Hi Alvin, good to hear from you
Yep, I guess 5.5V is "acceptable" but I use a $3K DAC and I would really hate frying its USB board due to overvoltage....I believe it was supposedly burned-in when I got it, its previous owner had let it run for weeks IIRC?
And I rest my case that a +5% voltage drop under load on a $400 PSU is not acceptable, discrete is so much better huh. Its oxidizing 2 pins connector that you are advised to unplug & replug a few times every few months was the icing on the cake for me, so much for "plug & forget".
Anyway, there is no question that a short Injector cable sounded far more balanced to my ears on the DP1 than the stock cable Pardo provides. This said, we all use different gear and have different tastes, the beauty of used equipment is that I sold it to you at no loss and you could do the same so no harm done as there's really only one way to find out how something will sound within our own home environment. Surely any USB PSU's performance will also change depending on the voltage regulator(linear/switched mode) your audio equipment uses.
You are running a LCD-2 rev1 IIRC that would supposedly be quite dark so I guess you might have some use for a bright sounding PSU?
BTW, I've found a very short A/B USB cable that would prolly do wonders instead of an A/B adapter, more on this ASAP.