I've been using the Gemini HSR-1000 with a PCI audio card with integrated headphone amp (Asus Xonar DG) and I think i was only experiencing half the potential of these headphones before that.
I had used the headphones with a Galaxy S4, Fiio X1 and a samsung laptop. Of course, the best quality came from the Fiio and I thought that was about 100% of the max performance for these: \insert "never have I been so wrong" meme.
The volume and clarity I get from the new combo is great, I'm far from experienced in audio evaluation but what I hear is a lot more volume but completely under control, defined bass and no harsh highs or sibilance. I've listened to metal, R&B and Hip-Hop, mainly, a few symphonic albums and a couple dubstep songs i don't completely hate to see the amount of bass possible, everything has sounded better than expected. Now I kind of feel like "I need" a portable amp to use in combination with the Fiio, I'm currently convincing my wife about that, I've found it's a little easier to achieve when she can comprehend the advantages of quality audio, for that I've given to her a nice sansa clip zip and some decent iems
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