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merlin el mago 27th December 2010 10:32 AM

PP to parallel
Please need help, how can do to convert this PP schematic in parallel?

markusA 27th December 2010 10:56 AM

Please be a little more specific about what you want?
What do you want to achieve?
What is the purpose?

Vinylsavor 27th December 2010 10:57 AM


What exactly do you want to achieve? The circuit you've shown is not PP and what do you mean by 'parallel' ?


revintage 27th December 2010 11:13 AM

I am sure merlin PP refers to that this circuit is called "Shunt Regulated Push Pull". To parallell the two triode-halves to get a conventional CC-stage is no big deal.

merlin el mago 27th December 2010 11:38 AM

@ markusA & Vinylsavor
I want to convert the push pull in two triode-halves paralleled with the same valve.

Isn't any advantatge to convert the push pull in parallel triode? could you elaborate?

Vinylsavor 27th December 2010 12:44 PM


Try this:

connect both systems in parallel, use half the cathode resistor value which is in now and double the cathode bypass cap. Connect the output coupling cap to the anodes and a plate resistor 5k/10W from anodes to B+.

Alternatively you can try just single systems: Disconnect the upper system in the SRPP stack, or better ground all unused elements. Leave the cathode R and C and use a 10k plate load resistor.

Best regards


revintage 27th December 2010 12:46 PM

Try if you like SE by moving the output cap to below the upper 330ohm. This way the lower triode will be loaded by, in the ballpark of, 20k. This if we assume Ri being just below 10k at this low Ia.

About parallelled 6922 halves I have no idea if it sounds good, havenīt tried. But you have the answer about how to do in Thomas post above. (Our posts crossed)

Vinylsavor 27th December 2010 12:47 PM


I forgot to add: you should then also change the bias voltage of the heater. As a first try you can simply reference the heater to ground. Or change the voltage divider which elevates the heater to values which will bring it ti about +25V.


Vinylsavor 27th December 2010 12:49 PM

I couldn't make out the B+ voltage in the schematic, it is difficult to read. For my suggested mod it should be 180...


merlin el mago 27th December 2010 01:31 PM

Sorry I forgot to told you that the heater now isn't shunt type, each tube has is own heater. Voltage B+ before 4k7 is 180V. Could you draw & post an schematic with changes & values to do?

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