couple of beefy 230:115V transformers which I wanted to put in use. Do you have any suggestions on power tubes which may work good with low voltages?

I've got a couple of SE output transformers with 10K and 5K primaries.

Of course, more output is better, ST octal is better than 9-pin envelope, cheaper is better than expensive etc. I thought about 6G6G output but 1W is not that much.

 

[bigwill]

6c33c / 6c41c

 

[richwalters]

Don't ignore the idea of using secondaries configured as voltage doublers or even triplers, if windings are suitably current rated. Many early amp designs used this technique using cheaper TV components. There was one in particular..name lost..perhaps other members know.

Hint: if there is enough room between bobbin and outer core limb on an E/I core one can often wind a few turns for the heater. Even easier with toroid without centre.
richj

 

[Craig405]

Make sure they arent auto transformers, if the secondary has a detectable resistance to the primary you are basically tapping straight from the mains without any protection!!

Regards
Craig

 

[Tom Bavis]

6Y6G is cheap enough, and can give a few watts at 160V B+... but I like the idea of the voltage doubler, which will give you a lot more choices, and let you use a 5K transformer (most tubes at 160V will want 2K or so...).

Be sure they are ISOLATION transformers, as already suggested.

 

[Tweeker]

You can also series connect the secondaries for more voltage since you have two.

Also, the two secondaries can be series connected for a 230V winding that can be used as a primary, giving you two 230V secondaries to play with.

 

[astouffer]

The 6K6 looks like another good tube. Same goes for the 6AS7.

 

[Eli Duttman]

Engels,

The nnL6 (not 6L6) group was intended from the start for a "150" V. B+ regime. Tom Bavis is correct about a low impedance O/P trafo being necessary.

I LIKE the voltage doubler idea. That brings "El Cheapo" into play. Grinding one's own axe is always fun. You said Octal and inexpensive. Build with NOS 12V6s!

 

[Tom Bavis]

The tubes to which Eli refers are: 6W6, 6DG6, 12W6, 12L6, 25L6, 35L6, 50L6, and similar ones in different bases. Not commonly found in "ST" style, though they're quite common and cheap. 25C6G and 50C6G are not common, but there's no demand, so they're quite cheap. They're higher heater voltage versions of 6Y6.

 

[wa2ise]

There's always the 50C5, a 7 pin miniature version of the 50L6, though it won't take B+ over about 160VDC.

At my web page where I built a tube amp in a Sony receiver using such tubes.

 

[wrenchone]

6CW5 or a small sweep tube, anyone? Sweep tubes generally have a high plate current capability at low plate voltage, so does the 6CW5. If you don't mind a Compactron, the 6LR8 and 6LU8 have a fairly high mu triode in the same package as a hefty beam tube.