Output Stage in MJ Question

[dsavitsk]

Morgan Jones, 3rd ed, fig 6.11, is an output stage like the attached. He suggests that while the drive requirements are high, that a possible advantage is that DC will cancel allowing use of an ungapped transformer. It has been suggested to me that the stage won't actually work as AC will cancel as well. That seems right as I look at it one way, but maybe not right another way -- anyone know for sure. Is this a mistake?

[Robert McLean]

I did a quick SPICE simulation, and it is telling me that you are correct, the AC does cancel, there is no output produced. The circuit only works if you change the input windings to be in phase.

I find this puzzling since in the version of Morgan Jones that I have, he says this circuit was actually used in an amp called the Michaelson & Austin TVA10. So how did that amp work ? What are we missing here ?

[Robert McLean]

I did a web search for the TVA10 amplifier, and came up with many hits. Here is one link to the schematic,

http://www.ampslab.com/vintage_micha...stin_tva10.htm

which shows a much more complicated arrangement than that in MJ. It has push pull transformers on the plates, push pull transformers on the cathodes, and inputs also to the grids.

I can only guess that MJ just wanted to give a simplified example to show that dc current could be cancelled out, and did not intend that the circuit be taken too literally ??

[kenpeter]

Refer back in time to thread entitled:

Concertina Parafeed, or How to mess with OldEurope's mind...
Concertina Parafeed, or How to mess with OldEurope's mind...