Just wanted to repaste some impressions I made in another thread:
Build: The JDS labs build is very nice. Solid aluminium casing, everything fits together nicely. Again I can say that the 3D renders don't really do it justice, so here's a picture for you to peek at.
My one complaint about the build is that the 3.5mm socket feels a little stiff when inserting a jack, and possibly contributing to this is that the socket move slightly when using them, as if the face plate has a little room for the sockets to wiggle. It's a relatively minor issue though, and honestly what I would expect out of a amp built on a DIY design. The 3.5mm headphone jack I'm very pleased with since I don't have to do any adapter swapping between my phone and this amp. The 3.5mm line in input is a little clunky - I'm using a 3.5mm to RCA adapter to go to my Music Streamer II+. This makes me ardently hope the ODA has a preamp out and RCA line ins.
The whole unit is about the length and width of my wallet and the thickness slightly thicker than a VHS tape. It makes me scared that some people here might not know how thick a video tape is. I can't imagine using this as a pocketable headphone amp, but it seems the right size to toke around with my 11" Macbook Air and rock it out in a library or a park with the battery.
Sound: This is the real treat. while I am not the biggest believer in amps making a huge difference in sound, I have to say I am pretty darn impressed by this amp. It is very noticeably cleaner then the Schiit Asgard it replaced, the sound being grain free, rich and full of authority. Everything sounds smooth, detailed and clean. What is most striking to me is the sense of authority it has lent to the bass of my lighter cans - the Z1000 sounds nice and liquid on it, with deep bass extension. It is something I suspect I missed since I originally bought them, when I had a Black Cube Linear to demo them on. The AD900 sounds clean and sweet on it as well. I have to say that the lack of grain has made both the Z1000 and the AD900 a lot easier to listen to, compared to when they would have drier, granier treble on the Asgard. Lastly and most happily, my old RE0 which was the start of my Head-fi hobby sounds, well, essentially as good once paired with the O2 as any other high end IEM I've bought since then.
I don't know enough or have heard enough amps to say whether or not this amp has a particular sound - I am going to take it at face value that the designer of the amp was going for a neutral amp with low distortion and harmonics, and that is what I seem to be hearing. If I had one word for it, it would be: clean.
Now here's the one troubling note. Yes, the JDS labs O2 has a 2.5x and 6x gain switch. I'm finding that on the high gain setting, there is noticeable distortion. This isn't the high volume kind of distortion, but fluttering noises I'm getting at normal volumes. I'm running off a 14vac adapter. Now, I don't have any high impedance cans to test the O2 with so I don't know if this is an issue that is happening because I'm trying to use high gain with low impedance headphones (I don't know enough about electronics) or because of some fault. Since the amp seems to have more than enough headroom at 2.5x with all my headphones (I'm not even going to 12 o clock on the volume knob on any of my gear) I won't really use the 6x gain mode, but I have sent off an enquiry to JDSLabs about it.
Edit: Reviewing the instructions that came with the amp (duh) it seems I may be causing distortion because at 6x gain and the 2v + output of the Music Streamer is overloading the gain stage. Oops!
I was twittering to Mike from Headfonia about the O2, and he pointed out that the JDSLabs O2 he had also had degraded performance on the high gain mode (which is what prompted me to try it), though I do not know if it is quite as bad as what I am hearing. He also pointed out that the Epiphany Acoustics model has a 1x / 2.5x gain switch, and that the 1x gain setting was even better. Again, I can't confirm this, and I don't even know enough about gain to really comment on it - just something to note if you are thinking between the JDS and the Epiphany model. I went with JDSLabs because they are supposedly the more reputable company, but the Epiphany does include a local power adapter for around the same price. All I can say is that on the default 2.5x gain mode I'm more than pleased with the performance. It's dead quiet, even on AC power, with no hum or hissing.
Overall for $150 I think anyone with some nice headphones owes it to themselves to give this a go and hear nwavguy's statement with their own ears so to speak. Again, I don't know enough about electronics or amplifiers to say one way or the other whether the technical aspects of his implementation are correct, but I do appreciate his transparency in designing and selling this amp. And I appreciate the amp's own transparency very much. :3
Edited by a_recording - 2/23/12 at 3:18am
