My D5 drives a pair of HiFiMan HE400i's, the 2015 version. Comparing the key specs:
| Impedance | Sensitivity | FR |
HE400i (v2015) | 35Ω | 93dB | 20Hz-35KHz |
Edition XS | 18Ω | 92dB | 8Hz-50kHz |
From my experience I can just
barely drive my HE400i's to full volume (for my ears at least) when using PEQ via the 1/4 headphone jack. If I really want ear-splitting levels I have to switch over to the XLR headphone out.
That said I don't know much about headphone specs, so I don't know if your Edition XS's -- because of the differences in impedance and sensitivity -- are somehow that much harder to drive than a pair of HE400i's. Or if the power required to drive these two is not that much different, then is there potentially an issue with your D5, your power source, your XLR cable, etc?
Obviously some of the best headphone amps that Amir has reviewed deliver significantly more power than the D5; it's not a standout amp in that regard. The
Monoprice THX 887, for example, can drive 3.7 watts (50 Ohm load via XLR, on High gain). That's almost triple what the D5 can do for a 50 Ohm load via XLR.
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