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Old 9th July 2007, 07:58 PM   #1
engels is offline engels  Israel
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Default 150V plate output tubes

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.
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Old 9th July 2007, 08:22 PM   #2
bigwill is offline bigwill  United Kingdom
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6c33c / 6c41c
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Old 9th July 2007, 08:27 PM   #3
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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.
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Old 9th July 2007, 08:36 PM   #4
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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!!

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Old 9th July 2007, 09:23 PM   #5
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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.
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Old 9th July 2007, 09:46 PM   #6
Tweeker is offline Tweeker  United States
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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.
Be sure your foil hat has a good low impedance ground.
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Old 9th July 2007, 10:00 PM   #7
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The 6K6 looks like another good tube. Same goes for the 6AS7.
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Old 9th July 2007, 11:17 PM   #8
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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!
Eli D.
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Old 10th July 2007, 12:20 AM   #9
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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.
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Old 10th July 2007, 02:50 AM   #10
wa2ise is offline wa2ise  United States
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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.
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