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Reviewer: Paul Candy
Source: Cairn Fog v2.0 24/192 CD player, Audio Zone DAC [in for review], Stello CDT200 CD transport [in for review], Pro-Ject 2 Xperience turntable w/ Nagaoka MP30 cartridge [in for review], Pro-Ject 1 Xpression turntable w/AT95E cartridge
Preamp/Integrated: Manley Labs Stingray, Audio Zone AMP-1, Stello DP200 DAC/preamp [in for review], Pro-Ject Tube Box phono stage, Graham Slee Era Gold Mk V and Gram Amp-2 SE phono stages [in for review]
Amp: Stello M200 mono amps [in for review]
Speakers: Meadowlark Kestrel 2.
Cables: DH Labs Revelation interconnects, Q-10 speaker cables, D-75 BNC digital cable, and Power Plus AC cables, Audience Maestro interconnects, speaker cables and powerChord AC cables, GutWire Power Clef 2, Power Clef SE AC cables, Audio Magic Illusion 4D AC cable.
Stands: Premier three-tier, filled with sand.
Powerline conditioning: Audio Magic Stealth XXX [in for review]
Sundry accessories: Pro-Ject Speed Box, Pro-Ject Speed Box SE [in for review], Gingko Audio Cloud 11 platform, Grand Prix Audio APEX footers, Walker Audio SST contact enhancer, Audience Auric Illuminator MkII, GutWire Notepads and SoundPads, Duende Criatura Tube Rings, AudioPrism Isobearings, dedicated AC line with Isoclean ICP-002 outlet, homebrew acoustic treatments.
Room size: 13x17x8.
Review Component Retail: $795

Sometimes it must seem that I am on the Audio Zone payroll. I continue to heap praise on their products. However, I can assure conspiracy theory obsessed types that there's no shifty/shilly chicanery, payola or sneaky shenanigans involved. It's just that I continue to be impressed if not amazed with Audio Zone's ability to extract so much musicality and emotional involvement out of so few parts - and at such reasonable prices. AZ's Peter Daniel and George Tordai take minimalism to about as minimal as you can get. Just look at the innards -- or lack thereof -- of the AMP-1 or the subject of today's brief follow-up, the Audio Zone DAC. From what I understand of current digital-to-analog conversion methodology, this thing should not even work - or it should at least sound like a train derailing. However, it does not. Sure, I can pick out one or two faults in terms of sound but for shear music making on a budget, there is definitely something going on here. I find more enjoyment with the AZ DAC than with many other more expensive CD players and DACs.

Apart from one or two sonic concerns, I was mightily impressed with Audio Zone's new filter-less DAC during my first go-around with it. Nevertheless, AZ's Peter Daniel believed he could get more out of this design and recently sent me the tweaked and final production version to compare with the original late prototype. As you can see in the photos, the basic ingredients remain the same. The changes involved replacing or removing various caps and resistors. Now, there's even fewer parts!

Before I go any further, perhaps a brief primer on digital filtering is in order. According to the vast majority of the audio industry, accurate Redbook 16-bit/44.1kHz playback requires some sort of filter to attenuate if not completely eliminate mirror images that result from the D-to-A conversion process. These reflections occur on either side of the 44.1kHz sample rate and its harmonics. Supposedly, these spurious images, if left untouched, may cause very audible colorations and distortion, not to mention a great deal of difficulty for certain partnering amplifiers and loudspeaker tweeters. Incidentally, techniques such as oversampling and upsampling are extremely helpful tools in suppressing this digital noise. They push this racket into ultrasonic frequencies to allow shallower, less aggressive reconstruction filtering. Or so the theory goes. A small minority believes that these filters are less than desirable for audio use. The effectiveness of the filtering action is linked to a ringing on both sides of the impulse peak of each 16-bit sample. Apparently, it is this pre and post echo or ringing bracketing the signal's impulse that is cause for concern since half of it occurs actually prior to the musical event. Unfortunately, the degree of echo is directly proportional to the effectiveness of the digital filter, i.e. the more effective the filter is in reducing reflections, the more ringing will occur. Naysayers of conventional filters believe this pre-echo smears the signal in the time domain to adversely affect imaging and more importantly, rhythm or pace.

This is interesting. I find Redbook gear in general to be more or less lacking in the foot-tapping department when compared to vinyl. By removing the digital filter altogether; the impulse response is essentially perfect, without pre or post ringing. However, digital mirror images are free to run amok. This may cause audible (and certainly does cause very measurable) colorations. Some proponents of this topology such as Zanden use proprietary analog filters after the D-to-A process to attenuate this spuriae but that approach is very costly and will probably not trickle anytime soon into more budget-orientated products. Whether one chooses a filtered or non-filtered design will likely involve accepting distortion of one kind or another. Neither process is perfect but then, what else in life ever is? You just need to pick what's right for you. However, while the great majority of manufacturers believe suppression of spurious digital images is of paramount importance, it is interesting to note that some clever souls utilize additional circuitry alongside their oversampling digital filters in an attempt to reduce pre and post ringing. The filters used in Pioneer's Legato Link players are one example. Perhaps this ringing distortion is important to address after all.

During my brief period of comparing both prototype and production DACs, I listened to a handful of current re-releases that have been getting plenty of airtime recently: Martin Denny's quirky yet mesmerizing Quiet Village/Enchanted Sea two'fer [Scamp 9715]; Michael Tilson-Thomas' outstanding Symphonie Fantastique by Berlioz [RCA 60859]; Buddy Holly's self-titled disc [Geffen 159202] and The Replacements' garage classic, Let It Be [Restless 73761].

Music playback via the newer DAC was noticeably more dimensional, with a sense of greater information retrieval. Otherwise, the sonic landscape was identical. I should point out that comparing it against other digital components was tricky - the AZ DAC inverts absolute polarity. For meaningful A/B comparisons, the + and - leads of speaker cables required reversing. In my original review, I was not aware of the polarity inversion and now believe most of my negative comments may have been a result thereof. With incorrect polarity, I noted a softer, more closed-in and somewhat opaque presentation. Reversing my speaker leads for correct polarity offered greater ambient and spatial detail. Still, the newer model did offer a more vibrant and open presentation. Therefore, the revised DAC is more successful at playing music than the prototype was. Those two or three sonic concerns I noted are for the most part gone. Sure, I hear a little more air and sharper imaging with the twice as expensive Cairn Fog and Stello DP220, but neither is as fun, relaxing and thoroughly enjoyable as the Audio Zone DAC. If you are at all interested in trying a filter-less DAC, I cannot think of a better place to start - and not for a lot of money either.

With respect to the oft-claimed need for effective digital filtering, I have used AZ's filter-less DAC and the Scott-Nixon TubeDAC+ with several amplifiers and loudspeakers and never noticed any distortion that impeded my ability to enjoy music. Perhaps these unsuppressed images were partially or wholly responsible for the warm, slightly opaque yet relaxed, easy-going nature of these DACs? This all sounds suspiciously familiar to the oft-heard argument made by solid-state proponents. They claim that tube-based amplifiers measure terribly and are therefore ill suited for true high-end audio. As many audiophiles know, this is hardly true at all. Perhaps, the industry is measuring the wrong criteria. Do I care? More importantly, should you care? Like tube amps, the AZ DAC does seem to get the beat and natural flow of music right. Therefore, my original verdict still stands: if you get off on HiFi fireworks, you might prefer one of the current mainstream digital number crunchers. However, if you are in search of those long-gone days in your innocent youth when all that mattered was being able to appreciate a song's lyrics, its melody and its ability to capture your imagination... then the Audio Zone DAC might help.

I remain impressed with Audio Zone's entry into the digital field and recommend this product for those who are interested in trying a relatively inexpensive filter-less DAC. The AZ DAC gives you a glimpse of an alternative digital architecture at a considerably lower price. It really doesn't sound anything like most conventional designs. Just be careful of quick A/B comparisons. Let it break in for a couple of weeks, judge it on its own merit and prepare to be pleasantly surprised. I was.
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