(Please don't move this. It's mainly about 'general' topics).. ![Smiley :)](https://www.eevblog.com/forum/Smileys/default/smiley.gif)
The "All American Five" refers to the mass produced valve radios, by very many manufacturers, from the 1930's. Apart from the standard 5 tubes & their functionality, their emphasis was on 'cheapness' of manufacture. There is/was NO power transformer, and relied on the American line voltage of 110/120-v to directly feed Plates (partly via resistors), and series connected tube 'heaters' of higher Filament Voltages etc., so that no mains transformer is/was needed. OK, I get it, but half the time, one ended up with a 'Live' Chassis for the uninitiated!? ![Tongue :P](https://www.eevblog.com/forum/Smileys/default/tongue.gif)
So many times, I've seen ccts where a 'power' switch, if any, actually switches the Neutral! The VAST majority of power plugs I've seen in America have only 2 pins, and no 'Earth' pin. Now I know that most 'modern' plugs/sockets there now are 'polarized' by way of a slightly wider pin, but still with no Earth?? I understand too that this is 'just' 110v, not 240v like in Australia, but I don't understand the attitude. I see numerous Youtube videos where people in the U.S. plug equipment into un-switched outlets on their bench. Ok, YOU might have wired it correctly. ![Sad :(](https://www.eevblog.com/forum/Smileys/default/sad.gif)
In Australia, we MUST have an Earth too, unless the device/machine is 'Double-Insulated', like a certain hair dryer etc. It just seems that America is more blase' about Neutrals & Earthing ?? (And yes, I understand about isolation transformers & isolated Variacs etc.) ![Phew :phew:](https://www.eevblog.com/forum/Smileys/default/phew.gif)
(Please don't move this. It's mainly about 'general' topics).. ![Smiley :)](https://www.eevblog.com/forum/Smileys/default/smiley.gif)
The "All American Five" refers to the mass produced valve radios, by very many manufacturers, from the 1930's. Apart from the standard 5 tubes & their functionality, their emphasis was on 'cheapness' of manufacture. There is/was NO power transformer, and relied on the American line voltage of 110/120-v to directly feed Plates (partly via resistors), and series connected tube 'heaters' of higher Filament Voltages etc., so that no mains transformer is/was needed. OK, I get it, but half the time, one ended up with a 'Live' Chassis for the uninitiated!? ![Tongue :P](https://www.eevblog.com/forum/Smileys/default/tongue.gif)
So many times, I've seen ccts where a 'power' switch, if any, actually switches the Neutral! The VAST majority of power plugs I've seen in America have only 2 pins, and no 'Earth' pin. Now I know that most 'modern' plugs/sockets there now are 'polarized' by way of a slightly wider pin, but still with no Earth?? I understand too that this is 'just' 110v, not 240v like in Australia, but I don't understand the attitude. I see numerous Youtube videos where people in the U.S. plug equipment into un-switched outlets on their bench. Ok, YOU might have wired it correctly. ![Sad :(](https://www.eevblog.com/forum/Smileys/default/sad.gif)
In Australia, we MUST have an Earth too, unless the device/machine is 'Double-Insulated', like a certain hair dryer etc. It just seems that America is more blase' about Neutrals & Earthing ?? (And yes, I understand about isolation transformers & isolated Variacs etc.) ![Phew :phew:](https://www.eevblog.com/forum/Smileys/default/phew.gif)
The AA5s were more a thing of the 1940s on.
If you look at most published 1930s US radio designs, they used power transformers, with secondaries of from 285 to 385 volts "a side".
Factory made Radios were fairly expensive back then, & a lot of circuits were designed for a fair bit of output power for use with the fairly inefficient "Electrodynamic".speakers in common use.
After WW2, the USA manufacturers wanted to produce cheap radios.
For some reason, power transformers were expensive, & "series string" tubes fairly inexpensive.
This, along with the fairly low (then) 110v Mains supply, lent itself to the "AA5" design.
Other developments, like more efficient "Permag" speakers, & improvements in tube efficiency also contributed.
In Australia, the economics went another way:-
Tube factories had massively increased their production during the War, but virtually all the tubes they produced were in the heater voltage values of 1.5v, 2.0v, 3.0v, 6.3v (the vast majority) & 12v.
There were also, in the early days, many hundreds of surplus tubes on the market, mostly 6.3 volt heater types
Higher voltage heaters suitable for "series strings" were not normally made, & usually had to come from the USA, the UK, or Europe.
The higher Mains voltage in Australia also made the case for transformerless designs much less compelling .
Transformers for domestic radios were neither excessively large or heavy, nor, in the Australian context, expensive.
The upshot was what became fairly standard in this country----- a 5 "valve" "mantel" radio using a power transformer, a tube rectifier, a mixer, one stage of IF gain, then a detector/audio driver stage (a "double diode, hi mu triode") & an audio power tube(usually a beam tetrode of the 6V6/ 6AQ5/6M5 ilk.
There were a few "transfomerless" radios around----some custom made. for the few remaining DC Mains Supplies.
Of these, some were 110v DC, & the relatively simple "AA5"type circuit could be used.
Others were 240v DC, & the radios were messy things with series resistors, "barrettors", etc.
Transformerlesss designs were dubbed "death radios" & loathed by radio servicemen.