XLR vs RCA

A voltage difference of 6 db (or to be more precise 6.02 db) = a voltage difference of a factor of 2 = "double" (assuming impedance remains the same).

A balanced interface will usually/more often than not provide 6 db more gain than an unbalanced interface (everything else being the same), but not always. It depends on the particular designs.

I concur with the rest of ZD's post.

Regards,
-- Al

This voltage gain is furthre reduced in power amp to achieve the same overall game. The only difference is better noise immunity.

Kijanki, in some (and I suspect many) preamps which provide both XLR and RCA outputs the signal provided to the RCA output is the same signal that is provided to one of the two signal pins on the XLR connector. And some power amps which accept both XLR and RCA inputs receive both of those inputs through the same differential receiver stage, connecting one of the two inputs to that stage to ground when the RCA input is used.

If the preamp and the power amp are designed in that manner, when an XLR interconnection is used the differential receiver stage will be provided with twice the voltage differential at its inputs compared to when an RCA interconnection is used. The output of that stage will therefore be twice as great when an XLR interconnection is used, and hence the overall gain will be 6 db greater when an XLR interconnection is used.

Best regards,
-- Al

P.S: For examples of what I described in my post just above, see the output circuit of the Bryston BP4 preamp, schematic here, and the input circuit of the Audio Research VT100 power amp, schematic near the bottom of the page here (click on the image to expand it).

Best regards,
-- Al

Al, overall gain might be 6dB higher making it uncomfortable to adjust volume. Poor design for no reason.