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Old 2nd May 2012, 12:43 AM   #1
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Default Alfred Morgan Tube Preamplifier

Does anyone have any experience with this Alfred Morgan preamp? I am looking for a my 1st preamp project and was wondering if this has been built and tested by any of the forum members.

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Old 2nd May 2012, 01:06 AM   #2
kevinkr is offline kevinkr  United States
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I'm going to move this to tubes / valves since I suspect it will get a bit more notice there..

I built one of his AM regenerative radio designs as a kid, worked fine.. Had fun building it with quite a lot of help from my father.. (I was 7 at the time.)

Have to ask what the intended purpose is, reliance on things like grid leak bias makes it more suitable for use with one Morgan's crystal radio sets.
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Old 2nd May 2012, 01:07 AM   #3
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Thank you.

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;cop: I'm going to move this to tubes / valves since I suspect it will get a bit more notice there..

I built one of his AM regenerative radio designs as a kid, worked fine..
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Old 2nd May 2012, 02:42 AM   #4
SY is offline SY  United States
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It will have an impractically high output impedance as well as too low an input overload for modern use. Perfect with his crystal radio and power amp. Not hifi but educational.

BTW, when I was a kid, I loved the Alfred P. Morgan books; my blessed wife has found and bought me nearly all of his science and electricity books over the past couple of years.
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Old 2nd May 2012, 02:54 AM   #5
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Thank you for the response. I am poking around for a tube preamp to build and this looked interesting. Good feedback concerning the preamp, thanks again.

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It will have an impractically high output impedance as well as too low an input overload for modern use. Perfect with his crystal radio and power amp. Not hifi but educational.

BTW, when I was a kid, I loved the Alfred P. Morgan books; my blessed wife has found and bought me nearly all of his science and electricity books over the past couple of years.
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Old 2nd May 2012, 10:13 AM   #6
DF96 is offline DF96  England
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500k is a bit small for grid leak bias so the bias point will almost certainly be sub-optimal! Severe distortion on all but the smallest signals is likely. To be honest, it does not look to me to be a well-designed circuit even for its (presumed) intended use of amplifying a crystal set.

You need to bear in mind that 'preamp' simply means an amp which comes before the main amp; it does not necessarily mean 'hi-fi stereo preamp' or even 'audio preamp'.
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Old 2nd May 2012, 04:49 PM   #7
kevinkr is offline kevinkr  United States
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<snip>

BTW, when I was a kid, I loved the Alfred P. Morgan books; my blessed wife has found and bought me nearly all of his science and electricity books over the past couple of years.
I used to have them all as a kid, in the move back from overseas or sometime afterwards they went AWOL.. I have the second one in the series picked up from a used bookstore. As I kid I used to dream of building what I now know is a death trap 50C5 PP amplifier - mains operated and nary an isolation transformer in sight.
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