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Hawk Audio MP-DAC kit

[Italian version]

Product: Hawk Audio MP-DAC
Manufacturer: APN / Audio & Techniek, UK distributor
Approximate price: 1160EU (built) / 775EU (complete kit) / 615EU (without housing and bits)
Test sample: loaned from manufacturer
Reviewer: Werner Ogiers

Dead trees and audio

Audiophile Products Netherlands (APN) aka Audio Research Center (ARC) aka Audio & Techniek aka Audio & Muziek: a lot of names for what essentially is/was/will-be the publisher of Holland's most willful, most interesting, audio magazine ever.

In commercial terms a pretty unsuccessful magazine, but, linked to this, also a pretty good magazine. Essentially a bunch of audio and electronics engineers part-time performing as journalist (among them Peter Van Willenswaard, who once in a while appears in Stereophile, and IMHO still one of the best audio reviewers walking this planet). Concentrating on the basics, and therefore - uh - with a shoddy mag layout, with black and white pictures, even with bad typography, all in a charming atmosphere of amaturism (remember your Latin: that word stems from amare).

Oh, and with a rather critical stance. A very critical stance. A stance that would even scare the HP sauce from our own Thorsten's sauerkraut. Which is fine, as APN always backed their attacks on commercial audio components with a host of self-designed amplifier and speaker kits that one after the other got an enviable reputation for pure quality in the Benelux. Small wonder: which other audio magazine offers internships to engineering students to design a new component or to research some aspect of auditory perception?

Other mags talked specs, A&M told us that stereo was supposed to have depth, A&M told us that sound reproduction had to have musicality. Other mags hailed CD (it was 1985), A&M went to Sony/Philips/Akai and simply told them in the face that CD was crap. Not that this avoided the inevitable. The established magazines in the Benelux all reverted to a critiqueless babble, and A&M disappeared. Don't we all know such stories?

All that's left now are a website with the occasional interesting techno-article or component review. And the kits. Of course the kits. Since about a year now these kits are available world-wide, so time to take a closer look at them.

Personality crisis

Believe it or not, but APN-shaman John van der Sluis (interviewed by Lucio here) contacted me for a review of the MP-DAC right when I was considering buying his A-18 class-A zero-feedback amp kit.
And since right at that same time a Dynaco ST-35 valve amp crashed on our doorstep anyway - Christa almost tripping over it - the A-18 plans went into the fridge, and the digital-analogue convertor was sent in from Rotterdam.

Halfway the time alotted for this review, the product brand name was changed from APN to Hawk Audio. They couldn't resist, could they?

The machine

To the outside world the MP-DAC (Marco Pol DAC, referring to its designer, not to the Venetian explorer of post-medieval China) is a very simple device. No power switch, one coax digital input on BNC, and one set of analogue outputs. No reason to waste any more bandwidth/time/paper here.

The ghost in the machine

Conceptually this DAC's inner sanctum is very simple too: the digital stream arrives through a custom-made pulse transformer and a Crystal CS8412 input receiver, then is converted in a CS4390 DAC, followed by discrete analogue filter/amplifier section. That Crystal DAC chip is the same as is used in, for instance, Meridian's 508.24 CD-player. It is a delta-sigma (bitstream) device with a theoretical resolution of 24 bit, although in our world real 24 bit performance is beyond the possibilities of physics, unless time-averaging tricks like in the dCS RingDAC are employed, of course.

While the CS4390 features balanced-differential voltage outputs, the MP-DAC uses only one phase of the signal: this may compromise dynamics and internal common mode noise rejection, but allegedly the designers have tried all possible configurations of this chip, eventually settling for the solution with the best sonics.

The analogue section is curious in the sense that it is an adaptation of the A-18 power amp's voltage gain stage. So we are looking at a fully discrete, symmetrical, zero-loop-feedback class A amplifier, running off +/-30Vdc supplies, and with only two 2-transistor stages in the direct signal path (should something like a 'direct signal path' exist).

The filtering of out-of-band signals is done fifth-orderish, with a passive RCRCLC-section after the DAC chip, and a single RC filter at the output of the amplifier. All signal capacitors are nice polystyrene film-and-foils, bar one 3.3uF Audyn metallised polypropylene for coupling purposes.

With the DAC chip and its on-board voltage-output opamps a given, about the only thing one can do to coax better sonics from something like a Crystal CS4390 is to feed it a nice and clean supply voltage. Well, these APN guys are serious about their nutrition. Deadly serious: Two 30VA Amplimo toroids, one for the digital board inclusive the DAC, the other for the analogue board. Four rectifier bridges, damped with series resistors. Six series regulators (317s, 337s, 7812s and 7912s), and six TL431 shunt regulators. APN claim an ultra-high regulation bandwidth for the latter (which I find a bit dubious, as the bandwidth of a 431 operating with some gain is a mere 20kHz or so, but OK, kudos to APN for using these unusual devices which probably beat your average 317/337 every time of the day).
The overall capacitance reservoirs distributed over the whole DAC amount to 60000uF: that's more than my power amp can boast. Individual stages each have their own clusters of filter capacitors: big elcaps including Elna Stargets and Sanyo OS-CONs, Wima and Siemens polyester films, and then Sibatit ceramics for the highest frequencies. Before you go into a frenzy over all the possible parasitic resonances such contraptions can produce: the designer says he verified the real-life behaviour of these combinations.

No effort is done to minimise jitter, apart of course from feeding the digital circuits a clean voltage. The MP-DAC relies purely on the Crystal receiver's PLL to keep things in pace. For connections the APN people specify a decent coax, with BNC connectors, as RCAs "cause reflections due to mismatch". Which leaves me wondering about the mismatch caused by the solder terminals and the circuit board that coax is connected to? Never mind ...

From a technical point of view the MP-DAC is a very nice piece of work, something into which has gone a great deal of effort to optimise the analogue section and the power supplies. And both these aspects make it rather unique in a digital audio realm where tiny transformers, cheap IC opamps, and uninspired textbook "engineering" still are the norm.

The question

Now I can hear you mutter: What's the point in offering a DAC restricted to the standard 44.1k/16 CD format? Very easy question, although marketing droids and audio magazines, the villains, would want you believe otherwise.

There is no alternative format. Oh, 96kHz/24bit DACs do exist, and there is even the odd 192kHz compliant component out there. But there is no real consumer format available to benefit from these DACs. Take DAD, entirely embedded in DVD-Video. Yes, it is high-res audio. But not backed by the software community it will prove to be still-born, and further, the DVD players that really output a digital 96kHz stream on their S/PDIF port are 1) scarce (only Pioneer does this) and 2) quasi-illegal, as copy protection issues haven't been settled yet by the powers that be. In short: why bother?

The powers that be. They like a tough game. Competition's good for you. The powers that be. They pick horses for courses. They're the market forces. (Radio KAOS, Roger Waters. Who else?)

Then there are DVD-Audio, and of course renegades Philips' and Sony's SA-CD. Both hi-res. Again, both not legally enabling a full-resolution digital output stream. And if either of them, in the future, will have encrypted etcetera digital outputs, it will not be over the S/PDIF interface used by the DACs you can buy now. It will probably be over IEEE1394/Firewire, perhaps over USB or USB2. And believe me, the chances that DAC-vendors will offer retrofits to their older products are pretty slim: just look at the additional cost and complexity of, say, a full Firewire node.

The final source for high data rate audio is "upsampled" CD. If you believe in fairy tales, that is: what is lost remains lost. Otherwise we would have post-tax salary upsamplers (writing this from Belgium, with an over-50% ripoff, OK?). The only thing upsampling, itself just a fancy name for oversampling, buys you is that it enables you to use a new hi-speed DAC with a data rate slower than the one it was optimised for. And if that DAC happens to sound a little bit better, so then may your CDs. But I believe it is more a case of "different" than of "better"2: the upsampling process modifies the original data. It doesn't add information, and it changes, it has to change mutilate?), what there is. Hardly a valid option, but think of it, it does enable the high-end industry to sell you a few more boxes.

So, given the dearth of valid hi-res sources, and the abundance of ordinary CD software, there still seems to be a role for a 44.1kHz/16bit DAC. At least: for a good 44.1kHz/16bit DAC.

The ghost building the machine

Contrary to for instance the Parts Connection's Assemblage DAC kits, this one really is D-I-Y: you have to do everything, with as sole exception drilling out holes in the housing. So be prepared to stuff three PCBs with a couple of hundreds of components. Luckily these PCBs are very well made and of a good layout, with solder masks applied.
Still, given the overall complexity I would not advise this kit to anyone with only basic soldering and electronics skills. APN claim construction will need about 10 hours. I spent about 20 hours soldering, but then I took my time, and especially in the analogue sections I took care of hand-matching components for optimal channel balance. Problems? No serious ones: My 15W Ersa home iron was not quite powerful enough to do the three or four solder joints that are embedded in massive ground planes. I had to revert to Low Melting Point silver solder to get these correct.
If you have access to a temperature-controlled soldering station you'll fare better. (We have Weller stations at the lab, but I did not care for the paperwork required for checking-in the MP-DAC - in N loose parts - at said over-secured location: Nosir, this is an audio component, Sir, not part of a new superconducting computer I'm trying to steal, Sir.) Further the holes drilled for the Elna Starget caps in the analogue section were too small. Not wanting to re-drill, as this could have wiped away the throughplating, I just blue-tacked the Elnas to the PCB and directly soldered their leads to the top of the solder pads, SMD-style. A few holes on the power supply board were undersized as well, but this board is single-side and hence could safely be re-drilled. I understood from APN that a new version of the PSU board is shipping now.

While previous MP-DAC incarnations came in a grey 19" housing, looking a bit macho, and with undeniably a low domestic acceptance factor, the device tested here came in a custom black-lacquered 44-cm wide case which is a bit boring (heck, they initially forgot the copper name plaque!), but which matched my Michell gear well (must be the colour), while vaguely reminding me of Sphinx electronics. Funny: Sphinx is Dutch, and good-sounding, too. As for the fit and finish of this housing: the latter was excellent, and the former, well: suffice to say that it required a bit of creative input on my behalf to make it do what it was intended to do.

After the work, the fun

As you know, my regular CD-player is the Rega Planet. I bought one a couple of years ago, shortly after I wrote one of the very first published reviews of it for Audio Vision (in fact I think only What Hi-Fi beat us). I chose it because in a group test of similarly-priced players it was the only one to sound natural, as opposed to synthetic, and this without any trace of grain. Of course, the Planet isn't perfect. It tends to be a bit small-scale, and detail and air lack a mite, giving a vacuumed-background effect.
But these are small prices to pay for that naturality, especially at the Planet's low cost. And of course it behaves like a digital audio product: good discs can sound utterly wonderful, but all too often the sounds regenerated can be lacking in interest, in involvement. That's why the Planet is mostly used for background music, while the GyroDec is only used for serious listening. Serious, thus more fun.
Still, together with the Marantz CD-17 the Planet is one of the few CD-players I really like, and I found it to work nicely with preamps costing up to 3000EU.

Having finished the MP-DAC I switched it on, connected it, and verified that everything worked as it was supposed to do. It did. Knowing I shouldn't listen, I did. First impressions? This DAC instantly reminded me of the sound I got with my turntable and the Mistral Phonostage (reviewed here). But forget this, first impressions being what they are, I left the DAC on for a month, only using it for background music.

And it changed, during that month. David Sylvian's victorian jazz masterpiece Secrets of the Beehive betrayed the excellent low-level resolution of this DAC with subtle cymbals and natural, easy-to-follow decays, in a wide-enough and, above all, deep soundscape. That image depth is accentuated with vocals placed solidly in front of the speakers: placed forward, yes, but this in a gentle and relaxed way, as opposed to in-your-face.

Tonally the MP-DAC is off-a-piece, admirably consistent, merging a rolling and fruity bass with creamy mids and a truly sweet treble. Loreena McKennitt's The Visit can sometimes sound a bit thin, but not here! Likewise, my beloved Monteverdi recording of the Maria vespers (Archiv, Gardiner) never before sounded so believable, so complete, the choirs made up of almost-real people, singing in a really cavernous and complex acoustic that as a warm velvet cloak enveloped the listener (lucky me).

Positioning of sound sourced is a bit soft-focus, not as precise as modern transistor-based high-end amplifiers and CD-players tend to do. In addition, the texture of the sound was ever so slightly roughed-up, more like wood au naturel than, say, like polished steel. According to my experience both these characteristics tie in with the use of zero-feedback circuitry, and indeed the MP-DAC's sound resembles for instance the electronics of LFD/Mistral and the Kora amplifier I tested recently: all zero or low-feedback designs. And both these aspects should be contrasted to the more spot-lit, more sheeny, higher precision of conventional designs. Precision? Or apparent precision?

The amount of detail present, and especially the low-level resolution make this DAC emminently suited to late-night listening: even at feeble levels all of the music was still there, and this was the first time I could listen to the ethereal choir in Holst's Neptune without headphones, or without blowing up the speakers at the start of the subsequent - much louder - piece simply because the source demanded a ludicrously high listening level in order to help it pretend having anything like decent resolution. Well, the MP-DAC has it, resolution, and this makes things sound rather lifelike, be it the resin of Yo Yo Ma's cello (Insired By Bach - The Cello Suites), or the way the 'Cha cha cha' is sung by the backgrounders in Ruben Gonzalez' rendition of La Enganadora.

So all was well then? Of course not: perfection does not exist. Overall I found this DAC a little bit restrained. Perhaps because of a certain politeness during louder passages (then again, it did kick some ass with Hole, with the Walkabouts, and with the bass hammer in Tori Amos' Space Dog intro), or because of the warm, dare I say dark, tonal balance. However, to me this is not much of a problem: I'll take any time of the day a dark and musical component over a bright or neutral and overly analitical one. Moreover, one should not forget that this is a kit, and that it is an interesting property of kits that they can easily be tweaked (a just as interesting property of kit-builders of course being that they know how to do that tweaking bit), either by decreasing the action of the output filters, or by component substitution. But one shouldn't even go this far: substituting an ultra-short Deskadel interconnect (right, one of the few Belgian hifi products!) for the AN-V slightly opened-up things, whereas using a Marantz CD-52SE for transport gave the impression of a darker result, although here I could easily have been deceiving myself.

Conclusions

The MP-DAC is not a simple beginner's kit, and neither is it a particularly cheap one. But its sound is relaxed and warm, dynamically perhaps a bit polite or muted, but admirably consistent over the whole frequency spectrum, and with excellent low-level resolution and imaging.
So far this is one of most musical digital sources I have encountered. Furthermore, it is unfussy and should not pose much compatibility problems with other gear. Recommended.

© Copyright 2000 Werner Ogiers - http://www.tnt-audio.com

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