A HV linear amp transformer is very expensive. Peter Dahl transformers start around $350. Even a used Heathkit SB-220 that is only a 1KW input transformer sells for around $200 used. Transformers that are more reasonable in cost are Antek Transformers in NJ. The Antek AS-AT800 is 850 volts output and costs $105. It is rated at 960va on 60Hz power. Using a voltage doubler it produces about 2100-2200 volts under load and is excellent for a pair of 572B tubes. Placing the two windings in series makes about same voltage using a bridge rectifier. Transformer includes two 6.3 volt windings with enough current to operate a pair of 572B tube filaments. Another transformer is the AS-AT950 that is about 2000va rated on 60Hz power. It will produce about 2500-2600 volts using a voltage doubler or bridge rectifier with the two windings in series and will support a 1500 watts PEP output amplifier with a pair of 3-500Z or high power ceramic tube such as a 3CX1500. Transformer includes two 6.3 volt windings to produce 12 volts DC for accessories or can operate a 3cx1500 filament with a voltage dropping resistor from 6.3 volts to 5 volts.. It costs $195. Unless you can find a surplus transformer or a bargain from another Hams parts box, this is your best deal. Note- the transformers are rated on 115 or 230 volts input thus the output voltage is a little higher on the standard 120 or 240 volts input. The transformer are hi-pot tested above 3.5KV.