[Amps] Push pull amps

[Mark, K5AM]

Push-pull is a nice method. The link below shows
a push-pull amp I built 59 years ago; it still runs
full power with the original Eimac tubes.

http://www.zianet.com/k5am/amp6mkw.html

73,

Mark, K5AM


On 2020-08-01 18:08, Victor Rosenthal 4X6GP wrote:
> I think the main reason they liked putting triode amplifiers in 
> push-pull was to simplify the neutralization. Of course it is possible 
> to neutralize single-ended amps with a bridge circuit or to use 
> inductive neutralization, but I think it's easier to obtain complete 
> neutralization with a push-pull circuit.
>
> The change came about with the popularity of tetrodes which are easy 
> to neutralize in single-ended configuration, the popularity of 
> pi-network output circuits, and the desire to get away from plug-in 
> coils (think about bandswitching a balanced tank circuit). Also, TVI 
> shielding was difficult with plug-in coils.
>
> I think probably the change happened after WWII, when surplus coax 
> became available. Shielded, single-ended circuits with pi-networks 
> running into coax-fed antennas became the hot setup.
>
> 73,
> Victor, 4X6GP
> Rehovot, Israel
> Formerly K2VCO
> CWops no. 5
> http://www.qsl.net/k2vco/
> On 01/08/2020 20:02, Tom Osborne Sr. wrote:
>> I recently purchased some QST's from '47, 49, and 50.  I notice a lot of
>> transmitters and amps back then used 2 tubes in push-pull circuits, 
>> instead
>> of parallel, like we mostly do now.
>>
>> What was the idea behind push pull compared to parallel, and when did 
>> the
>> change take place?  Thanks and 73
>> Tom W7WHY
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