Hello RME and RME users,

be warned, i'm french so my english... usually sucks

i've been using (and promoting) RME (products) Fireface 400 for more than 10 years and i never faced such problem.
Yesterday i had to record classic guitar and used two static mics with +48v on. I had a not-so-light buzz (nearly all frequencies but mainly audible on high-mid spectrum) in both mics' takes, not audible within the direct phone monitoring (while playing live), but inside the WAV recorded (24bit, 44.1kHz) when playbacking. I tried many things but the only solution seemed to be taking off one of the 48v... !!?!
It's quite strange 'cause i didn't change anything in my system. i have a very powerful platinium power supply in my PC and firewire connection never failed since.
Any tips or ideas ?
I'm gonna try self-powering the fireface with its own supply for troubleshooting. and try to make my urgent takes with 1 static+1dynamic mics instead.

Thank you for any investigation help.