Just got the unit and hooked it up. RPA-2 has the XLR and RCA both active and alive at the same time without any hardware switching necessary so made this comparison very easy to do. I have the ERC-1 connected to LMC-1 7.1 channel inputs to bypass the processing and then onto the RPA-2 via the RCAs. I connected the XDA-1 directly to the amp via the XLRs, used the coax connection from the ERC-1 to connect to the XDA-1. Both RCA and XLR connections were done at the same time.
These two output pathways sound quite different! XDA-1 was more crisp and lighter, while ERC-1 was heavy and sounded denser. I was able to switch back and forth by muting one device or the other and playing them so that the volumes matched.
Obviously, more listening needs to be done to be conclusive, but the difference in timber I heard was quite noticeable using this approach.... ERC-1 == heavier and denser sounding, XDA-1 == lighter and more open, crisp sounding.
I've think I asked before if anyone knew which of the two inputs (XLR or RCA) on the RPA is more 'direct.' For example, the XPA-1 is balanced. An op-amp is used on the RCA (unbalanced) while the XLR (balanced) is straight in. I don't think anyone knew, regardless there could be a very subtle difference in sound between XLR and RCA.
Also Audioholics found with the RPA that the gain of the XLR is about 1db less than RCA. It's tiny, but that could be enough for that difference you're hearing. If you have a multimeter and a play a tone or white noise, you can measure the AC voltage from the speaker output to find a matching volume level between XLR and RCA.
Looking forward to hearing more of your impressions though.
mmm... if an opamp is used to convert the balanced input signal to unbalanced in the RPA-2, then the RCA would be more "pure" input path ? Then unless one has an XPA-1, the XLR connection into any of the non-balanced amps would kind of defeat the purpose of maintaining the signal purity... interesting idea. Does anyone know this for sure?
The sound difference between the ERC-1 (RCA) and XDA-1 (XLR) is quite a bit on my system so much so that I can definitely tell that it is more open and crisp sounding coming from the XDA-1. I will now try the RCA input on the RPA, connect this to RCA outs from the XDA to see what happens.
Well, I tested running the RCA from the XDA-1 vs. the XLR from the XDA-1 to the RPA-2 amp. There is a subtle difference between these two connection modes in that RCA appears to give **slightly** more forward presentation and dynamics than XLR, which could just be the dB sensitivity difference, actually, that's probably it.
What I heard between the ERC-1 versus XDA-1 difference definitely is not because of this, at all, period. The timber is different, ERC-1 is more dense, darker and solid sounding, but XDA-1 is more open and wide/expansive and crisp. May be the dense and darker sound comes from the slight compression effect from the lesser output stages, who knows, but the difference is there. XDA-1, if anything, is more engaging than ERC-1, much like what I noticed going from LMC-1 DAC/output stages to ERC-1 direct (or USP-1 while I had it) not so long ago. That took some getting used to back then. Now, this is also having a similar effect. These two output stages are different in tonality and expansiveness that my ears are having to readjust again...
Overall, I think this will be a great addition to my system, especially running all of my other digital gear through including the good old DAT deck. Happy so far.
I think you make a good point regarding the XDA-1 being more "engaging". I described the same thing as it being more "intimate". It's just draws you into the music more with it's smooth and detailed sound. Definitely happy with it here too!