I've been working on a review of the Audioengine D1 that I picked up at RMAF, for which I'll post most of it now. I'll add to this later when I am completely done, and also post it in the review section at that time. I felt bad for taking this long to get any impressions posted, so I wanted to make this post while I'm still 80-90% done. I put some of my key points in bold, in case you have to skim through quickly.
I didn't get to unbox it until a few weeks after I got it at RMAF so I'm still burning it in to my 300 hours standard, although they only recommend 50-100. The amp sounded good out of the box, but seems to become more transparent with burn-in, without other major changes in sonic character. So far I have used it as a USB DAC through Macbook Pro and Amarra Mini 2.2 audio player, with 24/96 and 16/44.1 lossless music. It has both a USB and optical input, but needs power via USB to run the optical DAC. I will report more on optical later, in my update.
For those that can't read the whole review, I find the D1 to have a nice headphone amp and great sounding RCA line-out. I think this DAC/amp should be a hit for the $169 price, if you don't need analog input with battery power for MP3 players. I'd venture to say it could have been sold for closer to $250-300, or more, without too many complaints about it not being worth the expense. I find the DAC and amp to be fairly uncolored, with good extension on the bass and treble, and no big dips or valleys in the sonic signature. And power is not lacking for a USB-only powered device.
Some specs I have are:
- 24/96 operation in both optical and USB
- Headphone output is 2V rms max, output impedance is 10 ohms, so 32 ohm HP would run about 100mw, and 300 ohm would run about 12mw
- RCA is 2V max as well, variable
- The audio signal is dual word clocked, and all internal bus is I2S
- USB receiver is TI 1020B
- Standard warranty for all Audioengine products is 3 years.
- I'm fairly sure I read somewhere that the DAC is the AKM4396 (like Slim Devices Transporter)
I've mostly been listening with some Jenna Labs re-cabled Denon D7000 (aka LA7000) and HiFiMan HE-300 from the second batch. I've also tried the Westone 4 and ES5 IEM, LCD-2 with Silver Dragon cable, HD600 with APS V3 cable, and HD800 with Locus-Design Hyperion cable. I still plan to try the D1 with my ESW-10JPN, HF-2, HE-500, and other more sensitive IEM. Of the full-size phones I've tried, I preferred the D1 most with the LCD-2 and LA7000, then HE-300 and HD-600 similarly. I really don't like the HD-800 with many of my other amps, except Eddie Current ZDT which drives the HD800 with absolute authority.
Note - I'm a strong advocate of system synergy. I don't even really enjoy the HD800 out of my beloved DACmini, and don't use them in my bedroom or laptop rig at all anymore. So, it's no surprise that while the D1 can drive the HD800 fairly loudly that I don't think the HD800 have the best synergy with it. I prefer the HD800 with a warmer sounding amp like the DACport or ALO Amphora, but even those still can't compare to the ZDT amp with HD800. I found with the LCD-2 and LA7000 that the D1 almost has better synergy than my DACport, because the D1 acts like it has more current reserves for loud listening even though the voltage swing is less. The DACport seems to peter out and run out of juice sooner than the D1 when pushing these low impedance phones to the limit. At more normal volumes the DACport edges ahead, but I slightly prefer having the extra power and more filled in mids of the D1 with the LCD-2.
With my IEM - the Westone 4 were good with the D1 and not too sensitive, but they still have that laid-back treble with the D1, and work better with my iBasso D4 which along with the needed treble also adds some space to the soundstage. The sonic synergy with my ES5 was excellent. However, the ES5 were a little too sensitive to use with the D1 if I wanted to sleep listening to music. At the lowest volumes that I could achieve before the sound would cut out suddenly, I found that the ES5 listening level was only about 2-3 dB below the levels that I would normally listen, so there was room to turn it up more, but not less. There is no dot or mark on the volume knob to aid in knowing where on the "clock" the volume is set.
I had to use a Westone volume attenuator with the ES5 to go quiet enough to listen while going to sleep. The system volume control does not affect the output volume for listening at extremely low volumes, so in that arena something like the uDAC-2 would come more in handy (at such low volumes lowering the system volume wont audibly hurt the sound). The D1 volume knob doesn't have a low volume channel imbalance, but it would go from no volume and then jump to a low volume in a very short range of turning the knob. In comparison, my original uDAC-2 had an imbalance at low volumes that necessitated using the system volume to go low enough to sleep with music, while the newer uDAC-2 SE has much better low volume control and doesn't need system volume attenuation to sleep with very sensitive IEM.
I also found that with the volume all the way down, with the ES5 I could hear a quiet high pitched whine if I plugged the D1 into my 8-port hub along with 5 others DACs, my EyeTV and external hard drive. When plugged directly into the USB port on my Macbook Pro the D1 was silent. With any of my full size phones the whine was inaudible, and pretty much gone with the less sensitive W4 as well. Again, solved by not plugging it into my full 8-port hub.
In comparison to the DACport, the Audioengine D1 is more forward sounding and slightly less spacious, but still possessing good timbre, tone and great micro-detail. The D1 might even offer slightly better extension in the treble for me. The DACport still seems to open up the performance a bit more over the D1, but mostly via the soundstage enhancements. It's this presentation where they differ most, so someone's tastes might even put the D1 ahead.
The D1 Image placement is fairly precise, and layering of instruments was pretty good. But the performance was more intimately placed and in a smaller venue than when listening with the DACport. However, the D1's DAC RCA line-out did seem to open things up more than the headphone amp, and with the D1 driving something like my SR-71b amp with balanced headphones I didn't notice much of a difference vs my $350 Pico DAC-only or $399 DACport as a pre-amp feeding the SR-71b.
In other comparisons I found that the D1's DAC is a bit better than the PCM2702E Japan DAC chip in my $250 Meier 3MOVE DAC/amp or Practical Devices XM5 (which is closer to $350 with optional BUF634 buffers and AD8065 opamps). Both of those amps have a somewhat forward presentation like the D1, but when using their built-in DAC's the they offer a slightly grainy texture to the sound that the D1 doesn't have. I've found in the past that these two amps are great but usually perform a bit better when using a better DAC via analog input, and with the D1 DAC it's no exception. The D1 feeding these amps sounds smoother and offers a better sense of space, micro-detail and transparency, allowing these amps to shine vs with their own DAC.
Those amps run on more powerful 9v power supplies with similar sound characteristics, but their DAC's are simply not as resolving. I also find that the D1 headphone output is good enough that the improvement in feeding the D1 into these portable amps is not huge, and may not be all that cost effective unless you really need their extra voltage swing or synergy for something like HD600/800. The 3MOVE was one of my favorite single ended portable amps for HD600/800, and the XM5 bested the 3MOVE with the LCD-2 and LA7000. However, the D1 seems to do just as well with the LA7000 and LCD-2 (and HE-300). As for features, neither of those amps offer 24/96 USB/optical input or line-out, but they do offer analog input and battery operation for digital music players and such.
My iBasso D4 uses dual Wolfson WM8740 DACs, and is upgraded with the HiFlight opamp kit. The D4 has a better DAC than the 3MOVE and XM5, and as a whole it seems to fall between the DACport and D1 when driving headphones (in 9v mode). The D4 has a similar soundstage to the DACport but slightly less warmth than D1 or DACport. Although it's limited to 16/48, that's perfectly fine with redbook CD rips. The opamp upgrade makes my iBasso D4 sound identical to a $350 Ray Samuels Audio Mustang amp (which is not very different from the DACport). The D4 also runs on 9v battery, with a little more power than the D1, but I still didn't think it performed as well with the low impedance LA7000 and LCD-2 when pushing them to high volumes. The 3MOVE and D4 both have a 5v mode in case your 9v battery is dead, but they really needed the 9v battery mode to perform their best.
The DACport obviously only runs on 5v USB power, but usually has a little more power output than the other 5v amps, although not as much as the amps in 9v mode. However, with the Denon D7000 and LCD-2 the Audioengine D1 sounds noticeably less strained at high volumes than the DACport, D4, or 3MOVE. It was closest to the XM5 in that regard. The Sennheiser HD600 and HD800 are 300 ohm and present a bigger challenge than low impedance phones, due to their need for a higher voltage swing. Not surprisingly the 9v amps offer more power to the 300 ohm phones, but those phones have an efficiency of over 100dB/mw and the D1's 12mw at 300 ohm provides very adequate volume levels. If I only owned the HD600/800 I'd still pick the 3MOVE, but using an upgraded source like the D1.
As for upcoming comparisons, I'll still try the D1 optical DAC via my Macbook Pro, but so far with Macbook Pro and OSX 10.6.8 the USB mode is quite good for the price. I also have a new Nuforce uDAC-2 SE with assynchronous USB mode, which I think sounds a bit more transparent and realistic/natural than the original uDAC-2. I'll be posting my impressions of the new uDAC-2 in it's own thread when I have time. But for now I'd say the D1 sounds at least as good as the more expensive assynch Nuforce DAC ($249), and both are a little better than my original uDAC-2. With more time I can decide whether either one is better than the other, or basically a draw.
In my opinion the Audioengine D1 is strong competition to the best of the portable DAC/amps I've previously reviewed in my big USB DAC/amp thread http://www.head-fi.org/t/306883/updated-2-22-review-13-usb-dac-amp-predator-pico-2-3move-d10-d3-d2-viper-boa-d1-lyrix-microamp-vivid-v1-nuforce-xm5/1080#post_7905352. And the RCA line-out DAC-only audio quality seems to be on par with more costly DAC's like my uDAC-2 and uDAC-2 SE, Pico Slim DAC-only or DACport (when used as a pre-amp).
In fact, while my more expensive opamp rolled iBasso D4 is technically slightly better and leads the top of my old portable USB DAC/amp review, I find myself using the Audioengine D1 (and uDAC-2 SE) more, while the D4 and others remain stowed away. This is partly because the D4 is mostly better in 9v mode, and at only 8-10 hours on a 9v battery (without internal charger) the D4 is not very convenient to use. With full size headphones the D4 in 5v mode is not nearly as inspiring. I also find the D1 is more versatile than my iBasso D4 because I can feed it's rear panel RCA line-out into my Audioengine A2 speakers, and then have the speakers shut off when I plug in a headphone. And, I can control the A2 speaker volume with the D1 volume knob (same with uDAC-2 SE), while the iBasso D4 has a fixed 1/8" line-out in the front. Plus the D1 still has better synergy with my LCD-2 if I want to listen at fairly stout volume levels (even if D4 is in 9v mode which benefits high impedance phones the most).
The DACport was reviewed by me previously, and I found I preferred it slightly over the iBasso D4. But it's even less convenient because I have to unplug the A2 speakers every time I plug in a headphone, and when I forget to turn down the speaker volume I hear a loud buzz as I unplug or plug-in the A2 speakers into the DACport. For IEM and very quiet listening the DACport is still my first choice, as it has excellent low volume channel balance and is very quiet. It's also still better with the majority of my full size phones, but not all of them (e.g. LCD-2 and LA7000).
So after this experience with trying different DACs in my Macbook Pro rig, I think for some people the choice may be made based more on features than sound, or based on synergy. If you want a nice DAC/amp with excellent RCA line-out, and don't need 9v battery power and analog input for an MP3 player, the D1 will fit the bill for a small portable laptop rig. It does have similar features to the new assynch uDAC-2. They're both small and portable and don't need wall power, have 24/96 USB input and a slightly forward or intimate soundstage with imaging like the 3MOVE, with good sounding headphone amps and excellent RCA line-out quality. And they can both handle low impedance and high impedance phones, although some better than others.
But they do have some different feature sets. Where the D1 has a 24/96 optical input, the uDAC-2 SE offers a 24/96 coax S/PDIF output instead. The uDAC-2 SE is smaller, but the D1 has a little more juice for the low-impedance LCD-2 and LA7000. And the uDAC-2 SE will allow listening to very sensitive IEM at lower volumes before needing to resort to a volume attenuator, but only the most sensitive IEM will need the attenuator with the D1, and that's mainly if you go to sleep listening to music with them.
In my case, at this price point and level of performance, I think the D1 is a no-brainer. I've sold half of the USB DAC/amps in my big review over the years, but the D1 isn't going anywhere. While you can't feed it into a nicer DAC like with the uDAC-2's coax output, fewer high end DACs come without USB input. And the optical input of the D1 could be more handy if you want to add a CD/DVD player to your rig to use when your laptop is asleep.