• 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.

Filaments for the Aikido

I need a linestage with a gain of about 20. This naturally suggests using a 12AY7 for the first totem of the Aikido (the 12AY7 has a mu of 40). I’ll probably use the JJ ECC99 for the second totem, to get some beefy output drive (plate impedance under 2.5k).

I want to use 300V on the power supply, which means each plate will be dropping about 150V.

I’m worried about the filaments. The 12AY7 is rated for 90V maximum cathode to filament voltage. Does this mean you can’t stack 12AY7 in SRPP or other arrangements because of the filament limitation?

My other alternative is the 6N1P (mu of 35), which is capable of higher cathode to filament potentials.