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Gary Albach
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Hi Les – instead of replacing the field coil from an electrodynamic speaker with a resistor, I have had good results using a solid-state field coil replacement. Here is a link to the circuit and original construction article published by the Antique Wireless Association:
As stated in the article, the circuit provides 60 Hz ripple suppression in excess of 60 dB, far in excess of the original field coil acting as a choke.