Power transformer as audio transformer
You can avoid direct current from flowing in the filament transformer used
as an output transformer by using a choke with sufficient inductance to act
as a load, then capacitive coupling the filament transformer to transform
impedances only. That way, the filament transformer is only used with ac.
This method is often used with modulation transformers, to prevent dc from
saturating the core of the modulation transformer.
73, Colin K7FM
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