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Push-Pull A2 6A3/300B Amplifier and Power Supply

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Push-Pull A2 6A3/300B

This amp has great specs, produces twice the power from your favorite tube and is simple to build. But you will need to decide which power transformer to use, both have identical performance but one runs cooler than the other because of the laminations. Then select which output transformer you’d like, our standard copper wound or the new PSSS which gives silver performance at a fraction of solid silver price. Read Jack’s comments at www.electra-print.com->Tech Blog->Spring 2007->Class A2 Operation for a description of this new transformer. You can find a list of the Electra Print transformers needed to build this amp below the schematics.

  • 50 watts output
  • .15% THD
  • -1db 15hZ 40 kHz
  • .7v to full output

Push-Pull A2 Amplifier

Push-Pull A2 Power Supply

Constructor Note: Capacitor 470uf/450v connected from the center tap of the output transformer must be changed to a higher value than illustrated in the schematic. Issue being that there is a 650v inrush at turn-on. To take this voltage, I suggest substituting the single electrolytic capacitor with a pair in series, along with bypass resistors, as done in the filter power supply. This will give the security of a 900v rating. If an oil capacitor is used, the inrush voltage will not be an issue. Following turn-on, the voltage on this capacitor runs at about 425v during normal operation.

Transformer prices:

PPA2 Power M19 lamination$225.50Standard Laminations
PPA2 Power M6 lamination$181.50Cool operation
PPA2 Output$269.50Standard copper
PPA2 Output PSSS$565.50Partial Silver Stranded Secondary
A2LD-7 Interstage $104.50 Constant load driver
High Voltage Choke $37.50  
Filament Choke 3A$26.50 Note: new value

All designs are the sole property of Electra-Print Audio Company with all rights reserved worldwide. Licensing is available for commercial use.

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