Special thanks to Calvin at the DIY Audio Forum for sharing his experience using inexpensive 230v/6v power toroids in ESL's. They sound fantastic at about one-tenth the price of the specialized ESL toroids from Plitron or Aplimo.
Polarity Warning:
Cheap toroidal power transformers work great for ESL's but you can't always trust their winding polarities will match the phasing dots on their data sheets or my schematics.
One of the VTX transformers I tested had its red/black leads reversed, such that one 6v winding was out of phase. So when I assembled the transformer pair their windings cancelled and I got no sound. Once I figured out the phasing error and reversed the leads, they worked fine and sounded wonderful.
Winding polarities can be checked with a DVM and jumper wire by applying 115VAC to the primary and measuring the voltages out of the secondaries, as shown here: Transformer Polarity Test
Update 5/21/14:
At this time the only source I know of for single primary 230v transformers that will accept a US credit card and ship to the US are these 230V/2x6V toroids at Rapid Online. I have tested them and they sound great.
Electronics Package:
Below are my simple bias supply with tandem VTX 50VA 230v/2x6v transformers.
