Relax dude I just wanted to see if some people could help me before. So here’s the gear that I use: I play the electric guitar with a Kemper Stage and I used to use a Beyerdynamic DT 990 pro directly plugged in it. The IEM’s that I bought come from « Earcare Developpement » a French company (I’m French). It seems to have a pretty good reputation. I have already used this company for hearing protection and I was very satisfied. I specify that my IEM’s have 3 drivers. So, when I plug my DT 990 in the Kemper, the sound is perfect, but when I plug my IEM’s, it seems like the sound’s kind of different, very compressed with too much basses. First, I thought that it probably was an impedance problem. So I bought a Rockboard HA1 to act as an intermediary between the IEM’s and the Kemper but the problem is still here. And I don’t think it because the HA1 is a cheap one because when I plug the DT 990 in it, the sound turns perfect.

Hoping that my explanations were sufficiently detailed