The description of the input circuitry sounds as it could be configured for a carbon microphone.
Al
Just been looking at whats connected to what and its got a clever little setup that will only fire the generator when speakers are connected 
Regards
Luke
So the relay does a bit more than just stopping the switch carrying the start up currant.
Carbon microphones did take a bit of power so that is what that huge resistor was all about.
The rotary converter, the (no)speaker protection and the microphone input circuitry makes me think that these amplifiers are meant for portable P.A. work.
Al
Big horn speakers on the car/van roof!
Yes indeed Michael. I would be interested to find out what the current draw on the 12V supply would be on these. In their day the average car dynamo probably only produced around 20 amps so I would imagine that there was more driving around recharging the battery than broadcasting.
Al
Double the current for inefficiency, then assume 240V HT, so x40 for 12V. Add the heater current of 1/2 the valves.
Maybe 70mA HT average? So 2.8A + 0.9 + 0.3 = 4A approx?
That's 48W to get maybe 15W of class B push Pull Audio, seems about right.
Hi all,
My first post because I saw this set of images on Google.
Does the author of this thread still post ?
Would love to chat about this find.
I believe this is the same as an ardente amplifier, used during ww2 for loud speaker systems.
I am trying yo track one down for my own collection
Thanks
Alan
Hi Alan, the original author of this thread rarely if ever visits the forum, and this thread is over 8-years old. I have repeatedly tried contacting him via text, FB messenger and e-mail since February 2021, none of my messages have resulted in a reply.
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