Originally Posted by daseinpdx
I don't know what the other guy is talking about. Even the AK100 can drive the 400s (35 ohm impedance and 92.5 db sensitivity) and its amp is much less powerful than that of the dx50. The amp on the DX50 is more powerful than the typical DAP. So, yes, you can listen to the 400s on the DX50 without an amp. On the other hand, they will definitely sound better with a decent amp. The DX50 has a relatively powerful amp, but it wouldn't be as good as most decent external headphone amps. Of course, it would sound much better with an even better DAP too.
Originally Posted by sragoowanshi
Dx50 & he-400: It seems that I need to try it out for myself then. If an amp is necessary, I'll pick one up later? Any cheap/budget suggestions?
Power does not equate to volume, yes you can plug in HE-400 to DX50 directly and it may play loud enough but the sound will be distorted or clipped on many cases.
The HO on DX50 sound distorted at high gain/max volume using my Beyer T1 which is much more efficient than HE-400 at 102 dB/mW.
As a guide, someone has measured the max power output of DX50 at 1% THD without distortion/clipping.
For HE-400, you would at least want an amp to "properly" drive it to around 115 dB especially if you are listening to classical music, and it will require around 180 mW of power. For pop and rock music and if you are satisfied listening at moderate to low volume (105 - 110 dB) HE-400 needs around 60 mW. At high gain, you also raise the noise floor on DX50.
If you are ok with that level then it's fine, but it will certainly sounds better with a powerful external amp.