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In Reply to: RE: Will this work? Switching from 6.3 to 12.6 volts posted by Eli Duttman on June 12, 2017 at 00:01:16
Although it is just for the signal tubes.
The power trafo's "12" V. winding feeds the 12X4 rectifier and a doubler. The doubler feeds series wired pairs of signal tubes.
Series, parallel arrangement. I was just checking that, and on each circuit board, the 2 tube's heaters are in series, and the other circuit board is paralleled with the tube heater again in series. I have not noticed this type of an implementation in other preamps or amps. Is this kinda clever or mostly and economy move or both? I really did not notice this before and the PAS was the first tube preamp i owned over 30 years ago, which i was given by my father in law. And this explains why i always had trouble rebuilding that circuit, because i failed to notice that it was a voltage doubler and when rebuilding, its design always threw me off.
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