Balanced vs RCA between amp/preamp

@atmasphere 

"  You don't need transformers, but without them supporting thebalanced starndard get a lot trickier. We devolopd a means that is direct-coupled and yet floats the same way that a transformer winding does"

     I want to know the detail of your means. Could you please explain. Thanks!

@ atmasphere

           Are you talking the connection between RCA preamplifier and XLR power amplifier ? or the circuit inside the amplifier?

          I just want to have a solution between RCA pre and XLR power amp, it seems the transformer coupled is the simple way to go.

@ atmasphere

        Thanks! I put the order a few days ago and will receive very soon.

So finally it goes down to the transformer isolation,it seems the usual way even the XLR output from the pre,they usually get the rca signal first and use the transformer to get the inverse signal and consist the XLR sigjnal. 

Am I right?

@atmasphere 

" The problem with this approach" Do you mean Transformer coupled approach?

As far as I know transformer coupled way is to solve the ground loop.

That's the reason we use the transformer isolation instead of RCA to XLR cable,right?

@atmasphere 

 You suggest to use transformer isolation and you deny the way to use it. 

What is your opinion?

Audio Research reply directly that I should use transformer coupled  to connect RCA pre with their XLR only power amplifier.

So that's it. I will feedback when I receive and install the transformer in my system.

I tried the direct  RCA to xlr cable before, and I can hear the soundstage is not good.

Just connect the ISO MAX transformer in between my RCA pre and XLR power amp,The sound is changed too. It is not very  active as it before and Sound volume is not gain +6db,but become a little small.  Totally different sound. I just remove it from connection. No good for thus isolation transformer.

Rega Cursa 3 pre and  audio Research VT100 Mk III ( this model has rca input and I just do the test and if ok will move to Audio Research Ref 75se.)