I'd be interested in the "Normal" listening level you have the MDAC set too - if its less then 30dB then maybe attenuators should be use...
Try driving them directly from the MDAC... even maybe with XLR balanced... but the MDAC current limit will kick in around +/- 120mA... not sure how loud this would be in real life with 97dB speakers...
John
Just a quick report back as promised about the 'normal' listening levels on the system while driving the power amp with the MDAC directly, during my weekend dem- about the maximum level I ever had set was -28dB listening to certain classical tracks quite loudly. Most rock/pop had to be turned down considerably lower at about -40dB or so and was still fairly loud.
In any case, I found that in my system this didn't produce desirable results, the sound lost it's 'substance' quite dramatically, so I went back to using the preamp which improved things greatly. Ultimately though, for all the things the MDAC got right, and there were many, it's not the sound for me, but was a fascinating listen in terms of my first experience with computer->DAC audio. I'm sure this is the way of the future, although maybe with a solution which simply places an HDD or SSD inside the player (a CD player with a hard-drive instead of an optical drive, if you will, like the Naim HDX or Meridian MC200). Sound quality aside, I found the whole experience of fiddling about with computer settings, network cards, yada yada, very dull- after a couple of days I longed just to open an album and pop the CD in the drive!
The other thing I tried was one of the Olimex isolators, which did make a difference, but sadly for the worse- everything became flattened and with a tooth-grinding glare to it. Anyone want to buy mine?!
I'd be fascinated to try an MDAC with the PSU mods John is working on, and a more accurate clock locked dedicated transport, again with proper attention paid to PSUs, jitter, etc., to see how things improve, though, and wish you every success with its ongoing development!