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12ax7 power requirements

:

12/1/2004 12:56 PM

12ax7 power requirements

Ruetz and the real Mc tube guy have these preamp power supply ideas involving common "wall wart" plugs you can find anywhere.
Ruetz goes on to say:

"The step-down PT needs to provide enough current to supply however many 12AX7s you plan to use, plus at least 100mA extra to feed the step-up PT."

Well, how much current would 4 12ax7s need?

I am trying to build a preamp test powersupply.

The rest of Ruetz's article is here:
http://www.diyguitaramp.com/preampps.html

Thanks

12/1/2004 10:35 PM

If you're making a piece of test equipment,
you want to be confident that it doesn't
affect the equipment under test in a
non-optimal way. So if you want to minimally
power 4 12ax7's, you'd need 4 * 150mA @ 12.6V.

What if you want to run the heaters at 6.3V ?
Or have more than 4 tubes to heat ?
Or a pre-amp that uses some other tube ?
Or want to 'float' a tube or two at some
elevated heater voltage ?

That's when it's handy to have plenty of
watts/other circuitry available.

If, however, 4 tubes is the absolute maximum
number of tubes you will need to heat, then
600mA is enough.

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