I've got about 36 hours of burn-in on my Protector, and I'm using a borrowed 3-pin full-size balanced adapter to burn it in with my HD600 using a borrowed SAA Equinox cable from Seamaster (which I will return next week once my TWag 4-pin XLR adapter arrives Monday).
I have refrained from listening to anything but the HD600 until I have given it a couple of days of burn-in with the HD600. Before I posted comments on a fresh amp with my JH13Pro, I at least wanted to give my comments using the TWag JH13Pro cable that is on its way (shipped Thursday). I am using a DACport 24/96 USB DAC/amp as a preamp to feed the Protector, and I've been listening to some 24/96 downloads of Sara K. and Nancy Bryan on my Macbook Pro.
It sounds very good, even without burn-in. The amp is pretty transparent and uncolored, and just to the warm side of neutral but not dark in any way. Bass is very strong, and highs seem crisp and detailed. The mids are very present and natural, making it good for female vocals. This is not like my Predator where I needed 350 hours to like it, and 800-1000 hours to sing it's praise. It sounds good out of the box and seems to open up quickly without a lot of burn-in. It it really continues to improve over the next 150-200 hours I will be even happier. Until then I am also refraining from comparing the sound to other portable amps.
There seems to be a lot of claims about the protector being a "desktop amp in a portable package, especially in terms of power". It certainly has more power than the DACport that is feeding it, or my D4 in 9v mode. The Protector has plenty of power for the HD600 in medium gain when driving them balanced, but I can turn it up high enough to get clipping in medium or high gain. However, those volume levels are much higher than I would be caught listening to for my pleasure. I'd guess the power levels with balanced HD600 fall above all the other portable amps that I have, but below many desktop amps like my Square Wave XL balanced desktop amp (which is down right now with bad FETs in the 12v Sigma 22 PSU, so not directly compared but going from memory).
After the Protector is burned in I will compare it to other portable and desktop amps, and post more on the power output. In particular, the 3MOVE and Vivid V1 have been my previous most powerful portables for the HD600, and the Nuforce HDP and Sq Wave XL (or ZDT and SAC KH1000) for the HD600 and HE-5. I'll have to compare the other portable amps single ended, but several of the desktop amps are balanced.
Right now I can say the Protector is a very worthwhile purchase, and likely the best portable amp that I can recommend for HD600 listening, even at this early stage (having never heard the Lisa II that others recommend).