EPAll, that's assuming exact perfect input values with no allowance for what Ian describes. I've no doubt I am probably over the limit, in terms of my input voltage being a bit high. I'd have been happier with 20.00 Volts or there abouts, with no more than a 3 Volt drop in voltage at 10 Amps. I think although not certain, the transformer will drop about 2 to 4 Volts going by the 300VA transformer I have recently used for another PSU. Same manufacturer just 12.00 Volts, I want know the exact drop underload until I test it. I still think it's going to be a bit to high really. Having used a few of these Vigatronix toroidal transformers, they seem very efficient. And I can't see from a previous post, where a buck converter would be useful, it would turn a linear power supply in to a hybrid linear plus switching power supply. I think the most practical way is to remove secondary windings, but I don't know how well that would end up. Diodes and the numbers of them needed would border on stupid. The power resistor sounds a good idea, but its probably got to be a bit of a beefy aluminium clad type resistor. Then I still have to work out the voltage drop, then calculate the value and power rating of a resistor that's suitable. Although that idea is still wasteful of power. These transformers where £42 each, I'm trying to find a way to using it with out ruining it. Ideally I would have gone for a 300VA transformer with 15.00 Volts secondarys, but there where non available at that power rating at that time.