I want to build a HV DC power supply for a tube amp ( 1.2 kV at about 500 mA). I intend to make it light using multiple voltage multiplier stages and no transformer... Having no transformer I am facing the following problem. If I use a schematic like this one: voltage multiplier

And I consider the case of the power supply to be the ground it is very important how I connect the plug and which wire is the phase and witch one is the neutral because I could end up with the phase connected to the case.

Another method could be using a pair of Switching Relays that work at 220 V and automatically connect the phase and neutral to the desired position and create something similar with this schematic:


The problem with the second approach is that using modern household circuit breakers (like RCCB circuit breaker), the solution does not work.

Can you please advise me how to do this?

  • \$\begingroup\$ did you you mean nul to neutral? \$\endgroup\$ Oct 18, 2012 at 10:22

2 Answers 2


Get a proper transformer.

1.2KV at 500 mA is a substantial amount of energy and you will likely pay a substantial amount of the price of the transformer in the price of components trying to build a suitable voltage multiplier. Multipliers also work far more effectively when driven from a square wave than when used with a sine wave source and this will put substantial requirements on the multiplier components that raise their cost even more.

The transformer also adds the level of safety isolation that is needed to make things safe. The value of the safety has no comparison toward the cost of the suitable transformer.

  • 1
    \$\begingroup\$ If you are in North America, discarded (free) microwave ovens are readily available with transformers typically having a secondary voltage of a couple of KV at 0.5 to 1.5 KW. You could lower this voltage in some way, including removing about half of the secondary. With the voltage you mention, I assume this is for a transmitter. "Tube Amp" with no other qualifiers usually means "Guitar Amp" to most people these days. \$\endgroup\$ Oct 19, 2012 at 3:04
  • \$\begingroup\$ +1 for "get a proper transformer". Or, implement a good SMPS, but that is a lot-lot-lot trickier than getting a good transformer. Without proper isolation, you - or somebody who you like - will die! \$\endgroup\$
    – ppeterka
    Oct 20, 2012 at 19:52

enter image description here

T1 is an ordinary 9V 1A transformer connected backwards for step up. Additional circuit details and a parts list can be found here.

  • \$\begingroup\$ be wary of using step-down transformers in reverse. the insulation in the windings may not be rated for the resulting increased voltage. \$\endgroup\$
    – JustJeff
    Oct 20, 2012 at 22:16
  • \$\begingroup\$ @JustJeff Good to know! Any guidelines on what may be safe and what definitely isn't? \$\endgroup\$
    – rdivilbiss
    Oct 22, 2012 at 0:31

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