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Old 8th Oct 2019, 5:26 pm   #18
WB6NVH-GEOFF
Tetrode
 
Join Date: Aug 2013
Location: Monterey, California USA
Posts: 51
Default Re: Hallicrafters S27

The 500 and 5000 Ohm outputs are both speaker outputs, not headphone and not line outputs. Yes, 500 Ohms was a common line output impedance but there is also something called "line level" which this is not. This is speaker level audio.

In the early 1930's, 5000 Ohms was a common speaker line impedance, probably with magnetic speakers, hence this impedance being found here.

The way you use this today is with a matching transformer to 4-8 Ohms and a modern speaker. I usually use a 70 Volt public address "ceiling speaker" transformer with the correct tap selected, as they are cheap and easy to find. In a pinch a 6 volt filament transformer run "backwards" connected to the 500 Ohm output will also work.
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