Part One: Simplicity
There isn't a simpler computer audio component on the market today than the Halide Design DAC HD. The simplicity starts at the product research phase of one's purchase and ends with connecting the DAC to one's components. The DAC HD is like the other Halide Design products in that it's an all in one design. Attached to the DAC HD is a USB cable on one end and RCA analog output cables on the other end. Potential customers researching a DAC don't have to consider what cabling to use with the DAC HD. Halide Design has selected these components and made them captive in the design. Music aficionados seeking simplicity needn't look any further than the DAC HD. The USB end of the DAC connects to one's computer while the RCA analog outputs connects to one's preamplifier. There isn't even a power cable to mess with or upgrade in typical audiophile fashion. This simplistic design is great for traditional audio system as well as portable audio. I used the DAC HD in my Spectral Audio / TAD system and a little travel system in combination with headphones and a Ray Samuels Audio SR-71A battery powered headphone amp. The Halide DAC HD is at home in either retype of system.
Readers seeking a simple component like the DAC HD will likely want a simple run through of what makes this little devil sing. Starting on one end is a custom black Wire World Starlight USB cable. This cable is attached to the nicely finished anodized aluminum housing. Inside this tiny enclosure is a terrific design centering around the Wolfson WM8716 DAC chip, filtered and down regulated power rails, and a much lauded Streamlength® asynchronous USB enabled receiving chip capable of 24 bit / 96 kHz high resolution audio. The circuit board inside the enclosure fills almost the entire space, containing audio on one side and dedicating the other side to power. Out the other end of the enclosure are two silver analog cables terminated with Eichmann silver bullet RCA connectors. What's more, the entire product is cryogenically treated for your listening pleasure.
I listened to the DAC HD in two audio systems with several sources including Windows, OS X, and Linux based servers. I attempted to connect the new iPad (3rd generation) to the DAC HD using the camera connector kit but was unable to output an audio signal. Apple has stuck with its decision to limit the power output of the iPad to a level lower than required by most USB DACs. Upon connection to the DAC HD my iPad displayed the following message, "Cannot Use Device The connected USB device requires too much power." [Image] I'm sure it's possible to finagle the iPad and a power hungry DAC into working with a powered USB hub or similar, but that defeats the purpose of a simple design and the aesthetics of such an elegant solution.
The Halide Design DAC HD doesn't require installation of any software or device drivers to function at all supported sample rates. Simply plug the unit into a Mac or Windows computer, select the DAC within the playback application, and start listening to music. Using Linux servers like the Aurender and SOtM sMS-1000 the DAC HD just works. There's no selection or configuration to be made. Simply plug it in and select play. The DAC HD is capable of turning one's audio system into a toaster-like system when used with Linux servers. When I put bread in my toaster I get toasted bread every time without a doubt and without user intervention. When connecting the DAC HD to the SOtM sMS-1000 it's possible to get music every time without configuration or user intervention. USB into the sMS-1000 and RCA into a preamp, that's it.
Listening through the Halide DAC HD was a bit weird at first. Not because of the sound quality but because it's such a simplistic looking device. In my main system I connected the DAC HD to my Spectral Audio DMC-30SS Series 2 preamp. Next to the DAC HD was a dCS Debussy and a Berkeley Audio Design Alpha DAC with Alpha USB. I'm used to looking at and listening through those two DACs that are much larger and carry much larger price tags. The DAC HD merely looks like a cable laying next to behemoth electronics. Like all good reviewers, and Lady Justice, I put on my blindfold to overcome any sighted bias so easily encountered in this situation. Only kidding. If anything the DAC HD should have been trounced by larger, more expensive, and better looking components but this was not the case. The DAC HD was not as good as my main DACs in all aspects but it was very competitive. I always compare components in for review with either the Alpha DAC or the Debussy or both as these are my reference DACs. Without a reference it's impossible for me to judge components with any kind of consistency. One of my favorite albums for both listening pleasure and component demonstrations is Ray LaMontagne and the Pariah Dogs' God Willin' and the Creek Don't Rise. It's really a treat when a favorite album is also an album that sounds spectacular. This album is great for listening to Ray's voice texture and delicacy as well as low level bass guitar control and note delineation. For the most part the Halide DAC HD sounded great on all aspects of this recording. Ray's voice on This Love Is Over had excellent air around it and the opening bass notes were all distinct, not one blob of deep tones like some DACs reproduce. The bass notes on the track Repo Man are also something to behold through a good system. I'm not talking monstrous low-rider 1969 Impala at a stop light bass, rather distinct bass notes with a great groove. Only good equipment can really reproduce these with clarity. The DAC HD is definitely in that category and fully capable of such performance. However, in order to achieve this performance I had to turn up the volume louder than I do when listening through my reference DACs. This lack of low level resolution is my only gripe with the DAC HD. The DAC HD as a whole has great resolution but not at the lowest levels. In a way this is similar to the Peachtree DAC·iT I reviewed in December 2011. Both DACs were god performers but not the best a low levels. Neither of these DACs is going to reproduce a hummingbird's cough a extremely low levels, but neither DAC is built as a reference piece to reproduce such infinitesimal nuances. Some great tracks that brought out the best in the DAC HD were from Ottmar Liebert's One Guitar in high resolution 24/96. This solo acoustic performance sounds spectacular with an awesome sense of space around Ottmar and decay on his guitar notes. The DAC HD connected to my MacBook Pro and SR-71A headphone amp with Etymotic ER4-P earphones reproduced these aspects of the recording wonderfully. There something about well reproduced decay that really gets me going and into a recording like none other. Decay is a must when shooting for realism in reproduced music. Sense of space and decay were also wonderfully reproduced, albeit at higher volumes and in my main system, when listening to Martin Vatter's Walchensee, Mondnacht from the album Klangbilder I in high resolution 24/88.2. This album was recorded at Bauer Studios in Ludwigsburg by Mbl Engineer Juergen Reis. Juergen recorded it live to two track without the use of compressors, limiters, overdubs, or cuts of any kind. He recently remasterd the album for release as a 24/88.2 download with its original dynamic range score of DR13. I first heard this track at the Mbl suite in Las Vegas for CES 2012. Playing it in my own system was a little less dramatic as it was on the Mbl 101 Extreme system, but the emotion and realism brought out by the piano was still wonderful. The Halide DAC HD did a great job reproducing the decay in this recording.
In my main and portable systems, on Windows, OS X, and Linux operating systems the Halide DAC HD performed great. The DAC HD worked every time without fiddling. This DAC is not a tweaker's delight, rather it can be viewed as a system. Take the USB cable, DAC, and analog cables as a whole or keep shopping as this DAC might not be a perfect fit for everyone. Audiophiles looking for that "works every time" and plug n' play type of product will likely find comfort in the Halide Design DAC HD.
Part Two: Complexity
Computer audiophiles shouldn't let the DAC HD's simplicity of use and external design fool them into thinking it's a simplistic little device. One mark of a great design is hiding complexity behind simplicity and leading end users to believe there isn't much to the actual product. I'm willing to bet most people don't think or don't care to think that the Apple TV is a complex computer. People use the Apple TV for simplicity that hides its complexity. The Halide DAC HD has a tremendous amount of engineering and talented design work inside its small housing. It may be hard to imagine but every internal component and adjustment from the DAC chip to the output stage, capacitors, power supply, and cabling has been judiciously engineered as if this was a traditional DAC that sits in an audiophile's rack. In fact, the silver mica capacitors used in the analog output filter stage alone cost Halide over $10. Anyone familiar with cost of materials multipliers will understand how much of an investment in caps Halide has made in the DAC HD.
Halide Design selected the Wollfson WM8716 as its DAC chip of choice. Many of the reasons this chip is so good for the DAC HD are related to power. For those keeping score at home the DAC HD contains 8 independent voltage regulators. The DAC HD is powered solely from the computer's USB bus that maxes out at 5v. The analog supply of the Wolfson WM8716 is run at 4.5v. Halide filters and down-regulates the incoming power signal and minimizes the current draw on the negative power rail. According to Halide Design less is better when it comes to things powered by this negative rail. The DAC HD powers only one op-amp per channel on the negative rail to lower switching noise caused by DC-DC conversion. The final product of this and much more engineering is a lower jitter output.
In a recent conversion Halide Design's Jonathan Driscoll talked to me about the DAC HD's output stage and the interrelation of each component. One issue with delta-sigma converters like the Wolfson WM8716 is a large amount of switching noise on the output. This noise is clearly visible as a fuzzy waveform when looking at the output on a scope. Thus fuzz is caused by high frequency garbage as it's call by engineers. According to Driscoll, "It's a (common) mistake to think you can just throw the output from a DAC like this straight across an op-amp and have things work out. Op-amps are fundamentally, by design, frequency limited, and the switching noise pushes them far outside of their operating limits. This should be obvious, and yet right in the datasheets of many delta-sigma DACs there is an op-amp for the output stage, with no filtering. It's just plain wrong, and probably a big part of why people use discrete circuits instead." It's very evident that the DAC HD is much more than the sum of its parts. Assembling the components according to data sheets would have lead to a clearly inferior design.
Back to the Wolfson WM8716 and the interrelation between components. One benefit of the WM8716 is its onboard lowpass filter. This filter removes much of the aforementioned switching noise before it leaves the Wolfson chip. Another benefit of this WM8716 is it supply of voltage out rather than current out. This allows the routing of the signal directly into a filter prior to any active, bandwidth limited electronics. Halide takes this one step further with an extra filter capacitor before the op-amp sees the signal and a capacitor in the feedback path to make the filter a two pole Butterworth design. Halide uses silver-mica caps for the output stage filtering, because of their unique combination of extremely high linearity and simultaneous ability to handle the high frequencies from the switching noise. Working with frequencies up to 10 mHz in addition to the audio band is not easy for a capacitor to do and remain linear throughout the entire range. Silver-mica caps perform excellent under these circumstances, but don't come cheap.
Halide Design elected to use a Wire World Starlight as part of the DAC HD over the generic USB cable used with its other products. The most compelling feature of the Wire World cable, according to Halide, is the coaxial power line that's completely shielded from the data line. In addition due to the thick gauge wire Halide supports up to a seven meter USB cable without problems pushing current to the DAC.
A very popular topic when discussing USB interfaces is the use of galvanic isolation between the computer and audio component. I specifically asked Halide about isolation and what is done in the DAC HD. The answer was compelling and will certainly stir the pot. "People have different ideas about this. We didn't do it on the HD." said Driscoll. Instead of stopping there he went on to present solid information as to why isolation isn't always the silver bullet. "We've actually built isolation DACs before, but you have to be careful when you do this. For one, you have to send the power across a transformer to isolate it as well, which typically means adding a lot of switch noise. This can then trickle out to the clock power supply, causing jitter, or simply appear directly on the output." Driscoll went on to say, "The other odd thing is that you actually open yourself up to a certain kind of noise - if your two ground planes are at a different potentials, this can create a strong electric field between the two, and actually generate 60 Hz hum." Halide was quick to not criticize manufacturers who support isolation as there are ways of doing it right. "Also, in a much larger chassis one doesn't need to worry as much about stray fields" said Driscoll.
Yes that's ultra geeky stuff, but this is the complex section of the review. Additional information about the DAC HD design can be found on the Halide Design DAC HD product pages. Of note is Halide's reasoning for not publishing jitter specifications. I agree with Halide's position 100% and recommend everyone read it for themselves [Link].
Complexity hidden behind a wall of simplicity is a good way to think of the Halide Design DAC HD. Computer audiophiles seeking the simplest of solutions to get music from a computer to their audio system needn't look further. The DAC HD works every time with every popular operating system including many plug n' play music servers like the Aurender S10 and SOtM sMS-1000. There are no USB or RCA cables to purchase either. This not only simplifies the purchasing decision but may save users money depending on one's level of audiophile neurosis. For others who like to tweak things a bit this type of all-in-one solution is not a solution. As long as potential customers know this going in there should be no surprises. The high level of engineering hidden behind this simplistic approach is enough to surprise many audiophiles. It's hard to believe so much can be done in a 1.875 cubic inch package. All of the engineering has paid off for Halide. In addition licensing Streamlength asynchronous USB code was a smart decision. The end result is a product that is at home in a full blown audiophile system as well as a portable setup capable of a million miles per year. The sound quality output from the DAC HD is great. It's very similar to one of my category favorites the Peachtree DAC·iT. Both DACs require a little volume to bring out the best, but when it comes to volume a little more is almost always better. The DAC HD is another great product from the team at Halide Design. Simple and complex for those who desire both or just simple For Those About To Rock.
- Product - Halide Design DAC HD
- Price - $550
- Product Page - Link
- Product Details - Link
- Where To Buy - Online Store
- Source: Aurender S10, C.A.P.S. v2.0 Server, MacBook Pro, SOtM sMS-1000
- DAC: Berkeley Audio Design Alpha DAC Series 2, dCS Debussy
- Preamp: Spectral Audio DMC-30SS Series 2
- Amplifier: Spectral Audio DMA-260
- Loudspeakers: TAD Labs CR1 Compact Reference
- Remote Control Software: Aurender iPad App, JRemote, MPaD
- Remote Control Hardware: iPhone 4, iPad
- Playback Software Windows 7: J River Media Center 17
- Playback Software: Mac OS X 10.7.x, Pure Music
- Cables: Spectral Audio MH-770 Ultralinear CVTerminator Series II Loudspeaker Cable, Spectral Audio MI-350 Ultralinear CVTerminator Series II Analog Interconnects (RCA), Mogami W3173 Heavy Duty AES 110 ?, MIT Oracle ZIII Power Cables, Wire World Silver Starlight USB Cable, AudioQuest Diamond USB Cable, Kimber Kable B Bus Ag USB Cable, WireWorld Ultraviolet 5 S/PDIF Coax Cable (BNC), Baaske MI-1005 Ethernet Isolator, Micro Connectors Augmented Cat6A Ethernet Cable