# Transformer for electrostatic speaker (high voltage, very low current)

I've read recently about DIY projects making electrostatic loudspeakers (example). The membrane of the speaker should be supplied with bias DC voltage between 1 and 5 kV, roughly. There is virtually no current needed, only for charging the membrane.

With old CRT screens and photocopiers being short supply, how does one get such a voltage? Around here, only step-down transformers are easily bought, and I don't really want to be using any of those the other way around (effectively putting the rated voltage on the secondary coil).

I can imagine getting nearly 1 kV directly using a 1:1 transformer and voltage quadrupler, but this may prove inadquate. So the question is whether there is another way to get high DC voltage when I can't get my hands on an up-to-spec transformer.

Europe here, so 240V on the tap.

So the question is whether there is another way to get high DC voltage when I can't get my hands on an up-to-spec transformer.

There is no option, you need to pass high voltage audio to the plates and this can only done using a transformer: -

The picture above shows your power amp (to the right) feeding the LV side of a step up transformer. The turns ratio is $\sqrt{\dfrac{20k}{8}}$ = 50:1 stepping up.

The DC bias supply feeds the centre tap of the HV secondary and to create that bias supply requires one of these: -

or maybe even one of these: -

Cutting thru and getting to the point, if you did not realize that you are likely to electrocute yourself - yes I know that's a generalism but this thing can kill you.

There is nothing wrong with diode pumps for making KV .Low currents and high frequencies mean small ceremic caps Diode pumps work well on Boost convertors with the S TRAP switching loss reduction scheme .Also diode pumps work well on the self oscillating tuned collector pushpull invertor that is seen in LCD backlighting.I havent done this but I think that a camera photoflash invertor could drive a diode pump turning hundreds of volts into KV.Remember that there isnt really an upper limit .You dont need to stop on the quadrupler ,I once did a OCTUPLER.