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Old 20th Nov 2020, 10:41 am   #1
lloydwells
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Default Circuit wanted for 1920s style Battery powered Amplifier

Right I have a very nice two valve radio from 1925 I want to build a seperate amplifier for it using 2v battery valves anyone built anything like this or in possession of an original design for one ??
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Old 20th Nov 2020, 11:16 am   #2
GrimJosef
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Default Re: Circuit wanted for 1920s style Battery powered Amplifier

It's claimed that although push-pull was known about by this stage, the first commercial PP radio amp only appeared in 1924 https://en.wikipedia.org/wiki/Push%E2%80%93pull_output. A more primitive single-ended amp is detailed in this series of Godfrey Phillips cigarette cards, including all the instructions for building one http://www.r-type.org/articles/art-028.htm. I like the way that the two cards which cover the subject of the valve more or less boil down to saying "Get a valve" .

Cheers,

GJ
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Old 20th Nov 2020, 11:48 am   #3
peter_scott
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Default Re: Circuit wanted for 1920s style Battery powered Amplifier

You could just build the AF parts of a WW project like this.

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Old 22nd Nov 2020, 11:27 am   #4
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Default Re: Circuit wanted for 1920s style Battery powered Amplifier

There are pages and pages of ads first, but if you scroll down to the 12th page, that’s where the circuit diagram is. It is marked in the upper left hand corner as (page) 3.
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Old 23rd Nov 2020, 8:46 pm   #5
lloydwells
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Default Re: Circuit wanted for 1920s style Battery powered Amplifier

I'd quite like to make a push pull amp struggling to find a.schematic for push pull using directly heated battery Triodes though.
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Old 23rd Nov 2020, 9:15 pm   #6
Ed_Dinning
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Default Re: Circuit wanted for 1920s style Battery powered Amplifier

Hi lloyd, have a look at QPP circuits. They use a single valve with 2 electrode assemblies inside

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Old 23rd Nov 2020, 9:18 pm   #7
peter_scott
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Default Re: Circuit wanted for 1920s style Battery powered Amplifier

How about these?
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Old 24th Nov 2020, 9:00 am   #8
saddlestone-man
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Default Re: Circuit wanted for 1920s style Battery powered Amplifier

Looks like a worthwhile project.

Suitable output valves, even twin triodes and QPP twin pentodes, are fairly easy to find. Suitable driver and output transformers with intact windings are harder to find.

Unless you intend to build the transformers yourself, I suggest you look for the transformers first.

best regards ... Stef
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Old 25th Nov 2020, 8:39 pm   #9
lloydwells
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Default Re: Circuit wanted for 1920s style Battery powered Amplifier

Yes I have some transformers non push pull so I think we'll stick to single ended
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Old 26th Nov 2020, 5:03 pm   #10
lloydwells
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Default Re: Circuit wanted for 1920s style Battery powered Amplifier

OK I'm still really struggling with this one I can find load of single valve designs bit for the sake of vanity and looks I really want two valves they're going to be visible ideally what I want is something switchable between one valve and two I have a pile of good period ( ish ) 2 volt Triodes pm2 PM2a p220 and some 220-ot to play with I've got 2.5:1 4.5:1 and 5:1 transformers sitting about and a fair selection of period caps grid resistors and switches terminals Rheostats etc.

So the aim is to make something that looks good and works fairly well.
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Old 26th Nov 2020, 10:26 pm   #11
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Default Re: Circuit wanted for 1920s style Battery powered Amplifier

If you cannot find a couple of vintage transformers with with centre tapped windings it might be worth the effort to strip a couple of old coupling transformers and rewind them with centre taps. There are plenty of old coupling transformers available. Probably quite a few worthless ones with corroded (open) windings.

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Old 26th Nov 2020, 11:20 pm   #12
Restoration73
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Default Re: Circuit wanted for 1920s style Battery powered Amplifier

This set has a choice of using a single or two audio valves by switching and the info is
available "up top"
http://www.kbmuseum.org.uk/kb_images...set3a_late.htm
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Old 27th Nov 2020, 8:29 pm   #13
lloydwells
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Default Re: Circuit wanted for 1920s style Battery powered Amplifier

Well I found a circuit so I've started building it coming along quite nicely though I can't decide if the transformer should stay on top or go underneath I quite like the look of it up top.
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