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General Vintage Technology Discussions For general discussions about vintage radio and other vintage electronics etc. |
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19th Sep 2020, 10:42 pm | #21 | |
Moderator
Join Date: Mar 2012
Location: Fife, Scotland, UK.
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Re: PX4 substitutions
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David
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19th Sep 2020, 11:40 pm | #22 | |||
Heptode
Join Date: Jan 2006
Location: Todmorden, West Yorkshire, UK.
Posts: 870
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Re: PX4 substitutions
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20th Sep 2020, 12:18 am | #23 |
Octode
Join Date: Feb 2009
Location: Bletchley, Buckinghamshire, UK.
Posts: 1,219
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Re: PX4 substitutions
"Art and Science in Sound Reproduction" by F H Brittain, published by GEC in 1953, contains designs for three "basically similar" push-pull amplifiers. A 14W version using PX4, a 12W using triode connected KT66, and a 20/30W (from different HT voltages) with pairs of KT66.
There is a picture of the 30W amplifier, captioned as having been designed by Williamson for the MO Valve Co. I wonder if this is the publication being referred to? |
20th Sep 2020, 6:38 am | #24 |
Octode
Join Date: Dec 2017
Location: Morden, Surrey, UK.
Posts: 1,557
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Re: PX4 substitutions
That is the book - my memory failed me, as I said I can't find it now, haven't seen it for 30 odd years.
I remember the 30 watt amplifier, that must have been why I thought the whole thing was by Williamson. As I say, my Uncle built the PX4 version (and the pre-amp) which I later converted to the classic KT66 type. |
20th Sep 2020, 8:22 am | #25 | |
Heptode
Join Date: May 2017
Location: Konongo, Ghana
Posts: 514
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Re: PX4 substitutions
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1) The AL4 takes 1.75 A filament current against the PX4 taking 1 A. 2) The maximum anode dissipation of the AL4 is 9 W, that of the PX4 is 15 W. Problem 2) could be adressed by using the AL5 (Pa max. = 18 W), with the extra advantage that Ri of the AL5 in triode connection is about half of that of the AL4 in triode connection. But problem 1) would just get bigger because the filament current of the AL5 is 2 A. Beside that, the AL5 is harder to get than the AL4.
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