Stephen Guo of Custom-iem.com is probably best known as being the North American rep for Unique Melody. Looking closely, you'll notice that he also sells cables and custom IEMs from Beat Audio, another company based in China. Stephen speaking both languages means he can bridge the gap between Chinese companies and buyers who wouldn't otherwise have access to them. He's mentioned to me in the past that he wouldn't mind offering more products if the right stuff came along.
It appears that time has come: xDuoo is a new company offering some interesting portable amps, some with built in DAC functionality, as well as a line of portable players and small desktop amps. Stephen will will be offering 3 models initially: the XP-1, the XD-01, and the UA-05. Let's take a look at them now.
This unit will sell for roughly $300 shipped. It's a slim portable amp/DAC based around a pair of Wolfson WM8740 DAC chips in dual differential mode. Amp section uses two OPA627 opamps and offers adjustable gain (+3dB or +7dB) as well as a selectable bass boost. It has the typical aux input via 3.5mm jack as well as a USB input for DAC duty. The USB input uses a TI PCM2706 which is limited to 16-bit/48kHz, which is done for a reason: the XP-1 is meant to be paired with Android phones. So far it's been confirmed to work with the popular Samsung Galaxy S3 as well as the larger Galaxy Note II and also the HTC One X. xDuoo claims Android 4.0 or newer should work but there's no guarantee - I found out the hard way that my Meizu MX 4-core does not work.
Not only does the XP-1 connect with phones as a DAC, but it can also charge the phone thanks to its large capacity battery. This function is activated with a switch so it is only used when needed. Nice.
This is another portable DAC/amp unit with a different focus. It uses a single Wolfson WM8740 paired with a Cirrus Logic CS8422 asynchronous sample rate converter for 24-bit/192kHz upsampling, which can be turned off or on by a rear panel switch. It has coaxial and optical digital inputs that accept 24/192 signals, and a USB input that goes as high as 24/96 thanks for the TAS1020B receiver. Gain is still adjustable from +3 dB to +9 dB. Not much is said about the amp section on this unit. This looks slightly thicker than the XP-1 but still on the compact side overall. Price should be around $300 shipped.
The UA-05 is the largest of the three models. It uses the same WM8740 DAC and TAS1020B for USB, but doesn't have any other digital inputs. The extra size is due to the unit having a far more powerful amp section than the others. It uses an unspecified dual opamp plus buffer stage with a max output of 800mW into a 32 ohm load. That's potent for a compact unit like this. Gain starts at +3dB but this time goes up to +17dB indicating this unit is ready to push some difficult headphones. The 1/4" headphone jack should make its intentions clear. Bass boost is also available. Price is not yet known.
I had a chance to demo a pre-production XP-1 and came away impressed. The size is perfect for carrying around along with a mid-sized phone, and it fit perfectly stacked on the Meizu MX 4-core. Unfortunately the Meizu doesn't seem to work in USB output mode, despite running Android 4.0, and I wasn't willing to flash a custom ROM to see if that worked. The XP-1 did work with my iPad via CCK.
The sound was very promising. The early unit I tried had a small problem with hiss which is supposedly fixed on the production model. But aside from that I heard excellent detail retrieval and very good dynamics. I ended up using it a lot with the V-MODA M80, and it did a wonderful job - hard hitting bass, smooth top end with good extension (limited only by the M80s slightly dark character). I later tried it with the Audio Technica AD2000 - not a headphone you would take with you on the go, but it sounded very controlled and fun. Some of my other portables didn't match well with the AD2K due to brightness and grain, but the XP-1 did a fine job.
I was limited in the amount of time I could spend with the unit so I don't have a definitive opinion at this point. But again - it sounded very promising. With the hiss eliminated and a compatible Android phone this thing would be a very competitive in the $300 bracket. I'm hoping to later demo one of the other models or possibly the finalized XP-1 so I'll update when I can.