But is that also saying that the Fireface is doing a good job of reproduction in the first place, so that you can hear the loss, versus something like an M-Audio where your playback of recordings of digital from the Axe FX is identically washed out when compared to analog from it?
I seriously don't understand the question...
I will try to answer it:
The whole Analog/digital conversion thing is very complex to explain. But YES, RME Fireface 400 is very good to reveal if something sounds like bad sound quality recordings. But RME fireface 400 is also very good to record the analog signal with very little loss of detail or quality.
When you record the SPDIF signal from Axe FX, it has already been converted from analog to digital using the AXE FX converters! So the sound you hear in the monitors is more "pure"
But then it depends what soundcard you are using! If you use a expensive stuff like Apogee or RME, it will sound better, but if you use something cheap it will not sound so detailed.
You must understand that you can record SPDIF using a cheap soundcard and have good quality recordings, because the signal has already been converted in the Axe FX, it goes directly to the hard drive as a wav file. But when you listen to it, it will sound bad, but that is only because of the low quality converters inside the cheap soundcard. If you used a better soundcard it will display the sound more detailed. So now you have a situation where the recording is good, but when you listen to it, it's missing the "sparkle"
Wow, When I read this, I can hardly understand it myself.
Sound conversion is very complex to explain, but in the end you can use the Axe FX 2 as your soundcard, it sounds awesome!
I just use my RME fireface to mix songs.