12AX7 DUAL TRIODE AS CLASS A AMPLIFIER

409

05:35:28

Audio in from lower left through connected grids of 12AX7 dual triode.  Signal out through two connected tube plates.  Above transformer is automotive ignition coil with B+ input of 100 to 300 DC volts  (apparently coil secondary ). Input from tube plate to coil + (battery) and one side of 8 ohm speaker.  Second speaker wire connected to coil - (distributor) connection on coil.  High voltages require caution and proper insulation on these projects.

published 11 years ago

hurz

11 years ago

According to a datasheet i found, 12ax7 is heated in serial with 12.6V or in parallel by 6.3V and in both combinations with 300mA.

mikey5869

11 years ago

I dont mean to be funny hurz but how can it be 300mA for both combinations? Surly the impedance would double in series so even doubling the supply voltage would half the current draw?

hurz

11 years ago

Because in serial you take 12.3 and in parallel 6.3V. Wasn't that clear?

lmccoig

11 years ago

Thanks for checking. I was trying to light heaters well and didn't check data sheet.

hurz

11 years ago

Your circuit still shows the heater in parallel@12V. In this config the voltage must not have more then 6.3V. Each heater draws 300mA for a power of about 1.9Watt. Keep it up.

Ferrograph

9 years ago

When i view this circuit the triodes don't show. Do i need to import some custom triode components?

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