The symptoms you described might have been a simple case of hyperacusis. Perhaps you had an ear infection at the time, or perhaps, as you suggest, using earbuds may have had some influence (I suppose ear buds are more prone to creating pressure at the eardrum during insertion and during use, for example, but I guess we'll never know, now, as it was 4.5 yrs ago).
On a different subject, I find it notable that in almost every Chord DAC thread, there is regular mention of Schitt products. To a degree, that is to be expected, since they co-exist in much the same market segment, but it is the almost rhythmic regularity of their mention that has led me to pause and ponder, on a number of occasions, this past couple of years, if there might be something more than mere chance behind the pattern. Am I the only one who has ever pondered this?