Zen DAC V2 broke every IEM/Headphone I have used it with.
I have had this DAC/amp for many years and have mainly used a pair of sennheiser hd599 for most of that time but have occasionally used many different sets of IEM's with them on occasion.
Almost every one of my IEM's I have used on this DAC has had the left ear bud go down to about 50% volume suddenly, not always when using it with the DAC. Once while on a plane and once with another DAC/AMP and a final time while using it with the DAC. I thought it might have just been my left ear being weird and causing preasure issues that mess with the IEMs until today when my HD599's (which I have used exclusively on the Zen DAC) has just fallen to the same fate. In the middle of playing a game and suddenly the left channel goes silent.
In all cases I have tested with another DAC/amp to confirm damage to the IEM/headphone. I now have to deal with the fact that I will have to replace hundreds of dollars worth of gear, likely with much lower quality, as I won't be able to afford to drop $500AUD on an amp and a pair of headphones.