• WARNING: Tube/Valve amplifiers use potentially LETHAL HIGH VOLTAGES.
    Building, troubleshooting and testing of these amplifiers should only be
    performed by someone who is thoroughly familiar with
    the safety precautions around high voltages.

Akita 12V preamp thoughts

The heaters are depicted on the schematic below as four 74 ohm resistors in series with a 68 ohm dropping resistor. Simulation shows 2 watts being dissipated in the 68 ohm resistor.

With the 18vac version, there is a 10 ohm resistor and barely enough voltage on the 12.6v heaters.

As far as the aikido circuit itself, you will want to change cathode resistors to shift the operating points.


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Filament voltage derived from the spot I marked "X" and the negative voltage probe (black colored) shown below with ripple expected. 68 ohms drops it to about 48vac across the 4 series filaments with even less ripple due to the RC filter of R11 and C10.http://www.tubecad.com/2013/03/blog0258.htm

For an in-depth review from the designer himself of this sextupler circuit, refer to his blog:


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Anyone know which tube/voltage option would play better with a Gainclone amp? 6DJ8's provide a gain of 15db, 12AU7's a gain of 9db. I believe the Gainclone chips all run at a minimum gain of 10db?

I was thinking about 6DJ8's @ 15db and a LM3886 @ 15db for a total of 30db. Too much for an 'integrated'? Am I missing something about how these would interact?

Tubecad 12VAC article if everyone hasn't already found it.