Originally Posted by PurpleAngel
Run optical cable from Mac computer to Onkyo receiver, plug whatever headphones you get directly into the Onkyo's headphone jack.
Philips Fidelio not recommended as they have a low impedance (Ohm), and receiver's headphone jacks usually have high impedance headphones jack, but I believe the HE-400s are not really negatively affected by high impedance headphone jacks.
I think this would be a good idea, at least initially. Most receivers can drive headphones at close to the same quality as an entry-level solid state amp. This way, you can hear what they sound like and base your amp decision off of what you're hearing instead of just what you're reading. You might find that they are more or less bright than what you're expecting, and then you can adjust your DAC/amp quest accordingly.
Both the Magni/Modi and the ODAC/O2 probably aren't going to reduce brightness at all, but this isn't necessarily a problem if you're willing to EQ. The HE-400 responds to EQ very well, so the main advantage of using a DAC/amp is going to be in terms of detail and soundstage.
I have an average Sony receiver from the 90's that can drive the HE-400 competently, but it's missing those last few layers of detail, clarity, and air compared to my dedicated headphone amp. Bass/mids/highs balance is more flexible when EQ is in the equation.
Edited by manbear - 10/6/13 at 9:30pm
I'd suggest also looking at Audio-GD.for a DAC. Most of their products are reputed to be a bit more on the warm side of neutral (as far as solid state goes) than Magni/Modi/ODAC/O2. They make several DAC/amp combo units that have a lot of power and get good reviews as well. I'm thinking about getting one of their Compass models for my next DAC so I can have a chance to try a nice solid state amp too.
If you want to go tubes, there are a lot of choices out there. A Little Dot Mk 1 might be a good place to start -- it is a hybrid amp that can deliver a lot of current, which is what planars like. Power isn't just a matter of volume. I have the MK3 (which I really like), but I've read that it's not ideal for planars due to being an OTL design. I had it before I got the HE-400, so whatever, I'm content for the time being, but it's probably not the best choice if you're trying to build around the HE-400.
My first and only dedicated DAC is the HRT Music Streamer 2. I'm very happy with it, and it's supposedly on the warm side based on what people say (I have no reference for comparison other than my stock soundcard), so you might want to check that one out too. But the design is relatively old compared to the many other low-cost DACs that have come out in the past year or two, so there might be better values out there.