[MrFixr55]

Hi John,

Just put it in. Sorry, I wrote in "Quick Reply", which does not allow for attachments. I had to do a Full Edit. It is there now. Hope that helps.

Interestingly, output transformers were not popular with radios of this vintage. These early cone speakers had high impedance, high resistance electromagnets (as opposed to the much lower impedance voice coil in the dynamic speaker. In battery sets, the speaker was placed directly in the plate circuit of the output tube. However, in your 512, the RCA Radiola 18 and similar Atwater Kent models of the time, LC coupling was used. A choke was in series between the output tube plate and B+. A 0.5uF capacitor was connected between the plate of the output tube and one terminal of the speaker. The other terminal of the speaker usually connected to the filament center tap either directly or through a resistor.

Hope this helps.