Transformer wiring questions for TDA1514A chip amp

[doug0147]

I started this discussion in another thread, but I think this might deserve it's own thread.

I am building my first (real) amp (other than the little gem or ruby) based on the TDA1514A chip.

I'm using this schematic - http://www.electro-dan.co.uk/electronics/tda1514.html

My problem is that I've not built anything that requires more than a 9V battery or wall wort. The 25+/- power supply is new to me. In the article on that link he has a schematic for a power supply. He says I will need an 18-0-18 transformer. I'm new to this stuff and I want to make sure I find the right transformer. Where can I find a transformer like this? Can anyone post a link? How is the transformer wired to the circuit in his article? If it is an 18V transformer does the circuit turn it into 25V? Or does the transformer put out 25V? I know these might be dumb questions, but I have to ask.

Thank you for your help!