December 2001


The Tale of Two DACs Pt. 2
Audio Note Kit 1.2 Vs. ART's Highly Raved DI/O
Review by Steven R. Rochlin
Click here to e-mail reviewer

  It has been well over a year and a half since my last digital to analog converter (DAC) shootout. Back in February of 2000 it was the MSB Gold Link versus the Audio Note DAC Kit 1.1. Since that time both units have been subjected to various upgrades by the manufacture. Longstanding audiophiles realize that changes to DACs seem to go at a blinding pace. Not as fast as Intel releases processor chips though. This also may be why many people are playing the waiting game with DVD-Audio and SACD technology. Like computers, they get better and cheaper as time marches onward (and possibly waiting for more DVD-Audio/SACD software releases). In the end many of us have hundreds, if not thousands, of CDs and look for ways to enhance our musical enjoyment with our current music collection. Enter the Applied Research and Technology (ART) DI/O and Audio Note DAC Kit 1.2.

Enter ART's DI/O

Both units have had much brouhaha and virtual ink spilled praising them in various publications worldwide. The ART DI/O has been especially hot as the list price is only $249 while street price seem to hover in the $159 to $189 range. Unlike most digital to analog converts (DAC), the ART DI/O also has an analog to digital converter (ADC). This means you can hook up your turntable, cassette deck or other analog sources and have a digital output! This output is of the S/PDIF variety via industry standard RCA jack and impedance of 75 ohms. The data stream out is up to 24-bit/100kHz sampling rate! Digital decoding is of the 24-bit/96kHz variety though is user switchable for 44.1kHz, 48kHz88.2kHz or 96kHz. The DI/O has an "intelligent" external synchronization mode that will automatically sync to outboard gear from 22kHz to 100kHz. You want more from this $249 list price DAC?

How about adding a hand selected 12AX7 dual triode tube in the analog stage (for ADC duties)? ART calls this their "Tube Warmth" adjustment (right knob in image above) and is capable of being variably mixed in. Being like a volume control, you can set the Tube Warmth to either be turned all the way down as to not mix within the source signal, or variably added into the pure input source for an effect/mix of the tube stage. Furthermore this diminutive 5.25" x 5.375" x 2" (DxWxH) unit feels very solid and quite heavy given the small size. As seen below, everything is tightly packed into the main chassis. A well thought out curved cover simply wraps around the top and side of the unit and is held on by four screws.

Note below the two clear dots on the left circuit board. This probably insures the board does not touch the metal cover, yet as a side benefit it possibly assists in reducing the negative effects resonances can have as well. On the metal top cover (not shown here) there is also some cork-like material to keep the tube from vibrating against it. Quite an impressive and well though out design, yet also amazing given the $249 list price. Alas, all is not well in the Garden of Eden...

This unit is made for pro-sumer audio buffs and not audiophiles. Therefore all analog inputs and outputs are via monophonic 1/4" headphone jacks and not the typical home audio female RCA jacks (see image below) . This means that you will need to go out and get a female RCA to male 1/4" adapter. Popular parts supply store Radio Shack/Tandy sells such adapters for only a few dollars each. Of course it may not be "audiophile approved" to use adapters as the signal needs to go though more connections and therefore skews away from a purist viewpoint. While this issue can be ignored, some died-in-the-wool tweakers have craftily unsoldered the female 1/4" plugs on the DI/O and soldered in their chosen female RCA jack. Not an easy feat for an amateur as you can see in the above image, there really in not a whole heck of a lot of working room inside the DI/O. It has been suggested elsewhere to not have the female RCA jacks ground to the DI/O chassis as is usual with most audiophile gear. Instead, use insulation spacers so the female RCA jack does not touch the chassis (and therefore use the chassis as ground). Most high-quality RCA jacks offer these spacers so no real worries. There are also other matters to be dealt with...

The ART DI/O does not output the home audio industry standard 2 volts peak. Instead, it has 20dB of gain That equals 7 volts of output peak! While this may be great for those of us who use a purist stepped attenuator and can adjust accordingly, some active pre-amplifier might achieve input signal overload resulting in distorted sound output. Of course this is a small chance and i have as of yet to hear anyone who has experienced any overloading on input as of this writing. There is still a problem worth noting due to the DI/O high output. You see, a pre-amplifier's volume control attenuates (or amplifies) the signal with a certain set amount of adjustment. This means that your active pre-amplifier's volume control may really only allow music to be enjoyable from 0 to 20 on a normally achievable scale of 0 to 100 (100 being full volume output) due to achieving ear-splitting/lease breaking levels earlier than a normal 2 volt output unit. Still, and at only $250, all this underground raving and ranting has resulted in many audiophiles buying the ART DI/O who are making a go at it.

Lastly, the ART DI/O comes with a simple "wall wart" power supply rated at 1,3000mA. Many people have reported enhancing the audio performance of the DI/O by upgrading the aforementioned wall wart to a higher rated unit such as the Radio Shack/Tandy 3,4000mA power supply. Also beneficial seems to be in removing the vacuum tube. The exclusion of the tube allows for less signal interference and heat build-up within the unit while also allowing more power to be dedicated to the main DAC/ADC and solid-state analog output circuitry. Still, this unit has enough mystique surrounding it to be worthy of a reviewing by anyone within the high-end audio industry. Remember, even Adam ate the forbidden fruit given to him by Eve.

Enter Audio Note's DAC Kit 1.2

A company long known for finding unique and interesting ways to reproduce music, Audio Note has been integrating what many feel is old technology into their new designs. In fact Audio Note was selling single-ended tube amplifiers before the American reawakening almost eight years ago. Keep in mind that single-ended triode tube amplifier design can be dated back around eight decades ago! Their Audio Note DAC Kit 1.2 is much like that of the original DAC Kit 1.1 as reviewed here back in February 2000. Unlike the Art DI/O where you have a solid-state analog output, the Audio Note is strictly tube analog output. While the DAC Kit 1.1 employs the 12AU7A/ECC82 tube, the overall output impedance was in the range of 5,000 ohms. Some low input impedance pre-amplifiers did not quite achieve a match made in heaven. Audio Note decided to update the design, hence the DAC Kit 1.2 name, in July of 2001.

The new 1.2 version includes various enhancement to the original design. An upgraded power supply and new analog output circuit board was engaged to achieve an better, cleaner electrical power signal supply. Ausdio Note also rid the problematic BNC digital input of the version 1.1 and fits the 1.2 with a high-quality silver RCA jack. This allows the use of audiophile standard digital cables that have male RCA jacks on both ends. There is still an AES/EBU jack via XLR for those with professional audio gear. A toggle switch to the left of the RCA and XLR digital input jacks allows for ease of choosing between the two inputs (see image below). Improvements in the digital circuitry include the elimination of all ceramic bypass caps and the addition of polypropylene coupling caps on the digital inputs.

The main enhancement many people will find worthwhile is the use of a new analog stage. Instead of a single 12AU7A/ECC82 tube that achieved an output impedance in the neighborhood of 5,000 ohms, the Audio note DAC Kit 1.2 uses a 6DJ8/6922 dual triode to provide a more normal output impedance of 1,000 ohms. While still a touch on the high side of things, it is not overly high as to cause as many system matching/synergy problems as the 1.1 version did. Audio Note does offer an upgrade path for owners of the DAC Kit 1.1. Please note that unlike the cramp quarters of the DI/O, there is plenty of room to tweak and modify the 1.2.

As i wrote earlier, Audio Note tends to use old, sometimes "outdated" technology within their products. Like the DAC 5 Special reviews within these cyber pages in April of 2001, the DAC Kit 1.2 also uses "zero oversampling" technology. Within the 1.2 resides a Crystal CS8412CP input receiver and Analog Devices 18-bit AD1865N chip to support the digital stage. Unlike the DI/O that provides switchable 44.1/48/88.2/96kHz with a 128x oversampling digital stage, the 1.2 has no such provisions. In fact both units lack the ability to invert phasing for those recordings that may have been recorded with reverse phasing. This phase switch found on many DACs help to achieve a proper output signal as some recordings are in phase while others are out of phase. Lastly, the 1.2 has an output of three volts that is strong enough to drive purist stepped attenuators and will easily drive, without overloading, every active pre-amplifier that i know of. Please note that Peter Qvortrup wrote an essay concerning the use of 1x oversampling technology. Please click here to read.

DI/O Rocks The House 

First let me say that the ART DI/O sounds best with the tube out of the unit. Do not worry, the unit works fine without the tube in it. In fact it seems to sound better as there is no tube to use the much needed power for the other stages within the DI/O. Furthermore, a better power supply helps, though this will be covered later. Both units were run for a few hundred hours before being put though the paces. In fact there was some extensive listening sessions as the fast pace of review gear arriving at my door slows down (per my wishes). The music used to evaluate these two DACs include, but is not limited to, the wonderful new Chesky release Ana Caram Blue Bossa [JD219], JVC's smooth and silky XRCD Ella Fitzgerald and Joe Pass Take Love Easy [JVCXR-0031-2], Mapleshade's explosively dynamic and in your room Drink Small Electric Blues Doctor Live! [01832], Teldec Tchaikovsky 1812/Capriccio Italian/Swan Lake/Marche Slave [4509-90201-2] as it is the best combination of 1812 performance and recording quality i know of after trying well over twenty versions, and Mobile Fidelity's remarkable remaster of Pink Floyd The Wall [UDCD 2-537].

The DI/O has many different setting capabilities that control the way the digital signal is processed. One of the variables that seems to alter which setting may be best is the digital cable used. My tried and true Max Rochlin Memorial Cable was chosen for overall smoothness and synergy with the DI/O. Using the 44.1kHz setting yielded ok dynamics to this already lacking dynamics unit (in absolute terms) but also suffered from a slight loss in the midbass area. Moving the sampling up to 88.2kHz seemed to bring back the midbass yet lowered the overall dynamics plus it seemed to add some haze to the sound (read: less transparency). At 44.1kHz the highs also seemed more extended. Let me flatly state here that my ears did not like the 96kHz setting. External sync was also left off for best sound in my system.

Allow me to get right to the bottom line here, the DI/O is amazing for the money. For under $200 the thing is a modern day miracle. Substitute a Radio Shack 3,400mA power supply (some suggest reversing the polarity) or some other 3,000mA power supply instead of the stock version and the dynamics both micro and macro open up. Maybe not the best in ultimate terms, though vastly better than the stock supply. Remember to remove the vacuum tube as it sucks down power! Being a geek, there were many different power supplies here and i simply "dumpster dove" in my assorted box of mystery crap and used an old Sony power supply that went to something long forgotten. It is rated at 3,000mA. Fair enough. Alas, it is not my intention to try every one of the ?hundreds? of tweaks and parts upgrades suggested on various forums. Surely i am missing out on squeezing out every last drop of performance the DI/O may have to offer here, though as a reviewer i must also remember than not everyone may be willing to dive right in to that tight chassis with a soldering gun and go hog wild. Therefore all my impressions are with a stock unit with the exception of a better power supply (stock unit is only 1,300mA by the way, so my using a 3,000mA unit is definitely an upgrade).

In no-holds-barred, price-no-object terms the DI/O suffers from a lacking of overall smoothness yet does reproduce good imaging (if not effortlessly extending past the right of the right loudspeaker and past the left of the left loudspeaker). The DI/O with upgraded power supply has good dynamics too. While there still seemed to be a small amount of grey-like background and haze, the overal transparency is quite good for a unit at any price. Now before all you DI/O-heads e-mail me nasty letters of how this and that tweak will do "X" or "Y", please understand that i feel the DI/O is a real-world bargain in stock form with a small investment in a better power supply. Hence these other observations...

The DI/O has rock solid imagine between the speakers. Front soundscape depth and the ability the expand the soundscape completely into the room was lacking. Regardless, the performance offered up by the DI/O is simply better than some $3,000 DACs that were available only five years ago! Don't let the price fool you, this is a seriously good unit... shortcoming and all. The DI/O is simply superb and well worth an audition even if you currently use a 2+ year old $1,500 DAC. You may be in for a pleasant surprise! Please feel free to take the saved cash from buying a $500+ DAC and purchase more music for your collection.

On hard rock, progressive and industrial music the DI/O can keep up with the beat. It has a sound that agrees with hard and aggressive music. During such music as Chesky's Ana Caram Blue Bossa [JD219] or the psychedelic Mobile Fidelity Pink Floyd The Wall [UDCD 2-537] you seem to lose the finesse within the CD's pits and grooves. Mapleshade's Drink Small Electric Blues Doctor Live! [01832] was nicely portrayed through the DI/O. Drink Small's dynamics were a bit foreshortened and there was a slight lacking in transparent, yet it was enjoyable to listen to. Some of the very fine and low-level guitar work was hard to hear (or lost). Classical music was nicely reproduced as well, if lacking in some of the overall hall sound (air and space). Harmonically, this is the Achilles heel of the DI/O. This is not to say i want what some refer to as tube "lushness", just that as compared to live the music DI/O seems to strip away some of the intricate harmonics during massed acoustic instruments. In the end the DI/O is one of those things that somehow gets a lot right in overall scheme of things so long as you do not start to overanalyze things. Alas, that is my job to nit pick and write my feelings and thought here to you my friends. To protect and serve. By the way, JVC's XRCD Ella Fitzgerald and Joe Pass Take Love Easy [JVCXR-0031-2] sounded quite enjoyable on the DI/O. Just Ella and Joe in my room during a late night musical interlude.

An Audio Noteworthy DAC 1.2

Audio Note has long been known to make musically satisfying components, if having their own idiosyncrasies. The 1.2 is all Audio Note with the lack of any additional or extraneous features. There is no phase control, no sampling rate choices, no front on/off switch or front input selectivity. You simply hook up the necessary wires, make sure the rear input is correct, plug in the electrical cord and turn the rear power switch on. At least there is a front red LED to let you know the unit is powered on. (Said in good humor) Oh the luxury of a front red LED. Maybe i am asking for too much? Of course in the end it is the sound that matters. So what do you get when you go from the DI/O's $179 or so average street price to Audio Note's DAC Kit 1.2 $1,100 in kit form (not even built mind you)? Well, there are advantages... and some disadvantages too.

Dynamically, it seems to be about equal to the D/IO with upgraded power supply. While quite good, it simply did not have that 0 to 100 mph Ferrari speed. More like the DI/O's BMW 5-series. While quite good, it seemed as though there was shades of holding back. While not overly disconcerting, i also do not expect the dynamics of Audio Note's DAC 5 Special previously reviews here (at approximately $33,000!). The real advantage the 1.2 has is in what happen in-between the quietest quiet and the loudest loud within a piece of music, or instrument's reproduction.

The 1.2 is superlative in the ability to deliver microdynamics and subtle shading. Harmonic shadings are well rendered while there is more inner resolution. Is it the tube output stage? Is it the zero times oversampling? Beats me! Maybe it is all the aformentioned and how they interact. After all, a system is just that; a system where each part becomes the whole. While the DI/O has better pinpoint imaging between the loudspeakers, the 1.2 expands the soundscape in front of, beside, and around you. It reaches into the room and fills it completely. Some say this is where tubes are King over solid-state semi-conductor devices. Generalizations like "tubes image better than solid-state semi-conductor devices" can be dangerous so i will avoid saying it as some form of "proof" either way when it comes to imaging. i just hear what is happening in my dedicated music reproduction room and report on it accordingly.

Chesky's smooth and silky new release of Ana Caram Blue Bossa [JD219] has a more sensual rendering with the 1.2 than with the DI/O. It simply allowed the music to feel more seductive and tender. Teldec's Tchaikovsky 1812/Capriccio Italian/Swan Lake/Marche Slave [4509-90201-2] was a revelation! This recording has so much going for it that it allows dissection of a system in many different parameters. From massed horns to flute and, of course, big loud bangs as the orchestra plays full tilt. The 1.2 was a bit lacking in full tilt sorting of individual instruments, the DI/O suffers the same fate. On music that is more "progressive" such as hard core rock and true alternative, the 1.2 seems to have more feel to the beat over the DI/O's straight away beat. As a classically trained drummer for over 1/4 of a century, there is a difference between that of, say, a drum machine and a jazz drummer playing "in the pocket". There are subtle cues and timing that truly talented drummer allow to flow while a drum machine's cold-hearted chip-based beat tends to be flawlessly on time, yet flawed with less humanity. Mobile Fidelity's incredible remaster of Pink Floyd The Wall [UDCD 2-537] was proof enough that the Audio Note DAC Kit 1.2 was an emotionally more satisfying experience over the DI/O. From the small studio phasing tricks to gentle psychedelic flow.

Summit(ing) All Up

Many music lovers have been watching on the sidelines as DVD-Audio and SACD battle it out. Some have also found that the DAC within these new units do not offer top-end performance when playing their favorite music CDs. There may also be hundreds of thousands of people with older DACs hoping for some improvements within their current system. For only $179 street price the ART DI/O is a no brainer. Well worth auditioning as at this low a price it is hard not to give in to your desires and give it a go. The Audio Note DAC Kit 1.2 is not a quick fix, per se, as the DI/O. At $1,099 in kit form (plus an additional $200 for a completely assembled unit if you desire), this is more in the investment price range than a brief stop gap. Does the 1.2 provide the added performance for such long term musical enjoyment? In a word, yes. Accompanying a single word answer, i will add that the 1.2's better inner resolution, harmonics, and sense of rhythm (PRAT) should yield more long-term satisfaction. Both units are real world bargains. There is no doubt about it.  Still, the 1.2 offers more internal space for tweaking/upgrading plus provides a tube stage in the analog output section for those who love the glow. After all, in the end what really matters is that you... Enjoy the Music.

Below rating are for the Audio Note DAC Kit 1.2

Below rating are for the ART DI/O

Specifications

Art DI/O

Sample Rate: Switchable 44.1/48/88.2/96kHz - 128x oversampling 
Inputs and Outputs: S/PDIF and 1/4 stereo analog 
Tube Designation: Dual triode 12AX7 tube 
Channels: Two A/D and D/A Conversion 
External Sync Range: 22kHz to 100 kHz 
Digital Interface: S/PDIF coaxial input/output via RCA jacks 
Frequency Response: 10Hz to 30 kHz (+/- 0.5 dB) 
Dynamic Range: 100dB typical
Input Gain: +20dB
Input Level: +20 dB
Output Level: +20 dB (7 volts)
Input Impedance: 100K Ohms 
Output Impedance: 220 Ohms 
Power Requirements: 9vac at 0.8A
Price: $249 (street price $159-$189)

Audio Note DAC Kit 1.2

Input Receiver: Crystal CS8412CP
DAC Chip: Analog Devices 18-bit AD1865N
DAC Type: Zero times "oversampling"
Tubes: 6DJ8/6922 dual triodes
Output Impedance: 900 Ohms (+/- 5%)
Output Voltage: 3 Volts
Output Noise: <200uV unweighted, input terminated
Inputs: S/PDIF 75 Ohm (silver RCA) and AES/EBU 110 Ohm (XLR)
Analog Output: silver RCA jacks
Dimensions: 16.25 x 12" x 5.5" (DxWxH)
Weight: 23 lbs.
Price: $1,099 in kit form
Assembly Charge: $200

Company Information

Applied Research and Technology
215 Tremont Street
Rochester, NY 14608

Voice: (716) 436-2720
Fax: (716) 436-3942
Website: www.artproaudio.com 

Audio Note UK
25 - 127 Davigdor Road
Hove
East Sussex
BN3 1SG
England

Voice: +44 (0)1273 770 778
Fax: +44 (0)1273 773 476
Website: www.audionote.co.uk

USA Distributor 

Audio Note North America
2395 Cawthra Rd, Unit 15
Mississauga, Ontario, L5A 2W8

Voice: (905) 306-1677
Fax: (905) 306-9689
E-mail: audionote@idirect.com
Website: www.audionote.on.ca