Power transformer question (center-tapped power supply)

thorpej

Super Member
I'm penciling out a project where I plan to use a center-tapped power transformer and FWBR configuration to produce 600V and 300V rails. The Edcor XPWR182 is almost right -- 225-0-225 @ 500mA, with a nice 12.6Vct 4A heater winding. But to get the voltages I want, I really need 235-0-235. Edcor makes the XPWR258 which has that configuration available (it's actually 345-235-0-235-345), but it only carries a 300mA rating, and the heater windings are weak-sauce (6.3Vct @ 2A).

The amp will draw approximately 280mA plate current + 30mA screen current + 22mA front-end current at full power (== 332mA). What I'm wondering is, because the 30mA screen current and 22mA front-end current are going to be coming from the 300V rail, will they be placing less load on the transformer and, as such, the 300mA rating of the XPWR258 won't be an issue?
 
Its still going to have total current load on the transformer no matter where you tap things from. Personally I'd give up the 10v and keep the current rating. More current reserve in the transformer usually produces a more stable supply that won't sag as much under load anyway.
 
Yah, ok, fair enough. I was thinking more along the lines of "total VA on the secondary", but I still think I can squeak out the 50W/ch target from this project with the XPWR182.
 
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