OK, Paul. Let’s take this imaginary 2 channel amp for example. It has this specification.

It needs a 13.8V power supply.
It outputs 500W total into 4-ohm load. (250W per channel)
It consumes a maximum current of 90 amperes.

How can I determine the type of transformer I need based on this 3 specification. (How many VAC for primary winding and how many VAC for secondary winding)

Also what about the VA? 500VA, 800VA, 1000VA, so many kinds. How to determine the value I need based on the above 3 spec.

When parallel or series those windings, should I solder them together? Or I can just tie those cable together?

The diode bridge also called rectifier, is that correct? Or are the two different things.

How much money do raw electrolytic caps usually cost? I found ready-made car caps are not cheap.

Also, what will happen if the caps UF value is really high? Like, 900,000 UF. Is that value higher the better?

Thanks, Paul. I am the beginner and need some professional guidance. Hope you have patience.