Originally Posted by Balisarda
Regarding the NAD C 390DD direct-digital amplifier, has anyone compared the sound quality of its XLR and RCA digital inputs? All first-hand experience is welcome, but I'd prefer hearing from those who have used the same source component, i.e., one with both XLR and RCA outputs.
Looking at the doc http://nadelectronics.com/download.php?120810144609-NAD_C_390DD-DataSheet.pdf|DataSheet%20-%20C%20390DD%20Direct%20Digital%20Powered%20DAC%20Amplifier
We can see that the XLR digital input is for AES/EBU while the RCA inputs are SP/DIF.
Not unexpectedly they accept the same sample rates and data formats, which is no surprise to informed parties since devices with both of these inputs implement them as different input coupling circuits to the identical same signal processing including the line receiver. I've done extensive technical testing of a number of other devices that had both kinds of inputs, and there were no signficiant differences in technical performance or sound quality.
However, I can pretty much guarantee that they will sound different in a sighted evaluation! ;-)
There's only one way that these inputs could possibly actually sound different and that is if the NAD C 390DD was a total and unmitigated POS.
I suspect that the 390DD is a quality piece.
In most cases SPDIF and AES/EBU inputs can be used interchangeably with the same source of either kind with a simple adapter, electrical differences notwithstanding.