Balanced vs RCA between amp/preamp

    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.

It is. A set of Jensen ISOMAX line transformers should do the job. They make one that has RCA inputs and XLR outs.

https://www.jensen-transformers.com/home-theater/audiophile/

They make them to order too- so you can get RCA in and XLR out although you don't see that on their site.

@ 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?

In a balanced line system there is no need to lift the ground at one end of the cable. 

Try not doing it in a large multi-room facility like a sound stage, dubbing room. It may not be required with the AES-48, but until all gear is to that standard, prudence takes precedence over valor.

Most XLR gear is not transformer coupled. Not all is actually balanced.

In transformer gear, an unbalanced signal is fed through the transformer. The output can be XLR, banana, TRS, multipin, etc., etc.

While the Jensen transformers are excellent, they, like all transformers, still have a sonic signature.

Depending on the issue, adding transformers with the screen carried may not solve the problem.

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. 

If the preamp has both RCA and XLR outputs its quite rare to see a transformer used for the XLR output.

In high end audio in particular, in a situation like this the RCA is one of the phases of the XLR output (which has an inverting and non-inverting output). The problem with this approach is that ground is being used to complete the circuit, and this leaves the circuit vulnerable to ground loops. One of the goals of the balanced line system is to eliminate ground loops.

@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?