6418 valve booster/drive/preamp PSU help!

[PaulBass]

I found a better schematic from another engineer



R1 - 1MΩ, sets the input impedance
R2 - 18Ω, limits the current on the cathode/filament
R3 - 100KΩ, the load resistor,
R4 - 6.8KΩ, the upper half of the voltage divider for the 1.5vDC
R5 - 1KΩ, the lower half of the voltage divider
R6 - 1500Ω at 1 watt, drops the incoming voltage down to where the zener can work with it
C1 - 10µf electrolytic, bypasses the cathode's AC to ground
C2 - 1 - 10nf, optional, used mainly to suppress RF transients that might become audible
C3 - 10µf electrolytic (can be polarized or non-polarized), keeps all of our DC inside our own rig
C4 - 10µf electrolytic, smooths any small fluctuations found on the incoming phantom power voltage
D1 - zener diode, select to provide the desired voltage

an input cap isn't needed but you can add one. I prefer to have one. I used a 10uF metal film cap for C3 instead of the electrolytic.
R4 & R5 is the voltage divider for pin 5 to give it 1.5v. The divider eliminates the need for the 1.5v battery
If you use a different supply voltage you'll have to adjust R5, I used a trimpot

[PaulBass]

I forgot to mention I bought the tubes here, only $1.99 http://www.piexx.com/index.php?main_page=product_info&cPath=10&products_id=33 Glad I bought extra because I knew I was going to fry a filament, and I did.  If you are using the voltage divider setup and use the wrong resistor the filament will pop. doesn't take much, only 3V will fry it