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Saturday, December 21, 2013

Push Pull Output Transformer



Push Pull Output Transformer

We’ve discussed a lot about single ended output transformer. Now it is turn to look at push pull output transformer. 

Everybody says that single ended output transformer is very difficult to make. We can tell you that push pull output transformer is even more difficult! Basic single ended output transformer only needs a single winding at the primary. Basic push pull output transformer needs 2 identical primary windings to connect to two tubes, terminated at a single end for connecting to the B+ high voltage. 

Balance of the 2 windings need to be perfect for balanced operation, and the coupling of these 2 windings with secondary windings need to be closely matched and tight to obtain perfectly matched electrical characteristics (impedance, coupling, primary inductance, leakage capacitance and etc)  for both push and pull tubes. Then, only the output waveforms will be nice, meaning good frequency response on all audio frequencies, and the sound will be good. This is something feedback cannot help to improve. 
Push Pull with constant current sink
A constant current sink + potentiometer for cathode bias of a push pull amplifier will help in balancing the current between the 2 tubes but that is a limitation to how much this can help if the push pull output transformer is flawed in the first.

If a push pull amplifier does not sound good, it is probably not the circuit or the tube, but the push pull output transformer quality (improper balance on primary and secondary windings, other other issues) that is affecting the output quality. 

Therefore, designing and making push pull output transformer is actually more difficult than single ended output transformer. 

So, do we deserve to charge higher for push pull output transformer? Go figure!  

J&K Audio Design
21/12/2013

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* Finished amplifiers, DACs, audio gadgets, upgrades and repairs - this is not our core business and we do it out of passion. We do not have fixed models, fixed price and we customize for each individuals. The sky is limit of creativity.

* Our product lines are always improving and increasing. If you do not see what you want, contact us!

* Please email for volume discounts, distributor and OEM pricing.

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