JDS Labs Assembled Objective2 Headphone Amplifier

I came upon the article by the navguy and almost instantly ordered a kit. I was amazed at the sound of the kit, so later I ordered one O2+dac. I am an electronic technician, so I have assembled and purchased many headphone amplifiers and after testing many I am convinced that this O2, the concept of Navguy, is one of the best amplifiers in the market. You can also try the Cmoybb to hear a good bass and the clear sound will amaze you. I recommend these products to everyone. Period.

 
Meant to be married to the OL DAC, the O2 headphone amp matches it in shape, size and simplicity. What’s neat about the O2 is that JDS Labs allows for some simple customizations—you can choose the headphone jack size (3.5mm or ¼”), input type (RCA or 3.5mm), gain levels, and power jack location (front or rear panel), and whether to have it with or without a built-in DAC and lithium batteries for portable use. I went with a rear-mounted power jack and RCA input, so my front panel is nice and simple with just the power button, headphone jack, volume knob, gain button and a red LED power indicator (why red instead of green to match the OL DAC? I don’t know, but it kind of bothers my OCD).

So how’s the little black box sound? Well, it follows the open source amplifier design from the aforementioned NwAvGuy. In other words, it targets benchmark performance at a budget cost ($129). So, much like the OL DAC, the O2 amp aims for transparency. Or maybe a better way to put it is simplicity. 

For those of you that are used to colored amps, there’s nothing romantic about the O2. In fact, it’s likely to come off as a bit dry, a bit sterile, a bit, well, boring, just like the OL DAC. That is, unless your DAC is colored in another way. After all, all the O2 really does is amplify the signal in front of it, which means a great recording, a nice DAC and a stellar sounding headphone or IEM is what’s needed to put you on the path to #AudioNirvana.

The best thing about the O2, sonically speaking, is its versatility. It has the power and dynamic range to drive anything from a sensitive IEM to a power hungry dynamic headphone with authority. The semi-picky Sennheiser HD650, for example, gets plenty loud and hits with modest authority in high-gain mode. The O2 can also play any genre of music well, because, well, you’re hearing the music and the rest of your equipment for what it is. The caveat here is that you need to plan for this. Meaning, the O2 is going to do absolutely nothing to hide poor recordings, and if you favor a darker, warmer sound signature, you’ll want to choose a headphone with those characteristics rather than something analytical like the reference level AKG K701. Or, you could always dabble with some EQ software to fine tune your setup. 

With the OL/O2 combo, which is what I assume a lot of you reading this review are considering purchasing, you’re getting a pair of neutral performers, nothing more, nothing less. This stack isn’t going to romanticize your music collection. Rather, it’s going to allow you to focus on the music and hone your efforts on choosing the IEM or headphone that best suits your musical taste. 

I’ve mainly been running the rounds with the Audioquest Nighthawk, Beyerdynamic Amiron Home, Meze Audio 99 Classics and Sennheiser HD650. The OL/O2 drives each of these headphones with ease and enjoyment, although none come off as being quite as airy, lush or three-dimensional as when pushed with a powerful tube amp (just my personal preference), the warm characteristics of each is conveyed cleanly and with good. Although these are all darker sounding headphone, I liked the pairings because it brought some balance to the neutrality of the OL/O2 stack. The consistent instrument separation and detail retrieval of the OL/O2 pairing is solid. The sound stage is modest, extending maybe three to four inches out around the head. Stereo imaging is dead center, although I do selfishly lust for a more holographic presentation. As someone who favors really lush sounding gear, this little stack can sound a bit flat to my ears—bass notes hit with impact, but often lack resonance; mids are clear, but are light on warmth; treble is crisp and detailed, and never too brittle, but airiness and texture seem overly controlled. But all of this is inherent in neutral, transparent solid state amps and DACs. Boring can also be better; the neutrality of this combo makes it an excellent setup for audio purists and gear reviewers because it reveals more accurately what a particular recording, headphone or IEM can and cannot do. 

Overall, I generalize the OL/O2 stack as being crisp, clear, controlled and consistent. Sure, it can be boring for those that favor the ooey gooey goodness of lush and distorted tube gear, but boring isn’t always bad. In fact, these little black boxes are probably one of the best places to start for new budget-minded audiophiles looking to learn just what it is they like and lust for. 

I read about this device online and the reviews were very positive - so positive that I jumped in.  It was my first headphone amp — I purchased my second, the fiio a5, shortly afterwards.
 
Take into consideration I am an amateur audio geek...
 
It is just what everyone says about it; zero background noise; clean sound; no extra color.  I did also read that it was a little on the large size to be considered portable, and I agree that it is.  However it will fit in the back pocket of my Levi's so I'm still considering it portable.
 
After comparing it to the fiio a5 for a week I must say I prefer the Objective2.  The "uncolored" sound is really more my style.  I wasn't sure where I fell on that spectrum...  But after comparing, I get it.  The objective2 is cleaner, more open.  You are not going to find something like a tube amp warmth.  But what you will find is your really great recordings in crystal clarity.
 
Physically it's a nice solid piece of equipment.  It has a single red light when it's on.  The battery power so far seems to be in line with how it's advertised.  I do like that I can replace the batteries easily if I needed to.  Little things like that make this a special piece of equipment.  The volume control has a wide range so you can adjust it to very specific levels.  JDS labs has responded to my queries in almost real time.  They are very friendly and accessible.