Disclaimer: This is going to be a long post, that I'll divide into a few sections. First up will be my story, with all the details you could want. Second will be my review of the products, and last will be my opinions of Mayflower. Feel free to skip as much as you want or read the whole thing.
My Story
About a month or so before the Audiophile Myths videos started being posted, I started seriously considering upgrading my audio chain from onboard PC audio to an external DAC and headphone amplifier. Being a Head-Fi member (with a permanent skeptics hat on), I began to do some research. The two setups that really caught my eye, though, were the Schiit Audio Modi + Magni (which I'll refer to as either the Schiit Stack or the M&M stack) and the O2/ODAC.
While a lot of posts on head-fi are heavily biased and don't necessarily portray reality, most of the skeptical community seemed to appreciate the O2/ODAC combo. This lead me to the nwavguy blogspot page, and a lot of reading.
I learned a lot from nwavguy's scientific explanations of everything, but what really sold me was his absolute confidence. On his website, nwavguy set up a very simple challenge: anyone who thought they could tell the difference in a blind listening test between an O2/ODAC combo and his $1k Benchmark Dac-1 (widely regarded as one of the most accurate DACs money can buy) would receive a $500 donation to the charity of their choice. If the challenger lost, they would have to make a donation to the charity of nwavguy's choice. In all of the time before nwavguy dropped off the face of the planet, not one challenger arose.
This had me sold. So, off I went to find my Objective stack, and this presented me with options. Since the O2 and ODAC were open source, the schematics were readily available online and anyone could build one for themselves or sell them to others. Since I don't have any experience soldering, I set out to find a manufacturer I could trust at a decent price point. The two primary builders of the O2 in the US are JDS Labs and Mayflower. Since I'd been hearing great things from people I respect (such as barnacules, Linus, and Logan) and Mayflower's prices are lower, I was sold. I ordered an O2 with an integrated ODAC, and anxiously awaited it's arrival.
Unfortunately, I made the mistake of ordering during the Christmas / holiday rush, and didn't see my new toy for nearly a month after I placed my order, but I couldn't complain too much. Back orders are back orders. However, I noticed something strange about my unit. I returned from work one night and fired it up. I turned on some music, and was horrified by the amount of static I was receiving. I contacted Tyler from Mayflower about this issue, and in the meantime set out to try troubleshooting it myself. Long story short, I found out that after about 10 minutes of non-use, the static would return. However, if I re-seated the USB cable before use, I wouldn't have any issues. I decided that I could live with this small foible, and decided to just drop the issue. I didn't want to wait a couple of weeks for an RMA, and other than a small inconvenience, it worked admirably. So, for the last few months, I just put up with it, and everything was pretty much fine.
Then, within the last month, things took a turn for the worse. I started getting random hangs in foobar that could only be solved by (once again) re-seating the USB cable. It was added frustration, but I was in denial about the inevitability of an RMA. Then things got ugly: it just quit. For about half an hour, I couldn't get the thing to work at all. I tried different usb cables and a couple different computers. It refused to even be recognized by Windows. Then, as if it had a will of it's own, it came back to life. This was not an acceptable flaw, so I once again emailed Tyler. He agreed that it wasn't acceptable and immediately agreed to replace my unit. I asked whether or not I could get a standalone O2 with rear power and a standalone ODAC if I paid the difference in cost, and he happily agreed. So, after a couple of really crazy weeks, life gave me a chance to relax a bit, and I sent off my unit.
Now I'm sure the majority of you have probably heard the phrase, "You don't know what you have until it's gone." Most of the time it's in reference to loved ones, but I think I finally figured out what it's really about: a good audio chain. I waited a few insufferable weeks for packages to be shipped both ways, and finally got my new O2 and ODAC.
Aside: One thing worth noting is that Tyler was apparently unable to reproduce the problems I was having. It was a weird situation, and one of those questions in life that I probably won't receive the answer to, but at this point it doesn't matter.
I quickly plugged everything in, queued up my favorite album, and hit play! I waited a few seconds in stunned silence, and my heart sank into my stomach. Absolutely no signal. Again, I went through all the troubleshooting I could possibly think of, and did some research on the internet. I stumbled across a post in some forum or another about a guy who had assembled his own ODAC and wasn't receiving any audio output either. The suggestion that was given as to the source of his problem was that two jumpers on the bottom of the board (J1 and J2) were not soldered together. Having these jumpers connected was vital for connecting the DAC's output with the 3.5mm jack, so I opened up my ODAC, and lo! and behold! the jumpers were not soldered. As a quick test to see if it was indeed the problem, I made a few quick "bridges" out of bits of old wire, held them down to the contacts, and played some music. Worked like a charm. So, I sent Tyler one last batch of emails telling him about the QC issue, and had my friend solder the contacts for me a few hours ago. So far I haven't had any issues.
ODAC Review
I'm perfectly confident that the ODAC is about as transparent as they come.
Works on all versions of Windows from XP onward, OSX, and Linux.
USB input only.
Standard version comes with a 3.5mm (1/8" mini-stereo) output, but shouldn't be too hard to modify to 1/4" or RCA outputs.
Can also be inserted into the O2's enclosure and hardwired to the amp (although in the standard enclosure this means you lose the option to run on battery power as the ODAC sits in the spot the batteries normally occupy. Similar enclosures exist that would allow the ODAC to live above the batteries, but additional supports would be needed).
And that's all I have to say about that.
O2 Review
This thing has enough power to turn my HiFiMan HE-400's into a small pair of speakers. Not only that but it's a very clean amp that doesn't seem to flavor the sound. However, (and this could all be psychological) it seems to handle the lower frequencies much better than my onboard sound or the absolutely awful headphone amplifier that's built into my AVR. It does what any good amplifier should (make things louder) and little else (it also helps with damping if you have very low impedance headphones). If you're looking for something to color your sound, look elsewhere.
My Thoughts on Mayflower
Overall, I have to say that Mayflower is doing a good job. They're a small company that seems like it's dealing with a few growing pains, but they handled the issues that I've had quite well. My only advice would be to pay closer attention in QC (for my latter ODAC. I'm pretty sure that first one was a fluke that no reasonable QC would have caught). I'm not quite sure how my second ODAC made it out of the door with no solder on those jumpers, and with a QA stamp, no less. Other than that, they've done a stellar job, and they've created a happy customer. I'm interested to see what other amps Tyler may come up with, and may end up purchasing one for myself when they arrive. Keep up the good work.