Quote:
Me x3: "The rule" makes sure you won't hear the effects of low damping factor, but these effects are not as bad in real life as some suggest. More so, there's plenty of cases were people prefer a relatively low damping factor because of the added warmth/punch. There's no such as thing as unpredictable frequency response once you know the shape of the impedance vs frequency plot of your headphones. For the Beyers DT, this is a slight bump in the mid-bass and a slight raise in the highest treble (well over 10kHz). So when you pair them with an amp with low damping factor what you get is a slight boost in the mid-bass and a slight boost (almost inaudible) in the highest treble.
I've tried my DT880 250 Ohm and DT990 250 Ohm plugged into the headphone jack of a Yamaha Integrated Amplifier with an output impedance of 470 Ohm.
They sounded just like that, warmer, more forgiving, not the last word in transparency in the bass region but still clear and very enjoyable.
If specs are true, the UAC-3 will drive DT770 32 Ohm version just fine (not much extra room, but fine)
The V-Moda M100 has a flat impedance and thus it's almost not affected at all by the low damping factor. You'll hear it as it is.
And it's very easy to drive, 20mW is tons of power for the M100.
Similarly the Yamaha Pro400 and Pro500 are well regarded bassy and very easy to drive headphones.
In the end, personal preferences play an important role, but this are all good alternatives.
you're equivocating two slightly dissimilar things: combined voltage drop and damping factor.
A headphone with a flat impedance curve won't "be almost unaffected by lack of damping factor." What impedance curves tell you is the power demands the headphone places on an amp, and how steady it needs its voltage supply to be over a range of impedances. The HD650, for example, needs an amp with very little voltage drop, so it needs an amp that has relatively similar amounts of voltage* available at its average impedance (300 ohms) and its peak impedance (500 ohms @ 100 Hz), otherwise it experiences clipped bass, which sounds wooly and lifeless. This is why Sennheiser engineers, despite the HD6XX series having relatively high impedance, say their headphones are designed for 0 ohm output impedance amps, because while damping factor isn't an issue, voltage drop is. A headphone with a flat impedance curve, on the other hand, doesn't have this worry, and you only need to concern yourself with the amp's power delivery at a single impedance and damping factor. The larger the amp's output impedance, the more important this becomes, as voltage drop becomes comparatively larger. With a 0 ohm output impedance amp (practically defined as anything with output impedance of 1 ohm or less), voltage drop is stable, and the headphone performs without any voltage drop across the frequency response, ie you get the frequency response you bargained for. Some people like the sound of some headphones with a large voltage drop because of this FR alteration, but in my experience, it almost always does more damage than good, as you're literally getting clipping in certain frequencies but not others.
Damping factor, on the other hand, has to do with a headphone's ability to "bounce back" against the impedance of the source, and thus deliver quick, dynamic performance. Under-damped headphones sound the opposite of punchy, instead sounding much more "slushy." Now, yes, some people prefer under-damped headphones, because it can cause the bass to be very boomy, with longer decay, while some headphones can sound overly dry and analytical if they're properly damped. On some headphones it's not particularly a big deal. My Shure SRH840, for example, can take output impedances a good bit above its recommended 6 ohms and sound fine. But my THX00 starts to sound wooly with any amp over 1 ohm, even though it should be okay with anything up to 4 ohms.
Also, for the OP, the Zoom is one of the worst headphone amps people pay money for. It's got the double downside of being high output impedance *and* underpowered. Honestly it will probably sound worse than simply playing out of your phone. That isn't to say it can't sound okay in certain scenarios, but to be blunt, it's a piece of junk. Literally the only things you really need a headphone amp to do is provide enough power with a low enough output impedance to allow your headphones to shine. The Zoom fails in both of those regards. Its high output impedance means that you get a large voltage drop and insufficient damping. This will render your headphones comparatively lifeless in comparison to an amp with more appropriate specifications. I hate to be blunt, but you really shouldn't worry about spending money on good headphones if you're using the Zoom.
That being said, the UAC-2 is a good DAC. I think of it as a DAC that has an emergency amp built in.
* [note, I originally said current here, meant to say voltage since I am talking about voltage drop here]