Going by past experience with that design I would put in the 1 - 1.5 KVA range.

U mean the second picture transformer or the Yamaha one in post #37

Sorry ! the Big one it is.
So how are you figuring this. The core size and wire gauge ?

 

Post #1 'U' core transformer.

Estimated size Vs similar transformers I have worked with in the past.

What did it come out of?

 

An amplifier
2 tx in one

I have posted the core size

 

and what was the amplifiers input power ratings?

 

That is not clear. The guy who gave me cannot tell.

 

When winding the secondary you calculate the secondary volts/turn and from tht you wind what ever turns u need.

Does the volts/turn apply to any wire size. I mean can I measure with a single strand insulated wire and calculate the turns needed then wind the original wire ?

Does the rule apply for innermost and outermost windings?
The outer layer is much lengthier wire you know.

 

In practice, the ratio works out to the same for 1st winding and any other.
Any gauge will do, I usually put on ~10t at least to get a fairly accurate result.
Max.

 

Does the same goes for toroids ?

 

Same principles.
Toroids more efficient.
Max.