MR Mateo Head Bought his first Headphone Amp! PART 1
If you hate reading, I'll cut to the chase: It was the best amp I could find, and I really, really like it. It seems to be a good deal @160 all in, but I still think $100 would make it a market crushing steal.
Today I received my O2 Amp from JDS Labs - a second guilty purchase following the HE-400s. I ordered it with the Triad 12 VAC 200a adapter. I also opted for "stock" gain set at 2.5x and 6.5x and a black faceplate, which I thought was classier looking than the silver one. That said, I despise our world for seeming to always paint everything black or gray. This is why I like my headphones BLUE! Even if its plastic . . .
Why did I want an Amp???
I bought the amp because I found my computer had inadequete power for High Dynamic Range Recordings (HDR). HDR recordings are those where the difference between the loudest sound, and softest sound, can have a very large spread. In my case, this occurs with some classical music, DVDs, and even Mp3s I own. In effect I cannot reach loud sound levels with these recordings, sort of like being stuck in a car that needs to hit the highway but is stuck in 1st gear.
Why did I choose the O2?
First I determined that the HE-400s might require as much as 0.5-1 watt in order to achieve 100-120 dB. This is far louder than I would ever actually listen (and maybe louder than they can actually play), but I figured this would give me "headroom" and help me achieve good volume with the cans no matter what I was doing. I looked all over the place for a reasonably priced amps of all kinds, including USB/DAC combo drives, high-end amps, even external sound cards with jacked up headphone ports. My experience with audio has taught me that it is generally stupid to buy anything which might NEED x watts rms to run to its potential, and then give it half that power. I consider headphones generally no different, though I am a firm believer that for 90% of headphones out there, buying amps and DACs is a total waste of money. If you really crave a better sound, put the bucks into the headphones (speakers).
Amp Shopping Sucks:
About 90% of the amps were eliminated based on the following criteria:
a) Unpublished specs: If you won't report your power at multiple impedances, I won't buy your amp. If I can't derive values from copious calculations generated with the help of the geniuses here at head-fi and your limited specs, you are really, really out of the running. That was easy.
b) Price: As in, holy s*** you charge that much for 1 freaking watt? I once owned 738 watts of class a/b goodness from TWO amps in a car for less than that. $200 bucks is a damn generous budget, IMHO, considering its far more than most good soundcards, most all good USB/DAC combos, and could even buy a decent receiver which probably has a decent headphone jack onboard (and a sh**load of inputs and outputs as well as power for big awesome speakers). Actually $200 can buy some damn nice headphones too.
c) Assumed performance: If you want 0.5-1 watt, you are not going to get it from a USB-powered source. You just aren't. It took a lot of math to prove this to myself. Thanks, Fiio.
d) Output Impedance: Surprisingly, this eliminated most decent inexpensive amps, and even expensive soundcards. They damn near all had 10 Ohm output impedance, which kills power at higher impedances. Following the 1/8 rule, it also optimizes these amps for headphones of 80 ohms or more. Being that the HE-400s are about 35-50 Ohms, I looked for 4-6 Ohms MAX at the output stage. Actually, I am quite surprised that this is so common. Most of my cheapy headphones are 16-32 ohms, and as a general rule amplifiers won't deliver much power into 300 - 600 ohm loads common at the high-end of cans. Even 100 ohms is high enough to crush a lot of consumer amps I looked at.
e) Tube Amps: I don't want to buy tubes. I don't. I don't care how awesome tube amps are. I don't want to know about it. They cost more money, and sooner or later they burn out. My parents have a Sony DLP TV which goes through 1-2 bulbs a year @$300 bucks. The TV is sick, but jeez. Were it not for warranty games, they could've bought me a 60" by now with a Playstation. Why are their so many tube amps?
Choose Something, Stupid:
After much pain, then, it came down to the HRT Headtstreamer, Schiit Asgard, and Objective O2. The headstreamer doesn't have nearly the power I was looking for, despite meeting other criteria. The Asgard was over budget, and reviewers claim it emitted a steady electric hum. That said, it can do about 1 W @ 50 Ohms and likely is a good amp with plenty of power. For the price, I don't like the metal power switch in the rear, and I think it should offer a 3.5 mm in, RCA in, and what the hell, an optical or coaxial digital jack and not just a set of RCAs. I am ruthless and greedy, I know.
So, there wasn't much choice. But I believed in the O2's "open source design", and trusted the specs. From those specs, I derived a power curve which suggested 440 mWs on batteries, and 706 mWs on AC @ 50 ohms. In theory, then, very close to meeting (or actually meeting) my 120 dB performance challenge. Because the O2 has built-in current limiting however, those are peak values and represent max power before audible distortion. Now throw in 2.5x and 6.5x gain switches, and unknown source current (I think 1 Vrms, I don't know), and we have what I call an educated guess that happiness is assured. $160 bucks was pushing it, but I couldn't find anything better. Does anyone else think JDS labs KNOWs that??? the $30-$50 dollar DIY wonder amp selling for three times the price? That's what I get for being a non-engineer I guess.
Description of the O2:
Mine shipped quickly and arrived in about 3 business days - but I had to sit out the weekend. I have to say, it looks great in black, and it quite adorable. It is like the baby of my car amp. Seriously, its like 2 packs of bicycle cars side by side (or butts, if you smoke). The batteries inside give it a "substantial" weight, and it all around seems very well put together. The volume knob has a good feel, and the fit and finish are a 4/5. Their was some slight mis-alignment percieved between I/O jacks and the power cord didn't just "slide" or click in at first. The gain and power switch feel a little low rent, but otherwise, its nice.
Mine also came with small 3M rubber feet stick-ons, a nice touch (which will probably fall off 1 at a time). It came out of the box ready to go, hooked up quickly, and having all the jacks in the front wasn't as bad as I thought. It even makes sense when you think about it (the thing won't "suspend" between my headphones and its input jacks). Also, I can stand it on its ass or 2 sides. Its an accesible design choice, and it would be fun to velcro the thing under my desk or somewhere handy. I could also leave it in a bag, and use it to "stealthily" power my phones when at a library or some other place.
I disagree with others that do not consider this thing portable. It wouldn't go in my pocket or jogging, sure, but I can imgaine carrying it in a computer bag or something, to provide better fidelity wherever I ended up. I will concede however, that I might worry a little about the buttons and knob taking knocks, and maybe the batteries inside dislodging from a bad drop. It looks like a baby desktop amp, and that is perhaps its best use. I like the red LED power light, but otherwise am used to devices giving me something more specific, like, "4 hrs left", or, "92%". Then again, those things are hardly ever accurate, and simplicity is nice for a change.
Of course, none of this aggravating reading means s*** if it sounds like s***. Next up is part 2 - SOUND!