Oh boy where to start. (Don't take offence this is supposed to be a constructive debate - You would have seen one of my more offending posts by now - its blatant)
I get NuForce, iBasso, and Schiit.
I don't like nuforce because of the design by ear. And ****ttttttt measurements.
I don't like iBasso because of quoting component specs for final specs.
I don't like Schiit because of how they handled the Asgard fiasco, namely by flat out denying and avoiding it, then coming back later and saying whoops. Versus Hifiman with the glitch with the HE-400 where they looked into it first and then publicly announced the mistake.
But AudioGD... I can't group them in the same boat. I mean Kingwa did win the Texus Instuments competition for amp building, And there is no way in hell they award it to some guy who designs by ear when the entire company exists solely on measurements and implementation. And Yes I don't like how he throws around some bigger names Like how he somewhat copied Mark Levinson's current based volume control (which IMHO kicks the snot out of stupid pots.) But he also posts measurements, and he is of the uncoloured opinion, he designs his master series gear to be as transparent as possible.
I also won't knock the revisions, Amps get old, the new ones coming out today clobber the ones from 5 years ago at the same price. Technology improves, and so will implementation. GIve him credit for keeping them up to date.
And Yulong? Fek only knows why you don't like him, he also design for specs, BUT he designs for sound afterwords (his reference gear includes the notorious HD800) which probably explains why his D18 DAC can measure so well and still sound like vinyl, which is a mean challenge.
I won't lie hype exists, and its bad.
Silver cables are a joke, a good OFC copper that doesn't go prison style on you is all good.
Talking of mods, I just discovered that the previous owner of my D7000 placed some foam rings between the pads and the cups, which gave it more soundstage but made it u-shaped as hell and treble of death, and it annoyed the hell out of me, now i just removed it and it's a completely different headphone. RAWR, And I have moaned a few times about the treble on these puppies. Which is now not a problem..... kak.
And on a side note @Chris, audio IMO should be based on solid theory and measurements, but if you have ever opamp rolled (where theoretically they will have no difference in sound from one another) you will know there are factors that cannot be measured, And level of euphoria is one of them (and the reason I love my Denon D7000, the king of fun after all) So having measurements is all good, but it should still sound good. And thats often the criticism with the ODAC and the O2, but its not really a problem with a headphone like the D7000 which has a very strong character and dominates the components upstream. So they suit the Denons fine, but something a bit more influenced by the colour of the upstream components could very well sound bad, cold, lifeless.
No offense taken, you make great points! I'm mostly against audio gd because of my experience with their sparrow :/ I'm sure they put out some good products, I was just burnt by them. I don't even remember why I don't like Yulong anymore. I should stop commenting on them. I haven't heard any of their gear.
Hey, there is difference between opamps and it can be meausred! Sometimes you put in the wrong one and it goes all haywire and affects the sound. Not in a technically good way, but sometimes people think it sounds good. Basically, I feel most op amps used properly shouldn't be much different. But, when you are just swapping them out randomly, bad things can happen.
I like the sound of the odac/o2 even on very transparent headphones (paradox, for example). But, it might not be everyone's cup of tea. I dunno, if you like the sound of something, stick with it, that's all I can recommend anymore X.x That and just try to get your hands on as much gear as you can to figure out what you like, what you hate, and what you really like.