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Camp Two - Empirical Rig vs. my Vecteur D-2 transport/tweaked out Audio Note DAC Kit 1.2
There are certainly those who are attracted to computer audio for its strong convenience factors: 1) being able to get rid of your CD collection, thus freeing up storage space, 2) playback of music at the click of a keypad/mouse, rather than getting up to load a CD, and 3) organizing your music in playlists, from which you can playback tracks in any order and continuously for long periods.

Then there are those like me who will not make this transition to greater convenience unless there is also a sonic benefit. Therefore, it is central to this review to elucidate whether computer audio, as supplied to me by Empirical Audio, outperforms my own Vecteur D-2 transport connected via S/PDIF to my tweaked-out Audio Note DAC Kit 1.2.

For this comparison, I uploaded as wav files using Exact Audio Copy two CDs that I used in my last review: Roseanne Cash's The Wheel [Columbia CK 52729], and Boz Scags' Some Change [Virgin 7243 8 39489 2 5]. With all of the complexity that I had to deal with for this review, I was in no mood to introduce a lot of new and unfamiliar music into the equation.

Overall, I would have to say the comparison was not a slam dunk for either rig. The Empirical setup had the strengths of cleaner, lower distortion sound with greater detail and macro dynamics. Vocals and instruments in the front stage were very slightly clearer, too. However, Roseanne's and Boz's voice were richer sounding (tubes?) with the Vecteur plus Audio Note combination. In fact, the entire sonic presentation was harmonically richer with the Audio Note. The Audio Note also had greater midbass weight and the upper mids and highs were smoother.

Before you conclude that computer audio is not worth it sonically, please wait for my discoveries and thoughts later in this review.

Camp Three - Empirical Rig in another system using Northstar 192 transport/DAC
My friend, Dan, recently bought the Northstar 192 transport/DAC which had some extensive mods done by Empirical Audio:
  • installed Hexfreds rectifiers
  • improved regulators
  • improved power filtering caps
  • improved power delivery - decoupling for the D/A chip, buffer chips, receiver chip, analog output circuits, including Black Gates and lot of other caps in various sizes and located in strategic places
  • reworked the termination of the I²S interface
  • did various board improvements to traces and ground planes for better signal integrity
  • improved post-DAC filter caps
  • improved D/A chip PLL filter caps
  • replaced several buffer chips with faster onesinstalled Superclock 3
  • further changes

The rest of Dan's system includes DIY Hifi Supply's Django TVC, Lady Day Cherry Special 300B amps, Bastanis Apollo speakers and Bastanis cabling. It seemed like a natural setting to insert the Empirical Audio Off-Ramp I²S since the Northstar DAC has the I²S input optimized by Steve Nugent. However, Steve Nugent informed me that I would need a different (inverse) I²S cable to interface between the Off-Ramp and the Northstar DAC. He sent one out quickly, but warned the Northstar ideally needs a special 5-volt Off-Ramp, but that I should get a good idea with the 3-volt Off-Ramp made for the Benchmark.

We started out listening to Norah Jones' "Painter Song" from Come Away With Me [Blue Note 32088] with the Northstar transport and DAC. This was one of the files also preloaded on the Toshiba's 16/44.1 playlist so it was a perfect track for comparison between the Northstar transport/DAC and the Toshiba/Off-Ramp I²S/Benchmark DAC-1. Both would be played back upsampled, 24/192kHz from the transport and 24/96kHz from the computer.

The Northstar combination acquitted itself well and was fuller on Norah's voice than the Empirical rig. It was also smoother, particularly in the treble where my one reservation about the Benchmark lies. In the Empirical rig's favor, it was a touch clearer on Norah's voice, with the whole presentation being cleaner as well as more detailed.

When discussing this comparison with Steve Nugent, he pointed out one caveat. Since he changes the output impedance of the Benchmark DAC-1 in his mods, he felt it might not be an ideal match with the Django TVC. We tried the TVC in both zero gain and 6dB gain mode. In speaking with Brian Cherry from DIY HiFi Supply about this match up, he advised using the zero gain setting. In practice, both Dan and I felt it sounded best in the 6dB gain position. We heard no typical impedance mismatch problems such as rolled-off highs.

Next, we kept the computer and Off-Ramp in the system but switched from the Benchmark to the Northstar DAC, being careful to note that the DAC was sensing a 96kHz input signal from the upsampling of the computer. If I had to choose one combination, this would be it. Now, we got the best of the computer/Off-Ramp sonics along with the smoothness of the Northstar DAC.

Steve Nugent claims that the computer/Off-Ramp I²S does a better job of playback than any optical transport. Based on this comparison with a very high quality, Empirical Audio-modified Northstar transport, I would be loath to bet against him. Steve Nugent also has a Superclock 4 mod for the Northstar transport which he feels could greatly narrow the gap. .

Continuing down the playlist with the computer and Northstar DAC, the hallmark sound of the Off-Ramp I²S became increasingly apparent. From Mussorgsky's Night on Bald Mountain, St. Louis Symphony under Leonard Slatkin [Mobile Fidelity SACD UDSACD 4004]), through Massenet's Le Cid [Klavier KCD-11007], clarity, detail, bass authority and a low distortion presentation overall was evident. This was the best that Dan's system had ever sounded.

Replacing the Northstar DAC with the Benchmark one more time was a mixed bag. When the percussion comes in on the title track of Roseanne Cash's The Wheel, the Benchmark had more crunch power but it was running at the proper voltage and that might have been a factor in its favor. With playback of the Led Zeppelin tracks, the slight treble edginess of the Benchmark came through again.

While I preferred the tonal balance of the Northstar DAC, the greater clarity and better dynamics of the Benchmark were very appealing. It's all a matter of how the Benchmark's treble integrates in your system as well as your perspective on the accuracy/musicality debate.

After discussing my findings with Steve Nugent, he felt that the highs might be smoother in the Northstar because it has a discrete output stage versus the op amp output stage of the Benchmark. The greater clarity of the Benchmark is likely due to the newer generation, better spec, AD1853 DAC chip. The Northstar uses the older CS4396/7 D/A chip, which is the same as used in the Perpetual Technologies P-3A DAC that Steve used to modify. Perhaps a DAC with the AD1853 DAC chip and a discrete output stage (along with Steve's other goodies) would be the best of both worlds.

Or, better yet, I would like to hear the Empirical Off-Ramp I²S into an I²S-input modified Audio Note DAC. [Below, Steve Nugent's brand-new Spoiler DAC.]

The summit - Empirical rig with native 24/96 files
I'd been playing selections from the supplied 24/96 playlist all along but it was now time to focus on this aspect of the Empirical for the review. At first, I was playing these files and wondering about where Steve Nugent got this music. I asked him about one in particular and he said it came from High Definition Tape Transfers. All of the 84 selections were transferred at 24/96 onto DVD discs and then uploaded onto the Toshiba hard drive.

There were a few just okay tracks in this playlist, but oh my, a few of them stood out as some of the best recordings I've heard in my life. One that really did it for me was "What's New" from Frank Sinatra's Only the Lonely [24/96 transfer from 2-track tape, Capitol, 1958]. A woman friend of mine who appreciates music from that era was visiting me one evening. I sat her down in the sweet spot and played this cut for her. I thought she was going to melt right into my sofa. If you don't swoon when hearing this track, you are made of stone! Frank's voice was just sublime and the Nelson Riddle orchestration perfect as usual. No problems with treble on the Benchmark when playing back this caliber of recording.

The point to be made here is that the computer allows you to upload and playback, without the need for upsampling, this high definition source material. It is the path to the ultimate sound quality, as far as I know. That is, unless you are playing back the original tape masters! Even then, you better have a darned good tape deck.

A careful descent - PC computer playback with and without upsampling
In the last day I had this rig, I realized that I had neglected to investigate one of the major features available to PC users of computer audio - the SRC Resampler upsampling software. In the past, I have not been overly impressed with the benefits of upsampling and have been sympathetic to the camp that eschewed it.

To disengage the upsampling, the user needs to change settings in M-Audio Transit panel as well as in Foobar Preferences Playback and Foobar Preferences DSP Manager. These changes are outlined in the setup instructions from Empirical Audio.

Toggling back and forth between upsampling and no upsampling, I was able to discern a number of clear benefits to the upsampling. I decided to upload the CD Art Farmer Ph.D. [Contemporary CCD-14055-2] to the playlist and played the first three tracks over and over, upsampled and not. The track "Affaire d'Amour" illustrated the differences well. With upsampling, the trumpet bloomed more into the room and the tone was harmonically richer. The upsampling also provided more detail, greater nuance and better soundstage dimensionality. There was just a greater sense of verve, with the tension behind each note of Art Farmer's playing more palpable.

One observation I made that struck me as odd was that the cymbals and other high frequency content were more prominent with upsampling engaged. On this same Art Farmer track, the cymbals were almost a bit distracting to the overall balance. This may be less noticeable on a DAC other than the Benchmark. In this one aspect, I preferred the playback without upsampling. I cannot propose any logical explanation for this observation but I am quite sure that I heard it.

The other issue with SRC Resampler is that you will hear more ticks and pops than without upsampling. Again, according to Steve Nugent and many others on Audio Asylum, with persistence, these can be eliminated. Overall, the improvements I heard from the SRC Resampler were better than I had experienced in upsampling CD players. I decided to research this a bit more and did some reading on the Audio Asylum PC-Audio discussion. Coincidentally, I found a post by Steve Nugent that directly addressed and explained my observation: "The bad rap the upsampler have (sic) gotten is due to the implementation in the hardware upsamplers. Using Foobar, you can choose the best algorithms and the result is quite spectacular compared to 44.1."

I must admit that SRC Resampler, interfacing it with the Benchmark DAC-1 with its upsampling circuitry removed, has turned my head around about upsampling.

Return to base camp - Toshiba versus Apple MacBook with 16/44.1 files
Having recently purchased a new Apple MacBook, I decided to see if there were any discernible differences between playback of 16/44.1 wav files without upsampling, using iTunes with the MacBook and Foobar with the Toshiba. The Empirical Audio web site ranks the Apple ahead of PC in playback of 16/44.1 wav files. I was short on time as this point, being under the gun to wrap up the listening and get the gear back to Steve Nugent in time for the looming Consumer Electronics Show. Given this time limitation, I cannot state that I could hear any significant differences between the two. From a non-sonic point, however, the MacBook ran quieter. The Toshiba's cooling fan, which cycles on and off, could intrude on the music in quieter passages. Fan noise is a consideration if you plan on using a computer near your stereo, which is necessary with USB playback. Steve warns that the USB cable should not be longer than five meters since that's the limit for USB protocol. Active hubs or power injectors can of course extend that.

Head count
On the night before I had to return the Empirical Audio rig, I went back and played the Led Zeppelin tracks (e.g. "Bring It On Home"). It is amazing to hear these Hard Rock masterpieces in the light of such high quality playback. While there is a rawness to them that can't be denied, it is surprising to hear the wealth of information that is on these recordings. The Empirical Audio computer playback system unraveled what was really a very sophisticated interplay between the musicians that I had never been able to fully appreciate before.

Based on the fact that the computer/Off-Ramp I²S/Benchmark bettered the Vecteur/Benchmark when playing via S/PDIF, and that it outperformed the Empirical Audio modified Northstar transport in my friend's system, I would strongly recommend the Empirical Audio Off-Ramp I²S solution to computer audio. Buyers should be just as careful in selecting the DAC they pair with the Off-Ramp I²S as they normally would in buying any DAC. No surprise here but sorting out the relative sonic contributions of each of the components in this playback chain took some work.

I would proffer that Steve Nugent is indeed on the cutting edge of computer audio playback and at the cusp of a true breakthrough in computer audio playback. If his new Spoiler DAC (not a mod) has the clarity, dynamics and transparency of the Benchmark and the smoothness and richness of the Northstar, then he will have truly reached a new pinnacle of sound, computer-based or otherwise. As it is now, the combination with the Benchmark DAC-1 will be stunning to many if matched in the right systems.

Of course, before plunging into computer audio and/or the Empirical Audio Off-Ramp I²S/Benchmark DAC-1 package, make sure you are willing to:
1. Take the time to upload your compact discs to your computer, or as a friend of mine says, hire a personal assistant to do it for you.
2. Fiddle with settings to eliminate ticks and pops.
3. Dedicate the computer (laptop) solely to music playback. Tying up the I/O port with other programs is inadvisable.
4. Spend a not inconsiderable sum on a rapidly changing technology.

Regarding the final caveat, computer audio has a distinct advantage. Some of the upgrades will turn out to be software-based, saving you the usual hassle of selling off old hardware and buying new. In fact, the most significant software upgrade to benefit computer audio is promised by Steve Nugent's recent post on Audio Circle: "I have another project in the works for next year that will use my own Empirical Audio driver and the TUSB3200 from TI. It will run Asynchronous protocol on the USB cable." This could eliminate the need to fiddle with settings to eliminate the pops and ticks.

Speaking of rapidly changing technology, Steve is demonstrating his very latest product, the Pace-Car, at CES 2007. To quote his website: "This is a reclocker that inserts between the Off-Ramp I²S and the I²S input DAC. Early prototype demonstrations with P-3A DAC resulted in the best detail rendering I have heard. The jitter at the D/A chip is simply that of the modded Superclock4. Quite remarkable sound. This device should be usable with any I²S DAC and the modified Off-Ramp I²S. It also galvanically isolates the computer from the audio system. No pricing generated yet, but I plan to make it available Q1 2007... I will demonstrate it at Las Vegas in January."

Feeling dizzy yet?
Publisher's comment:
In December 2007, we received the following note from Steve Nugent, designer at Empirial Audio: "During the review, Stephen noted that the pops and ticks with the USB computer playback were not entirely eliminated by his efforts. In response, Empirical Audio has licensed a new USB firmware at considerable expense. This replaces the M-Audio USB drivers and firmware that we were using previously. The new firmware dubbed "driverless" uses the lowest levels of the Windows driver infrastructure so that a custom driver is not necessary. It is also compatible with Vista. The sound improvement with the new USB firmware is significant - and no pops and ticks now."
Manufacturer's website