Disclaimer: the statements I'm about to make apply to any Jung multiloop amp. I'm here to talk about the circuit, not the boards specifically.
Quote:
| The META seems to be the newest and greatest DIY or order from JMT style amp. |
"The greatest", no.
Quote:
| is it's design a superority, where the difference in the internal componants is what determines how good it is? |
A bit of both.
A major part of the sonic quality of a DIY amp is in the components, since parts costs is always a small portion of the cost of any commercial amp. It's not that commercial vendors have horrendously unfair markups or anything like that, it's just a normal side-effect of the system. Therefore, it's typical to see $1 op-amps used in commercial amps, whereas almost all DIY amps that use op-amps use chips costing at least $4; it's not atypical to see DIY amps with $30 in op-amps inside.
As far as design superiority goes, I wouldn't classify the Jung multiloop variants as "superior designs" without qualification. All of the amps you mentioned have made good design choices, but they all have different design targets. So, which one is flatly "superior"? All of them, and none of them.
Instead, I offer some distinctions:
DIY amps based on the Jung multiloop topology typically use high-end op-amps and monolithic buffers. (They can also use op-amps all the way through -- that is, additional op-amps in place of the buffers.) The op-amp contributes the most to the "flavor" of the amplifier's sound; since Jung multiloop amps can use many different op-amps, you can get quite different sounds from different Jung multiloop amps. The next most important contributor to the sound of the amp is the buffering setup used, and this can also vary greatly between units. Finally, the purpose of the Jung multiloop topology is to reduce distortion to very low levels; this is successful to differing degrees in different amps. About the only thing you can say for certain is that a competently-built Jung multiloop amp is a good value for the money. That is, an amp costing $50 in parts will be good, as will a $200 amp; the $200 one will sound better, but not 4 times better.
The Creek OBH-11 is a hybrid op-amp and discrete transistor design. I'm not aware of all the details, but what I do know is that it uses an inexpensive op-amp chosen for its low distortion. This chip provides the voltage gain, and it's followed by a discrete transistor buffer for handling the difficult load of the headphones. The buffer is a simple design, so it shouldn't be compared to the complicated monolithic buffers used in Jung mulitloop amps. Also, it's not clear whether the Creek's buffer is inside the feedback loop of the op-amp, which would affect distortion. Inside the loop is better, in this regard. Because this amp has some of its power regulation inside the amp box, it isn't a great idea to try to rig a battery pack for this amp, as it would be an inefficient setup.
Aside: This is one big advantage to DIY: it's often simple to translate a design from portable use to wall-power and vice versa. With commercial amps, it's usually only possible to take a portable amp and power it from the wall; wall-powered commercial amps tend to be unsuitable for portable use.
Getting back on track....
The Grado RA-1 is a very simple design with a highly neutral and inexpensive op-amp. There is no buffering in this design. Most of the value of this amp is in its low-power features (i.e. it runs for a long time from batteries), the neat case, and the exceptional neutrality. You can get similar neutrality from a Jung multiloop amp by using the same op-amp, but most people want a bit more "flavor" in their amp.
The Gilmore is entirely discrete. This makes it a unique design, unlike anything else. It's difficult to compare it to an op-amp/buffer setup, but basically you could say that the Gimore has aspects of both: it has voltage gain and current gain. I'm not aware of anyone who hasn't placed the Gilmore above any META42, sonically. (This would also place it above the other current Jung multioop headphone amp designs, the MINT and the Xin Supermini.) It is, however, quite a bit more expensive than these designs, and it is not really sane to use it portably. Some have attempted portable Gilmores, but only as a lark.
The Melos is a tube design, and I'm not familiar with it at all, so it's really hard to compare it to all of these solid state designs. If you like tubes, go for it.
The HPA-1 I'm also unfamiliar with.
I must point out that this just skims the surface. My point here is not to give you an all-inclusive guide to all the amplifiers you've talked about. The point is that these are all different designs, with different strengths. You really should do a search for detailed reviews of each of these designs, especially comparative ones. It's kind of meaningless to talk about "the greatest headphone amplifier" without comparison.
