I spent the morning (July 20), using my new headphone/amp switcher, conducting extensive a/b comparisons of the ASG-2 and TG334. My findings were considerably different from Eke's.
Firstly I can agree that the G2 and TG334 share a similar frequency response in general. They both have strong bass presence with a forward midrange and gently downward sloping trouble; and they both present this sonic signature very well- both are engaging and a joy to listen to but I definitely hear significant differences, which affect the overall all feeling, emotion and tonality of presentation.
Both have very nice midranges but this is where I also find the most significant difference. The TG334 has noticeable more forward upper mids, which lend to a brighter overall signature with better transparency, smoother transients and wonderful delicacy in vocals. As a consequence the G2's mids sound not only much warmer but also have a rawness about them. I don't hear the delicacy in the G2 but rather a bluntness (in comparison). This may come across as less emotional or intimate in vocal performances but then lends to an aggressive rawness for rock, which I very much enjoy.
Paradoxically, even though the TG334 sounds brighter to me, the G2 has bit more treble presence. I really like the blend of the full range dynamic driver here, overlapped with the dual BA. Treble on the G2 has more weight and thus better timbral realism. The TG334 treble sounds slightly lighter (in comparison) and crisper. I really like the better articulation of the TG334 treble but would happily trade it for the tonality of the G2 treble.
The differences I hear in in the midrange and treble are born out in the various test tones I compared in my FreqGen app for the iPhone. The tones also showed very similar bass extension. I find the G2's bass notes harder edged but both seem to have very similar decay. Surprisingly the treble extension was basically equal as well using this app, although they have different elevations: between 7.5 and 8k for the G2 and the TG334 has less variance on either side of that range, with maybe a small peak at 10k.
I look forward to doing this same comparison again, once my custom AS-2 returns, as I remember it having a few differences in presentation and technicalities from the generic version. To tie back around to Eke's assessment, even though I hear them pretty different in mids and treble, I can consider them brothers from another mother- the G2 being the little brother of the TG334.
The ASG-2 is awesome fun, I whole heartedly recommend it!