[Tadis]

Or the headphone output on the monitors has a high output impedance that boosts the midrange, or that's its distortion pattern, while by contrast the Schiit Magni isn't coloring the sound.

If Schiit wasn't colouring the sound then the vocals should sound good. But it sounds awful. I don't know anything about the technicalities involved in sound etc. so it's hard for me to describe. But it sounds as if someone edited out some frequencies. The vocals almost sounds monotone. It's like all sighs and rasps that you hear in a good vocal are gone. Even when the headphone are connected to the back of my PC the vocals are nice and rich but if I connect them through the Schiit it all goes flat... The only improvement with the Schiit setup is more powerful volume. I don't know if the DAC or the Amp is to blame. Can't connect the headphones directly to the DAC to test it out.

 

[ProtegeManiac]

If Schiit wasn't colouring the sound then the vocals should sound good. But it sounds awful. I don't know anything about the technicalities involved in sound etc. so it's hard for me to describe. But it sounds as if someone edited out some frequencies. The vocals almost sounds monotone. It's like all sighs and rasps that you hear in a good vocal are gone. Even when the headphone are connected to the back of my PC the vocals are nice and rich but if I connect them through the Schiit it all goes flat... The only improvement with the Schiit setup is more powerful volume. I don't know if the DAC or the Amp is to blame. Can't connect the headphones directly to the DAC to test it out.

That's exactly my point...maybe that's exactly what the DT990s sound like (ie, awful) and the Schiit amp is showing it exactly as it is. By contrast everything else you've plugged it into could have a high output impedance. On low impedance headphones the effect will either trim or boost bass; on high impedance headphones the effect can sometimes be a midrange boost, which then helps you hear more of the details in the midrange amid the boosted lows and highs.
https://diyaudioheaven.files.wordpress.com/2013/03/dt990-250-fr.png

 

[Tadis]

That's exactly my point...maybe that's exactly what the DT990s sound like (ie, awful) and the Schiit amp is showing it exactly as it is. By contrast everything else you've plugged it into could have a high output impedance. On low impedance headphones the effect will either trim or boost bass; on high impedance headphones the effect can sometimes be a midrange boost, which then helps you hear more of the details in the midrange amid the boosted lows and highs.
https://diyaudioheaven.files.wordpress.com/2013/03/dt990-250-fr.png

I see what you mean. Either way that's pretty screwed up. Whether it's the £110 headphones or the £250 dac/amp. And I have no way to test which is to blame without spending £££. For now I'll just stick to using those headphones by connecting them to the monitors. It bugs me a bit that I can't get nice powerful volume but like I said the sound quality is good and I mostly use them at night when lots of sound is not needed anyway.