Power supply with isolated output ...

[d@vide]

I'm a little confuse 
To have a power supply with dc isolated output (for avoiding ground loops)
I do have 1 transformer with n secondary outputs (much as the number of pedal I use like RG spyder)
or there's other tricks.
In all the power supply unit I don't think it use 1 transformer for 1 or 2 output
but eventually 1 transformer and multiple voltage regulator circuit ...
is this enough to have isolated dc outputs?
Like this....

[H.Manback]

Nope, that is not isolated. All outputs share the same ground, so when you attach a positive ground effect it goes boom (or something like that).

Also your drawing makes it seem like 317 and the like have two outputs, but in reality they only have one output. The output it gives is relative to the ground of the power supply attached to it, so all your ground symbols on the right are in fact the same ground point.

[d@vide]

...then isolated dc out only with separated secondary transormer out .... right?

[H.Manback]

Exactly (or of course a complete seperate transformer, whichever you can find easiest)