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Maximum DC Bias Re: Universal Audio Transformer
2/7/2005 8:52:22 AMJack

In selecting a universal push pull output transformer, what should the rating of the transfomer be for 12A tubes in push pull, regarding maximum DC bias?
2/8/2005 12:26:49 PMJohn McPherson
Just match to the ratings of the tube. For the 12A/112A Your maximum plate voltage is 180 volts @7.7 Milliamps and plate impedance is 4700 Ohms.

If you are selecting for a push pull circuit, double that resistance value because the transformer will be rated across the entier primary winding.

Generally, if you are not pushing the transformer near the maximum current, the voltage could be even higher as long as the tube is able to operate in that range as the transformers of new manufacture are "HiPot" tested, which means that the insulation on the wire is good to at least 1000 volts.


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:In selecting a universal push pull output transformer, what should the rating of the transfomer be for 12A tubes in push pull, regarding maximum DC bias?

2/8/2005 10:04:42 PM
Thank you John.

:Just match to the ratings of the tube. For the 12A/112A Your maximum plate voltage is 180 volts @7.7 Milliamps and plate impedance is 4700 Ohms.
:
:If you are selecting for a push pull circuit, double that resistance value because the transformer will be rated across the entier primary winding.
:
:Generally, if you are not pushing the transformer near the maximum current, the voltage could be even higher as long as the tube is able to operate in that range as the transformers of new manufacture are "HiPot" tested, which means that the insulation on the wire is good to at least 1000 volts.
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::In selecting a universal push pull output transformer, what should the rating of the transfomer be for 12A tubes in push pull, regarding maximum DC bias?



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