Originally Posted by Marleybob217
Thanks for the advice! I noticed the O2 amp has an output impedance of 0.5, so this should, atleast in theory, sound quite a bit better with the HE-400 than the E9.
Then again, My gmp 8.35D has an impedance of 35 ohm, but it sounds really nice through the E9.
If I understand you correctly, than something with a high output impedance like the traktor audio 2 (100 ohm indeed) should sound worse with headphone that have low impedance.
However this dac is meant for typical DJ headphones that have a relatively low impedance. And the traktor audio 2 did sound much better with low impedance headphones than the HD650.
So it can't be just the rule of 8 applying negatively.
Originally Posted by preproman
What - the HE400 does? No way...
Innerfidelity claims the HD650 needs 0.13mW to reach 90 dB.
They also claim the HE-400 needs 0.33mW to reach 90 dB. So, mW to mW, you need about 2.5 times the power to drive the HE-400's to an equivalent level as the HD 650. Hence my assertion.
Its not that the power requirement of the HE-400 forces you to have a massive amp - it doesn't. For the sake of having adequate volume and
headroom however, I think 0.5-1W is necessary.
MarleyBob - I can vouch for the O2 - it kicks butt and has plenty of juice for the HE-400, and virtually anything else you throw at it. The Traktor audio 2 you refer to, according to their website, is rated to drive headphones from 8-600 Ohms, and produce 100 mWs @100 Ohms. Given that, generally speaking, power would double at half that impedance, it should do something like 200 mWs @50 Ohms, and 400 mWs @ 25 Ohms. It depends on the design of the amp, but this suggests to me that output impedance is actually low! So that would explain why it seems to work well with lower impedance phones. But again I am no expert, and without more information about the amp, its hard to know if it should or shouldn't sound great with a variety of phones. But it certainly would have enough power to get loud with HE-400s.
That said, I recommend the O2