Firewire - Thunderbolt - EDIROL FA101 issue

I just received my brand new custom ordered iMac, but it has only thunderbolt ports. My whole home studio system is based on my EDIROL FA101 Firewire audio interface that worked like a charm through the Firewire port on the older iMac. Now I had to buy an apple made Thunderbolt to Firewire adapter to conncet the EDIROL.

Now its bad... Everything is the same setup, as I use it for years, and it has nothing to do with drivers or Mavericks since the old computer I used until last week had Mavericks too. Now the music stops for seconds frequently in every player, iTunes, VLC, Youtube even Logic pro. Just stops for a sec, than continues and stops again and keeps doing this. (Just to make sure, I returned the Firewire - Thunderbolt adapter to the apple store and they gave me an other one, just to make sure that is not a corrupt adapter)

I have tried everything. First I have switched to BUS mod on the back of the EDIROL menas getting the power from the computer, cause I thought the power coming from the EDIROLs AC adapter and the Thunderbolt adapter is having some conflict but nothing changed, or I've got even more stops and some noise too. Than I pluged AC back on the EDIROL, so thunderbolt is getting it's power from the iMac, EDIROL from the wall, but I still have the issue. Stops, often, than not often. Sometimes I have 10 stops within a minute bot sometimes plays the song correctly... I need some help or advice.

Thank you guys!