Review - Audioengine D2 Wireless Hi-Res USB/Optical SPDIF DAC & Transport
Aug 24, 2017 at 1:05 AM Thread Starter Post #1 of 7


Headphoneus Supremus
Aug 18, 2007
This isn't gonna be like one of my previous reviews. It's a belated re-review of the Audioengine D2 DAC, which I believe I posted to Computer Audio where it didn't belong last December 2016, and it may have been moved to this forum and subsequently lost somehow. It was pointed out as missing this January, after my MacBook had a serious crash that wiped out everything new from before Xmas break thru the 12th of January, so my 1st review is gone forever.

To complicate things, I developed a much more severe case of tinnitus in my right ear after an infection (MRI normal, but definite hearing loss above 10Khz with the ringing at about 10-12KHz). So I am having to do much of this review based on memory from when I had better hearing. But I felt that I should at least post the impressions that I had when comparing the Audioengine D2 to my Airport Express, CEntrance DACmini, and my PS Audio Perfectwave DAC Mk2 (PWD) before my condition worsened.

I didn't feel right about not re-doing my review, especially since I genuinely enjoy and highly recommend the product. They are currently available on Amazon for $399 which is a great price for the sound and features it offers.

Screenshot 2017-08-23 22.59.01.png

I have been very impressed with the D2 as the best wireless DAC that I have tried. My Perfectwave DAC Mk2 has the ethernet bridge to eliminate having to plug it directly into a computer or other transport, and it allows me to access my entire music library that won't fit on my MacBook or iPhone.

However, the bridge is wired and it also requires additional software like JR Music server and JR Music Player iPhone App to control it. And unfortunately the Mac OS X version of the JR Music server was crashing so much at the time that I quit using the Bridge completely as soon as I received the D2 two years ago. It's that good.

With the D2 I am able to leave the transmitter plugged into my iMac 24/7, with iTunes running as a music server, and I can use the iPhone Remote app to control my music playing through my D2 > Eddie Current ZDT amplifier whenever I want. We already leave the iMac running to serve music and movies to all our Macs and Apple TV, because with five of us in the family we can easily exceed the 1TB Comcast bandwidth limit when streaming via the cloud - so we stream everything from the iMac instead.

Screenshot 2017-08-23 22.59.20.png

We never use the iMac for anything that requires the built-in speakers, so we leave the output set for the USB with the D2 DAC. I have a VNC app on my iPhone 7+ and iPad Air, in case someone does switch the iMac output to the internal speakers and I need to remotely switch it back to use the D2 for audio.

The Audioengine D2 is a 2-piece wireless DAC which has a separate transmitter and receiver that work on their own 2.4Ghz WiFi channel, but doesn't require a WiFi network to communicate. The audio is transmitted losslessly at up to 24/96 bit rates. The transmitter can be powered by USB, or by the 6V power brick that ships with it. My son told me the iPhone camera connection kit isn't powerful enough to run the transmitter's USB section, even when the D2 is plugged into it's power brick that apparently only powers the transmitter radio. The SPDIF receiver/DAC section is powered by the 6V 1000ma power brick only.

The Transmitter has USB audio and optical SPDIF inputs, so it can also be used with a standalone CD/DVD/BD player or HDTV that has an optical output. And the receiver has a optical output and analog RCA analog output, with decoding done by an internal AK4396 DAC (if I recall correctly, which when properly implemented can result in excellent sound).

The D2 can also be used solely as a USB to SPDIF converter, or as an optical SPDIF wireless transmitter, yet it also includes a nice DAC in case you don't have another DAC to use with it. This is similar to how we previously used our several Apple Airport Express units, which I also compared to the D2 DAC for feeding optical into my Perfectwave DAC Mk2.

The transmitter also has an output level control, so that if you are sitting at the source and playing through a remote amplifier across the room/house you can control the volume at the source without getting up. Both units have a "power" button and a "pair" button, and you can have multiple units in the house working with different sources and amplifiers, depending on how you pair them. They are small and about the size of 2-3 stacked CD cases each.

(1) My first comparison of the D2 was vs my CEntrance DACmini that I use in the bedroom daily with my MacBook Pro. The DACmini previously beat out my old PS Audio Digital Link III, as well as my well respected Stello DA100 and Apogee MiniDAC. I parted with the previous DACs because the CEntrance seemed to offer the micro-detail of the Apogee, plus the refinement and larger soundstage of the Stello, but without the jitter of the Digital Link III when used with some lesser transports (like 1st Gen Airport Express and 1st Gen Apple TV).

In this comparison of the D2 vs the well known DACmini, I tested each as a DAC-only, with USB and optical sources, feeding their RCA outputs (with ALO Audio SXT cables) into my Edie Current ZDT amplifier, as well as using the DACmini's built-in amplifier. And I used a variety of headphones, including Sennheiser HD600 and HD800, HiFiman HE-560 and Edition X, Grado HF-2, and Audeze LCD-2 V2.

Note regarding synergy of the gear tested - the ZDT amplifier pairs much better than the DACmini with the HD800 and Grado HF-2 headphones, making the choice of DAC less important when using this amp with those phones. It was actually harder to tell the difference between DACs when using the ZDT amp, while the DACmini's amp was less forgiving with different DACs and headphones, and could become a little more edgy with certain music played through these two headphones. So, remember that your amp and headphone choices can definitely affect how much you enjoy the D2 DAC.

Regardless, with my MacBook Pro via USB or optical output, the Audioengine D2's RCA output was basically almost indistinguishable from my $800 DACmini DAC in most areas, including excellent frequency response, extension, speed, micro-detail, ambience, air, and space. The sound is quite neutral with little flavor of it's own, just like the DACmini,

I would not call either DAC overly analytical or sterile, although neither one is particularly smooth and warm either - just neutral, crisp and detailed. While I can't get into the detailed descriptions of the DAC + Amp + phones with specific songs, this far out from the worsening of my tinnitus after my first review, I do vividly recall how closely these two DACs performed side by side.

So, if you've heard the DACmini for yourself then you have a better idea of how this DAC might also sound. If you thought that the DACmini was too bright (unless used with a warm amp), then this might not be the DAC for you either.

Nevertheless, while quite open and transparent sounding, in some instances (especially with the DACmini's built-in amp) I thought the DACmini's DAC was slightly less analytical than the D2, although neither one was as warm, smooth, and romantic sounding as my old Stello DA100 or my current Perfectwave DAC (PWD). This was the same result whether feeding the D2 RCA or optical outputs into the DACmini (to use its amplifier), although less so when feeding them into the ZDT amp which was more forgiving as noted below.

(2) Switching these two DACs to directly feed my Eddie Current ZDT amplifier (using ALO Audio SXT RCA cables) improved the sound noticeably, with more bass impact and warmth, giving the instruments more body and presence. Ambience and Imaging were surprisingly good using these two DACs via the DACmini amp, but they improved even more with the ZDT amplifier. Basically the D2 scales up when you upgrade your amplifier ($3,000 maxed out ZDT). There is very good synergy using both of these DACs with my ZDT amplifier, and as noted before, the differences in the D2 and DACmini as a DAC-only are smaller with a better amp like the ZDT.

(3) As I only had one set of the ALO Audio SXT RCA cables and I wanted to do some A/B testing, I tried each DAC with these, as well as using a pair of Anti-Cables RCA interconnects. I performed an A/B comparison with one DAC connected to the ZDT's input #1 and the other DAC on input #2. The differences the cables made was negligible on the sound differences between the two DACs, and my impressions remained the same.

(4) And as I mentioned, I'm currently using the D2 paired directly with my ZDT amplifier, bypassing my Perfectwave DAC altogether unless I'm sitting on the couch with my MacBook right there to plug into the PWD. The ZDT is less picky about what DAC I use, so the D2 > ZDT is perfect to casually listen while controlling my music playback with my iPhone.

So, in my next comparison I set out to explore the quality of the D2 analog output vs my old 1st Gen Airport Express for wireless audio, while connected directly to the ZDT amp. I left the D2 receiver's analog outputs connected to the amp's RCA input #1, and added the Apple Airport Express analog output to the amp's input #2 (using my ALO Audio SXT mini-RCA interconnects).

Using Airplay to send music through the Airport Express analog output was a huge disappointment. There simply was no comparison to the excellent sound quality of the D2. The 1st Get Airport Express sounded dull and lifeless when compared the D2 analog output - with lack of sparkle, detail, extension, and soundstage.

It was worse than any Bluetooth wireless audio, and even the Audioengine B1 upsampling bluetooth DAC beats the crap out of the Airport Express (the B1 is actually quite good with my iPhone bluetooth, and may be better for those who prefer a warmer, punchier, and more euphonic or romantic sound.

(5) The next step was to test the D2 optical SPDIF output vs the Airport Express optical output. When I compared the D2 optical out vs the Airport Express optical out, feeding them into the Perfectwave DAC and then into the ZDT amp, the same differences were there. There was no doubt that Airport Express via optical out still sounded terrible in comparison to the D2, and I'm not sure it was any better than the Airport Express analog out. It's crazy how a bad optical source can make a $4,000 DAC sound bad.

Maybe the old Airport is fine for casual listening in a college student's apartment, but not by any definition would the 1st Gen Airport Express optical or analog output be close to "audiophile" quality. It's no wonder that I retired my Airport Express over 2 years ago.

I seem to recall a few years ago that the Apple TV 2nd/3rd generation optical output was much better than the optical output of the 1st Gen Airport Express or ATV, so I have to wonder if the 2nd Gen Airport Express is also better. Maybe I'll pick up a newer one to test it one of these days - it's too bad the 4th Gen ATV lost the optical output, because I do have one of those.

(6) And lastly, I compared the the Audioengine D2's RCA output to the it's own optical out. The D2's RCA and optical outputs operate simultaneously, making it easier to compare them. I connected the D2 RCA out to my ZDT amplifier input #1, and connected the Perfectwave DAC Mk2 RCA output to the amp's input #2. In this case I then connected the D2 optical out into the Perfectwave DAC, so that I could compare the D2 analog output directly vs the D2 optical output that was feeding a better DAC.

When switching between the ZDT input #1 and #2 (which was the D2 analog vs D2 optical) the sound was basically indistinguishable between inputs. I simply couldn't tell which input I was listening to, and the sound signature and quality of the RCA out and optical out were nearly identical, despite using the optical with the PWD. I don't know if the D2 optical out is limited by the design to sound the same as it's RCA output, but using the D2 optical into the PWD didn't result in any improvement over the already excellent sound out of the RCA jacks.

It was only when connecting my DVD player or Macbook Pro directly to the perfect wave DAC, via coax or optical with the same music, that I could hear a difference with the PWD. With the MacBook USB > PWD > ZDT having a little more air and ambience and depth of stage, and slightly fuller impact and weight to the instruments, one could again appreciate the more expensive DAC.

SUMMARY: The Audioengine D2 is a very nice sounding low to mid-level wireless DAC that rivals a wired DAC costing twice a much (albeit without a built-in amp). The RCA output is clean and crisp, and neutral or uncolored sounding, making most audiophiles content with the sound, especially vs using an Airport Express with Airplay. And if you want a slightly warmer sounding wireless DAC, with slightly less micro-detail and ambience, but more impact, punch, and warmth, then consider the Audioengine B1 wireless DAC with 24/96 upsampling. That is what I have connected to my ZDT amp's input #3 right now.

Based on what I heard, the main reason that I see to use the D2 optical output is when you want to listen to music wirelessly but your home theater receiver or headphone amp is out of available analog inputs. Otherwise you'll get a similar performance out the D2 RCA output, and can skip the step of having an extra DAC in the music's pathway.

Right now I have the D2 RCA output connected directly to one of the inputs on my ZDT amp, and I often I don't bother turning on the PWD for a quick listen that the D2 can handle nicely on its own. When I want the ultimate listening experience, then I'll use my MacBook Pro via the PWD USB or optical, or I use my CD player on the PWD coax input. I still use the B1 bluetooth DAC on input #3 with my iPhone or iPad which can't work with the D2.

I may someday go back to using the PWD ethernet bridge, but with the B1 and D2 I can can have 90% of the sound quality and control my music easily with my iPhone, without the trouble of upgrading my buggy JR Music player or buying some other DLNA/uPNP music controller to fetch music from my NAS and send it to the PWD via ethernet cable. I don't even have my PWD connected to ethernet anymore, after getting these wireless DACs.

The D2 comes with the transmitter and receiver, two power bricks, a USB cable, and a set of RCA cables, so you can get started using it right away.

Screenshot 2017-08-23 22.59.31.png

I want to thank Brady and Brett at Audiengine for the use of the D2 DAC, and apologize for taking so long to repost my review after it was lost.
Oct 12, 2017 at 5:03 AM Post #2 of 7


Headphoneus Supremus
Aug 18, 2007
Wow, not a single fox was given? Sad, because this DAC is quite good for the price, and the fact that it's wireless and supports Optical SPDIF and USB input at 24/96 is a bonus.

Interestingly, before Rocky Mountain Audio Fest last weekend I plugged my Perfectwave DAC back into ethernet, only to discover it had developed a high level of white noise on the ethernet bridge. So, I dropped it off with PS Audio for repair at their booth/room at RMAF, and I'm happily using my D2 and B1 DACs, as well as the RCA output of my Nuforce CD Player with memory buffer and re-clocking.

Its nice having 3 inputs to my ZDT amp, so I can choose between many sources. When the PWD DAC Mk2 comes back I'll disconnect the CD player from the ZDT amp, and go back to using the CD via coax input on PWD, but the B1 and D2 DACs will stay connected directly to the amp for wireless from the iMac or iPhone.
Jul 3, 2020 at 11:03 PM Post #4 of 7


Headphoneus Supremus
Aug 18, 2007
In the years since, are there better units out on the market?

Does aptX HD or LDAC come close to what this gear delivers?

I'm still extremely impressed with the D2 WiFi wireless DAC - I still have mine and my son also has one. We both keep our D2 receivers plugged into our Pioneer VSX-LX102 and VSX-LX303 home theater amps, since AirPlay does such a worse job in comparison. We currently use the D2 RCA output, since the optical out into the Pioneer AVR and using the Pioneer DAC is not better.

I don't think Bluetooth is quite there yet, but I have only ever used AAC and aptX, and not LDAC or aptX HD. A few devices are really good as a BT DAC, notably things like the CEntrance BlueDAC and HiFi M8 V2, or Audioengine B1 - I have not tried the others. CEntrance does it best, followed by Audioengine - both doing re-clocking and upsampling into a 24 bit AKM DAC. My Fiio BTR-5 is a little grainier and edgier in the highs, and less warm sounding at the same time.

I have the Audioengine B1 aptX and aptX HD Bluetooth DAC with upsampling and re-clocking, and both versions sound extremely good. But it doesn't have the deep level of resolution in the micro-details that the D2 has. The B1 is warmer and smoother sounding, with less micro-detail, but it has an extremely musical signature that is also forgiving of the poor program material that is often used with a budget Bluetooth rig (Spotify). With Tidal lossless or Apple Lossless Audio Codec music you can still hear a slight improvement in sound vs the same album that is only encoded in 256K AAC.

We have three B1 v1 (aptX no HD) PLUS two B1 v2 (aptX HD) in the house. We have some that are used with our Audioengine powered speakers (A2 and A5), and I also have one on my Eddie Current ZDT amp on the 3rd input, for casual listening wirelessly with my iPhone. Note - The 1st ZDT amp input is connected to my hi-res PS Audio Perfect Wave DAC Mk2, and the 2nd input is connected to my Nuforce CDP-100 buffered output CD player (reads the CD and the digital signal is buffered into a RAM cache, and then that is reclecked and fed into the DAC and finally thru the RCA out). The B1 is one of my favorite budget DACs for listening to my HD800 on a bright amp or tube (it takes the edge off).

However, the B1 even sounds fantastic via our iPhone 8+ and 11 Pro Max that only use AAC and don't support aptX. MacBook supports aptX but not aptX HD, so I can't say if HD sounds better, but it could be. I actually prefer iPhone Bluetooth via AAC into the B1 rather than via aptX on my MacBook - it sounds fuller and more lively out of the iPhone. Many sources claim that regular aptX is not as good as AAC which is a psychoacoustic compression CODEC and not a compressed lossy PCM codec. At least thru Apple gear, sticking with ACC Bluetooth might be a better choice. Bluetooth Explorer (part of Xcode tools) will let you force your MacBook to use only aptX or AAC and skip SBC when possible.

I'd say 95% of the people who want to casually use Bluetooth from a phone or laptop into their headphone or speaker amplifier would be very happy with the B1 (either version, early model or current model), and maybe even 75% of audiophiles would understand what it does and enjoy it. The rest would complain about wanting better treble presence and detail, which they would get from the D2.

What I have personally neglected to do is to compare the B1 RCA out to the B1 optical out going into a nicer DAC. I do know that optical out is not needed on the D2 for better sound vs the RCA, and it may be the same with the B1. In fact, my son has tried the B1 optical out into the D1 DAC, and he claims there was no difference in sound vs RCA out with a good cable (anti-cables $100), and he only did the optical out of the B1 into the D1 because his very early model of B1 had its RCA output die (quickly replaced under warranty, still runs years later).

Here is the technical spec data from Audioengine on the B1 DAC.

Bluetooth receiver type
Bluetooth 5.0 audio
Supported Bluetooth codecs
aptX HD, aptX low latency, aptX, AAC, SBC
Supported Bluetooth profiles
Stereo analog RCA
Digital optical (SPDIF)
Required power
5V, 200mA
Operation range
up to 100ft (30m) typical
Full-scale output
2.0V RMS
Output impedance
57 Ohms
D/A converter
AKM AK4396
Power filtering
3-stage redundant regulation
SNR (DC to 20 kHz)
(1 kHz FS 96 kS/s) <0.02%
Frequency response
10Hz – 20kHz (+/-0.5dB)
Input bit depth
24-bit (upsampled)
Input data rate
Determined by Bluetooth
~30 milliseconds (ms)
Product dimensions
3.5 x 4.0 x 1u201d
Shipping weight
1.0lbs (0.5kg)
Shipping box dimensions
11 x 7 x 3u2033
Environmental Requirements
Operating temperature: 32° to 105°F (0°C to 40°C)
Storage temperature: -4°0 to 115°F (-20°C to 46°C)
Relative humidity: 5% to 95% non-condensing
Included accessories
RCA audio cable (3ft/1m)
Power adapter with detachable cable
Microfiber bag
Setup guide
Technical Features
Supports all Bluetooth-enabled devices
High-fidelity Bluetooth with aptX transmission and extended range
Stream high-resolution 24-bit digital audio from the Audioengine B1 to any music system.
Includes built-in AKM4396 DAC for superior 24-bit upsampled playback
Aluminum case with audiophile-grade connectors
Analog and optical outputs
2.0Vrms maximum output level
Experience stunning audio quality with aptX HD coding, built-in 24-bit upsampling DAC, and extended wireless range.
DAC Characteristics
The B1 Bluetooth Receiver utilizes the AKM AK4396A DAC, widely known for its low noise and high fidelity. B1 is essentially an upsampling 24-bit Bluetooth DAC and will pad all bit depths internally to 24-bits, thus achieving a higher signal-to-noise ratio. Due to the AK4396A’s high signal-to-noise specs, the fact that the digital signal is converted (upsampled) to 24-bits and the added benefit of triple redundancy power source conversion and filtering, the B1 presents impressive low noise and low distortion characteristics with a noticeable improvement over other Bluetooth devices.
Extended Range
Most Bluetooth implementations have very limited range, usually within just one room. But with careful signal management circuitry and antenna tuning, we offer a superior solution that will reach more than one room with no degradation in audio quality.
High quality Bluetooth audio
The B1 features aptX HD coding which is an advanced Bluetooth audio codec that provides much higher-quality sound than previous versions. The B1 is backwards-compatible with all previous Bluetooth implementations as well, so you can wirelessly stream music from any device and still enjoy outstanding sound.
Optical Output
B1 also functions as a wireless audio bridge from your device to your favorite DAC or preamp. Use the internal DAC with RCA analog outputs or connect the optical output into another DAC.
Jul 3, 2020 at 11:35 PM Post #5 of 7


Jun 26, 2020
Wow talk about a response, above and beyond, thanks so much!

I do not understand this
I have only ever used AAC and aptX, and not LDAC or aptX HD

Since you have so many devices that are compatible with those codecs, certainly HD on both ends.

I don't do iFruit, so maybe that's why?

For now I'm not worried about the DAC quality so much, so just looking at the BT transport, with analog inputs at both sides,

I interpret your above as, the cost premium of the D2 over B1 may not be worth it?
Jul 4, 2020 at 1:35 AM Post #7 of 7


Headphoneus Supremus
Aug 18, 2007
Wow talk about a response, above and beyond, thanks so much!

I do not understand this
HeadphoneAddict said:
I have only ever used AAC and aptX, and not LDAC or aptX HD

Since you have so many devices that are compatible with those codecs, certainly HD on both ends.

I don't do iFruit, so maybe that's why?

For now I'm not worried about the DAC quality so much, so just looking at the BT transport, with analog inputs at both sides,

I interpret your above as, the cost premium of the D2 over B1 may not be worth it?

(1) Yes, that is why. I am firmly embedded in the iFruit ecosystem. Since they only support AAC and SBC bluetooth on iPhones, and AAC, aptX, or SBC on Macs, I have never been able to try LDAC or aptX on anything. I did get to try SDHC via the HiFiMan App into the Bluetooth R2R2000 DAP (a variant of LDHC hi-res BT) but that was killed, and it's only other codec is SBC and it's now not as good as the CEntrance BlueDAC.

(2) Both the D2 and B1 have analog outputs, but not "...with analog inputs at both sides" as you mentioned above. Their input is either USB + optical for the D2, or Bluetooth input only for the B1 -> with analog RCA and optical digital outputs for both the D2 and B1.

(3) As for the "cost premium", If you are just looking to get pretty good wireless audio out of your phone or computer, and you don't need "audiophile grade" gear, the B1 is very good at a significantly lower cost and will probably make you happy.

And should I infer, the answer to this

> In the years since, are there better units out on the market?

is No?

At first you asked about Bluetooth, i.e. is it there yet? I mentioned that has better Bluetooth performance from their BlueDAC or the new HiFi M8 V2, but that is at 2-4x the cost of the B1 (I have the M8 V2 review sample, and I also paid in pre-order). The BlueDAC is not currently in production, so I didn't go into details, but they sold for $399 vs $189 for the B1.

The M8 V2 is also noticeably better at Bluetooth wireless than the B1, and it's a BT and USB DAC/Amp that's like $750 which will be shipping in a couple of weeks. However, while it's BT is also better than the B1, where it really shines with with the USB DAC and balanced headphone amplifier. You could use a CEntrance DAC/amp like a B1 to feed wireless audio into another amp out of the single ended or balanced headphone outputs, using the BlueDAC or M8 V2 as a "preamplifier" since the output is so clean.

As for just good wireless, BT or something else, I was also impressed with Bluenote's gear at Rocky Mountain Audio Fest, such as the Node and PowerNode But I am not well versed in how they operate, so I can't tell you how they are actually used (apps, media storage, etc).

Since I have been so happy with the D2 as an audiophile wireless solution, I stopped looking for an upgrade to AirPlay wireless playback. Airplay via my original Airport Express and the newer Airport Express both had noticeably worse analog or optical output quality than the B1 or D2.
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