SoZ power supply

I would like to build a 10 watt SoZ, and suggestions to build the PSU are welcome.

1) Is a 450 VA transformer with 18 V secondaries appropriate for one channel (or 900 VA for both)?

2) How big the caps should be? For example 4 high ripple/low esr caps of 10,000 uF are enough?

3) I am going to wind my own air core inductors because I am not able to find anything capable to carry 3 amps. Any suggestion for the shape (e.g. a solenoid) or for the copper wire gauge?
 
18V 2ndaries won't get you 10 watts. After rectification you might get 5 watts output. 400VA with 18V 2ndaries is perfect. But if you want 10 watts output, you need a much higher voltage transformer.

I find the graph shouldn't be strictly read to get a VA rating for the transformer. The speaker load is dynamic so at times when the SoZ sees a 4 ohm load - the wattage can double down and therfore, the draw of the power supply will want to double down. So I normally choose a figure TWICE of what is shown in the graph.
 
cjunk said:
[/B]What about a 500 VA / 25 V sec. transformer? [/B]

That should be fine so long as the house wiring doesnt load down too much or the local substation doesnt supply flaky power ....... either of these could cause that 25V to drop substantially in which case it would not give 10W output. if this is the case, 2 x 30V secondaries should provide enough head room.