SOT: Stepping down from high voltage (tube amp)

[brett]

Hi.
I've seen some cheap power transformers on e-bay etc., but my problem is that they usually they don't closely match the voltage requirements of the circuits that I'd like to build.  For example, I'm thinking of building the November (at AX84.com) that requires 380V CT.  There's a cheap ($10) transformer on e-bay, but it puts out 440V CT.  How can I knock the 440V down to 380V at reasonable cost??

(I assume that a voltage divider is out of the question, given the current required.)

many thanks for any help

[Peter Snowberg]

You're very correct about the voltage divider approach not giving enough current.

The standard way to drop a bunch of volts in a tube amp is to use a Zener diode in series with the ground lead for the HV transformer winding.

By adding it to the ground, you can use large "stud" mounted zeners which are required for dealing with the current.

Sorry I don't have part numbers or values.... but stud mounted Zeners are what you probably want here.

[brett]

Thanks Peter
yeah....makes sense....
Now that I know what to look for, I'll search the web

cheers

[Regan]

Its late and I'm tired, so I may be having a brain fart here, but 440v center tapped means 220v-0-220v, right?your looking at just over 300v out of that transformer if I'm not dilirious.
Regan