This is going to sound a bit embarrassing, but I've had these headphones for about 4 years and I still haven't been able to hook them up to a DAC or anything. I mostly just plug them into a 3.5mm port on my laptop, desktop or phone. Because of this, does anyone know of any equalization settings that might help me maximize my sound?
Honestly, you aren't missing all that much IMO. The HD558 (I'm assuming that's the one you're talking about, but this is the HD5x8 thread after all) is very easy to drive and in my experience, has sounded pretty much the same out of my various sources. I've tried it straight from my iPod Touch 5g and my MacBook Air and it didn't really sound any different from when I plugged it into my Topping D20 DAC + SMSL sApII Pro amp stack that's connected to my computer.