Friday 19 April 2013

GUEST REVIEW & MEASUREMENTS: The Dr. Frank's "Best-Coaxial-Digital"™ SPDIF Cable.

By Keaton I. Goulden-Eyre III, Esq.

Two months ago, I had the good fortune to meet my independently wealthy friend Stephen at the local smoking lounge where 'the men' gathered to speak of recent developments in politics, finances, and what ails the common man. He mentioned that on a business trip to Yangon last year, he took a day off and was warmly received by representatives of Dr. Frankenstein's Audio Immersion Labs (FAIL) for a tour of a new manufacturing facility where only the best audio cables were to be produced by specially trained artisans by hand for export to rich Western nations where citizens truly appreciate the finer things in life. Within months, they were to start production of what was no doubt the best digital coaxial audio cable money can buy, to be followed by a full line of power cords, USB cables, and mineral-based sonic enhancers.

I was immediately intrigued! Post-haste, I contacted the legendary audiophile hardware importer Mr. Suet Shappeé in Luxembourg, the closest FAIL distributor to inquire about the state of the manufacturing facility and whether samples of their digital cable (code named "Siren") was available to audition.

"It's taking much longer than anticipated!" was his frank response. Apparently, the exact specifications for this product had just been cleared by the R&D-heavy company, run by the famous Japanese audio designer Dr. Seiji Minoeall working from his secret laboratory near Akihabara in Tokyo. Rumors are that the complexity of the computer simulations required to achieve the optimal design had to be debugged by the top 3 quantum mechanics physicists in the world working straight for 9 months!

"However, I am pleased to tell you the 3rd cable just came off the assembly line yesterday!" was finally Mr. Shappeé's response with much prodding on my part. Finally, after two hours of heavy negotiations, he agreed to send me a sample for review. Word on the street is that these cables are in so much demand that at the introductory price of $4999.99, it might take 1 year to satisfy the pre-orders! I felt honoured to be selected by FAIL as the first reviewer in the audiophile press to have access to this most rare and remarkable high-end cable.

Under strictest secrecy, I was directed to contact Minoeall-san for some further information about the product as well as design philosophy. "You know Keaton, audio is life. And like life, only the most complex can integrate the self-evident." I knew immediately I was speaking with one of the most learned designers I have ever conversed with. When he was young, Minoeall-san was raised by the monks of Mount Fuji where the simplicity of life taught him that the world around him was much more complex. On his frequent visits to the Kabukicho district of Shinjuku, Tokyo, he learned that in order to find truth and reality, one had to embrace the complex. It is with this wisdom that his creation was inspired. As fortune would have it, in 2001 Minoeall-san was visiting a high-end audio show when he met with representatives of Dr. Frankenstein Audio Immersion Labs and a joyous union was formed! "I have poured my life into the perfect design of this cable"; Minoeall-san confided in me during that intimate conversation.

Within 2 weeks of our discussion, an insured 50.8 pound Myanmar oak chest arrived at my chateau. The courier postman asked me - "what the **** is this? Gold?" Indeed, sir, pure audio gold!

I opened up the immaculately silk wrapped package to reveal the amazing new "Best-Coaxial-Digital" (aka Siren) cable - feast your eyes on the ultimate workmanship:

I will let Minoeall-san describe the exclusively patented 3-segment construction:
"Keaton, remember that in digital audio bits are NOT bits. There's just so much more that we've discovered in the last 20 years! Through deep metacognitive-quantum-mathematical research contracted with Top universities and the aerospace-defense sectors, we have determined that 3 is the ideal number - it is God's number - like the Holy Trinity.

"As more heads than one improves intellect, so too do extra connectors add to the coherence of the sound. This is why we used a triple-headed length on one end - this baby is totally overbuilt and even has the capability to conduct composite video if necessarily (note that the red connectors were used because red connectors were best to convey passion). We determined 10' as the optimal length for the first segment because it is. We then channeled the sound into a second triple headed 6' length where the audio is further refined and the well-recognized jitter is attenuated. We do this by making sure there is no gold plating since the gold-aluminum interface slows down the electron transition and induces timing artifacts. The final segment is a double-headed slim-line linear core design. It's only 3 feet long to speed up the final stretch for the electrons. The electrons will arrive at the DAC faster and this improves timing and coherence of the hi-fi signal, thus absolutely removing the jitter. With this new design, archaic concepts like impedance matching has become irrelevant.

"Some audiophiles may be surprised by the 19' length of this most wonderful of cables. As we all know, a short digital cable is bad. Too many electrical reflections distorting the leading edges of data transitions, confusing the DAC and creating digital errors. That is why the 'Super Connector' between each segment consists only of the best high-tech pliable organic polymer and aluminum. Any reflection will be subdued going across the connectors and rendered impotent.

"One more thing - gold is over-rated. It sounds bad because it's too shiny. It sounds digital - metallic and shiny like the CD. This is also why we do not believe in excessive shielding...  Remember, only complexity can convey the simplicity of truth - electromagnetic fields around us are complex, let us embrace this to finally create a cable worthy of the Best Music!"

Clearly, I realized this man spoke truth - finally, a sane voice in a cacophony of technobabble!

Subjective Analysis:

After taking that picture above and the unboxing video, it was time to plug the cable in. I connected it to my heavily modified Playstation 1 with digital output to another heavily modded tubed-NOS-DAC custom made for me by a local artisan-engineer consisting of specially selected chips, capacitors, and resistors based on auditory properties most engineers cannot comprehend. Likewise, my horn speakers and tube SET amplifier were custom made 'en bloc' by a one-armed carpenter in the city of Kuala Lumpur who specializes in the lost art of "tuning by ear". All analogue cables were of the rare cryogenically treated ninety-nine nines copper insulated by "active shielded" Super-Kapton connected as bare wires to the equipment with lengths conforming to strict golden mean ratios. Cable risers are of course essential. Obviously, only custom matching can achieve the synergy required for the finest audio reproduction.

I made sure to run the gear with the cable attached continuously for 2.5 weeks, getting my daughters to change CD's every couple of hours. This was only 420 hours and I am sure the "Best-Coaxial-Digital" Cable would continue to improve into the manufacturer suggested prerequisite 500 hour burn-in period.

To start, I put in the fantastic blues sound of Muddy Waters' "My Home Is In The Delta" (Folk Singer, Classic Records). In a word: stunning! My jaw and dentures almost dislocated. I have never heard so much air around the guitar in this 1964 recording. It was like being there marveling at the artistry of Mr. Waters. The resolution was so clear that I could envision the finger movements over each guitar string and the beads of sweat running down his cheek as he pined for that most beautiful of abodes - his home.

Next, I sampled the lovely rendition of "Love Of My Life" (A Night At The Opera, 1975, DCC) by Queen. By far, the 70's were the best! I met my 3rd wife when this song was released - great memories! Again, this cable did not let me down. Freddie Mercury has never been so romantic. Forget veils, my friends; never has an obstruction been parted like this since Moses parted the Red Sea. The liberation was epic. For a few minutes, I was 35 again with my girlfriend in my fifth generation turbocharged Chevy Impala.

For a taste of live music, I turned to Eric Clapton's "San Francisco Bay Blues" off his Unplugged (1992) album. What organicity! Not only could I hear every toe tap, wrong note, timing error, but I could literally smell the hint of cannabis wafting from the hooligans sitting 4 rows back from the stage. The soundstage enveloped my cubical listening room! I was astounded that so much detail could be preserved, retrievable only thanks to these digital cables.

Finally, I just want to speak of my favorite genre - classical music - the most highly refined of all genres. Obviously, classical music can only be appreciated with the best digital gear (but any analogue gear will do) due to the supreme intricacy and intimacy only this form of music can convey to the soul. Consider for example how totally inadequate any MP3 version of classical music becomes. I digress. I put on my favorite Mahler symphony - Symphony No. 9 conducted by Rafael Kubelik & The Bavarian Radio Symphony Orchestra (recorded live in Tokyo, 1975, re-released in 2000). The fine rendition of strings in the final movement contrasted lovingly with the percussion in the Rondo-Burleske so perfectly that my eyes welled up in tears, gave me palpitations, and triggered my pacemaker. How sad that Mahler himself never lived to hear his final angelic masterpiece. At one point, my luscious young wife Candy poked her head out of the drawing room and commented "that's a fantastic vinyl!" - I grinned like the Cheshire Cat.

To confirm these findings, I invited my best friend, the musician Jonathan C. Wiltkinshireshire II to hear these cables. As we listened over a glass of fine single-malt scotch whisky and puffs of freshly imported Cohibas, he commented on the "resolute ease" of presentation and "perfect liquid presence" of these cables. I could not agree more.

Of course for the remaining precious moments with the "Best-Coaxial-Digital" SPDIF Cable, I auditioned numerous landmark recordings from Chesky, Blue Coast (my only regret was that I could not audition in pure DSD), MoFi, Audio Fidelity, Classic Records, Reference Recordings, AIX, 2L, B&W, Linn, etc. My cup overfloweth with audiophile delight thanks to this cable. One parting observation as I begrudgingly conclude these "subjective" comments - I have never heard Rebecca Pidgeon's shakers ever go that "deep" into the soundstage on "Spanish Harlem"!

Objective Analysis:

First, let me make it clear that this section is utterly unnecessary. Everyone knows that my ears are superior to all other imperfect measurement devices (after 73 years of life experience, I have heard every relevant song ever produced by any audiophile label and am certain that my auditory acuity and frequency response have never been better). It is because my Commoner-associate Archimago demands that this section be included that I am even wasting my time documenting this. It's insane that anyone can come to any conclusions using free software and decidedly "pro" audio hardware! Nonetheless, let us obtain some numbers...

Firstly, let me introduce you to the inferior comparison "digital" cables:

Cable A is a feeble short 3' length of shielded coaxial from Radio Shack Canada before they went defunct a number of years ago. Cable B is a mass market 6' "digital audio" cable from Acoustic Research produced in China. I bought this one 13 years ago so I am confident it's worthless since the science of digital audio has moved ahead multiple generations. Decidedly pedestrian.

Cable C is insanely long at 25' marketed by Acoustic Research as a shielded "subwoofer cable". Obviously this is an analogue cable and I would dissuade anyone from considering this in the digital domain. I noted that there is "directionality" with some arrows pointing the flow of electrons. Despite my protestations, Archimago insisted I hook the cable up backwards (the man is truly an anarchist).

So, using his audiophile unapproved "usual" testing hardware:

Win8 laptop --> 6' shielded USB cable --> CM6631A asynchronous USB-to-SPDIF --> *test digital cable* --> AUNE X1 DAC coaxial input --> silver braided RCA --> E-MU 0404USB --> Win8 laptop

RightMark Audio Analyzer 6.2.5 Summary (24/96):

Preposterous that the beauty of musical hardware can be reduced to "bels". Seriously, bells are so passé (especially the tubular variant), they barely play a significant part in any respectable percussion section.

Frequency Response:

Noise Level:


Stereo Crosstalk:

That purplish color for the "Best-Coaxial-Digital"™ is clearly regal and hence the best. Cable A was too short, Cable B was too cheap, and how dare anyone hook Cable C up against the clearly marked electron directional flow and expect good results?!

Jitter analysis (16-bit and 24-bit):

Cable A:

Cable B:

Cable C:

"Best-Coaxial-Digital"™ SPDIF Cable:

Squiggles, squiggles everywhere. Who know what this means, but I am sure the "Best-Coaxial-Digital"™ performed superbly compared to the other questionably designed plebian pocket-change cables in the jitter.


As you can see, the objective results were utterly pointless and do not explain the sunny vs. total eclipse audible difference whatsoever. Anyone who listens without noticing a difference must have sensorineural hearing loss. As I told Archimago, the complexities and incalculable dimensions of music are so expansive, one cannot possibly expect a few simple measurements, ABX, DBT, ABC, NBC, CBS or CNN efforts to have any correlation with hardware quality. I echo those wise words of Minoeall-san: "only complexity can convey the simplicity of truth". My wife knows this, my audiophile friends know this, the righteous gentlemen of the audiophile press are well aware of this truth and have done their utmost to educate the unsophisticated masses. Even my 4 year old grandson told me the other day "hearing is believing, grandpa." Yet I digress again...

This fantastic coaxial SPDIF cable has earned the KASH (Keaton's Audiophile Superior Hardware) Jadeite Studded Platinum Award and rightly deserves to be included in any A++++ list of digital gear. In fact, it's so good, I wish I could create a category called "semi-analogue"! It was with great regret that I had to pack up these cables after this review to return to the manufacturer. Due to élite availability, this set I borrowed had to be sent off immediately to a billionaire buyer in Beijing who was glad to know that I had almost completely burned-in these amazing cables. Very soon, Mr. Suet Shappeé in Luxembourg will be opening a showroom (Delüsion Audio Arts GmbH) to highlight the full line of Dr. Frankenstein's Audio Immersion Labs gear and any serious audiophile would be well advised to experience this cable for themselves. You will be utterly enraptured!

One last detail, the introductory price of $4999.99 will only be available until December 31, 2013 (increasing to $5888.96 in 2014). For the level of performance, this is a fantastic deal. Minoeall-san was firm regarding the pricing when he told me "I cannot sell this for a dollar less if I want to recoup my R&D costs!" I am astounded by the honesty and philanthropy demonstrated by this company.

Ed: Enjoy the music.

Monday 15 April 2013

MEASUREMENTS: USB Cables for Audio DACs. [2013-06-18 UPDATE]

Up to this point, as you've seen in my measurements, I have been using standard generic shielded cables for analogue and digital. As you likely also know - if you've been involved in "high end" audio for awhile - there are few issues as contentious as whether expensive cables are necessary or if they even make a difference!

I've generally steered clear of this "debate" over the years because inevitably, these discussions with friends or forum threads on-line almost never really "go" anywhere...  Nobody leaves the discussion having really learned anything, and ultimately if the discussion turns into an argument, everyone just ends up feeling "pissed off".

The conclusion one usually can get agreement on is that the best cable is no cable. Cables are passive "components", and ideally should transmit signal without loss, and does not impart any kind of signature on the quality of the signal. This certainly makes sense especially in the analogue domain where noise can easily creep in, causing various distortions or raising the noise floor. But what of digital cables? When something as ubiquitous as a generic USB cable can easily transmit >20MB/sec data to a USB hard drive, how problematic can it be to get 150KB/sec across for 16/44, ~500KB/sec for 24/96 audio, or 'just' ~1.12MB/sec for 24/192 high-resolution audio!?

After all these months of testing and posting on various topics, I figure it's at least reasonable to explore the cable issue as best I can with (admittedly) the limited selection of choices I have available around here.

For the record, up to this point in time, the most expensive USB cable I have tried has been the AudioQuest Carbon (~$160 for 5') more than a year ago connected between the PC and a Benchmark DAC1 USB. I have since sold off both items. I could not clearly hear a difference with the AQ Carbon, but then again since the DAC1 uses ASRC, I really wasn't expecting much either. Since then, I've been satisfied with the selection of generic cables I've collected over the years as computer parts or 'freebies'. It is in this light that I selected among my assortment, 3 A/B USB 2.0 cables to test out:

USB Cable A:
- 3 feet long
- not gold plated
- ferrite core on the B end

USB Cable B:
- 5 feet long
- gold plated A & B ends
- no ferrite core

USB Cable C:
- 17-feet long! (6 feet Logitech extender, 5 feet Linksys extender, 6 feet generic cable)
- not gold plated
- possible ferrite core on the extender connections?

As you can see, Cable C was made by Dr. Frankenstein. It's unreasonably long (USB specs indicate a reasonable limit at ~16'), has 2 detachable connections in between, is not even gold plated, and who knows what kind of shielding is in that thing. Furthermore, the Logitech extender portion has the thinnest wire of all the cables. Any card-carrying "audiophile" would be laughed out of town for even suggesting they use something like this!

I. Cables tested with Asynchronous USB 2.0 CM6631A interface:

Aspire Win8 laptop --> *test USB cable* --> CM6631A USB to SPDIF --> Generic TosLink --> AUNE X1 DAC --> silver braided RCA --> E-MU 0404USB --> Aspire Win8 laptop

Let us start with what has been previously demonstrated to be a very robust asynchronous USB interface; the CM6631A. Remember that the previous tests showed that despite different laptops used, the analogue and jitter spectra were almost identical.

With the different USB cables, RightMark DAC analogue analysis (24/96 used):

Frequency Response:


Stereo Crosstalk:

No difference.

Dunn Jitter Tests (16-bit & 24-bit tests):

Cable A:

Cable B:

Cable C:

No difference.

II. Cables tested with Adaptive Isochronous USB 1 AUNE X1 interface:

As shown previously, this interface can get noisy if I play and record with the Aspire laptop (see the laptop post). Therefore I'm going to use my ASUS Taichi to play the test audio while measuring with the Aspire as usual.

ASUS Taichi --> *test USB cable* --> AUNE X1 USB1 --> silver braided RCA --> E-MU 0404USB --> Aspire Win8 laptop

RightMark DAC analogue analysis (16/44 only):

Frequency response:


No difference.

Dunn Jitter test (16-bit only):

Cable A:

Cable B:

Cable C:

Well, the adaptive USB interface is noisier and more jittery than the asynchronous setup as we have seen before in previous posts. Depending on which cable, we can see noise showing up at certain frequencies. For example, there's a -120dB 11.7kHz spike on Cable A, 11.3kHz for Cable B, 10kHz for Cable C. But these are not the symmetrical sidebands associated with data jitter. In fact, the low-frequency jitter associated with widening of the base around the 11kHz signal looks essentially identical and perhaps most importantly, there's really nothing unusual here to suggest that Cable C is of unusual length and construction!

III. Cables tested with TEAC UD-501 Asynchronous USB 2.0 DAC: (2013-06-18 Update)

For the sake of completeness, I decided to run these same "cables" through to the direct asynchronous USB 2.0 interface of the TEAC UD-501 DAC to see if we can see any differences. Some folks asked if I could try a "name brand" cable for point of reference...  Suggestions included the AudioQuest Diamond, maybe some Crystal Cables... Well, I search high and low... And here's the Belkin Gold 6-ft (1.8m) which I managed to get on sale for <$10 locally :-)

That red stuff is just some electrical tape I put on it for identification on another project.

Here's the RightMark data for 24/96:

Frequency Response:


Stereo Crosstalk:

No difference.

Dunn Jitter Tests (16-bit & 24-bit tests):

Belkin Gold (6'):

Cable A (3'):

Cable B (6'):

Cable C (17' monstrosity):

As you can see, the jitter plots for the TEAC are quite clean. On the whole, the 24-bit noise floor is measurably lower than the AUNE X1 but the jitter plot does show a few more noise spikes (made more obvious because of that low noise floor). This is really quite academic because we're talking about noise down near -140dB!

No evidence of significant jitter differences between the Belkin Gold or any of the other cables including that terrible looking Cable C (17-footer).


No evidence in these tests to suggest that the different USB cables used here with the asynchronous CM6631A USB-to-SPDIF converter, direct asynchronous TEAC UD-501 USB DAC, or adaptive isochronous USB setups should sound different (even though one would expect Cable C to be the worst). Subjectively, listening to music with Cable C through Sennheiser HD800's sounded fine. 

No evidence with the J-Test to suggest data-correlated jitter is significantly different between cables. By the way, for a good demonstration of how jitter improves with interface/cable change, look at my post on Transporter-to-Behringer connection with TosLink vs. AES/EBU. Also, remember that my Oppo BDP-105 tests were done with a single 15' USB cable - still better than Cable C in construction :-).

As usual, feel free to drop me a note if there's good data or controlled tests to suggest USB cables make a significant difference contrary to these findings.

Happy listening...

Saturday 13 April 2013

MEASUREMENTS: Laptop Audio Survey - Apple MacBook Pros, Acer Aspire, ASUS Taichi...

Now that the asynchronous CM6631A USB to SPDIF device works well on the Mac with full access to sample rates after removing that reset chip, let's have a look at a few of the laptops I have around here - how the internal DAC's measure and compare this to the effect of disparate hardware on adaptive USB and asynchronous USB DAC's. First up, let me introduce you to the laptops I'll be testing:

1. Early-2008 17" MacBook Pro (MBP):
     CPU:  2.6GHz Core 2 Duo
     Memory: 6GB 667MHz DDR2
     Graphics: nVidia GeForce 8600M GT 512MB
     OS: Mac OS X 10.8.2
     HD: Corsair GT 240GB SATA SSD
This has been my work laptop for a few years until a couple months back. Essentially top-of-the-line laptop back in 2008 when I bought it. Still looks good and works well! I updated the hard drive to an SSD and upped the 4GB to 6GB about a year back.

2. Mid-2009 15" MacBook Pro (MBP):

     CPU: 2.26GHz Core 2 Duo
     Memory: 8GB 1333MHz DDR3
     Graphics: nVidia GeForce 9400M 256MB
     OS: Mac OS X 10.8.3
     HD: WD 640GB SATA
My wife's work laptop. One of the Apple UniBody construction machines. The only laptop in this roundup with a hard drive rather than SSD.

3. Acer Aspire 5552-7858 (17"):

This is the least expensive of the laptops; priced at <$600 when I bought it new in 2011. This is also the machine I've been using over the last months for all my "mobile" data collection such as the Oppo tests at my friend's house. Mostly used by my kids and guests if they want to look something up. SSD upgrade about 6 months back.
     CPU: 2.2GHz AMD Phenom II X4 N970
     Memory: 6GB 1333MHz DDR3
     Graphics: ATI Mobility HD4250
     OS: Windows 8 x64
     HD: OCZ Vertex2 120GB SATA SSD

4. ASUS Taichi 21 DH51 (11.6" dual screen):

My newest "ultrabook" laptop (bought February 2013). I know the reviews are mixed but IMO, this is a fantastic mobile laptop / tablet with a high resolution 1080P matte screen in laptop mode and glossy touchscreen as a tablet! Everything in one light and mobile package; fantastic to use in the local coffee shop to update one's audio blog :-). Great for work and although the battery life is at best average in power saving mode, good enough for me with light Office duties.
     CPU: Intel Core i5-3317U (1.7GHz)
     Memory: 4GB 1333MHz DDR3
     Graphics: Intel HD 4000
     OS: Windows 8 x64
     HD: 128GB SSD mSATA
Note that this unit doesn't have USB2 - tested with USB3 ports.

I. NATIVE DAC (RightMark Analogue output analysis):

First, let us have a look at the internal DAC's in these laptops. Measurements were done as follows:
Laptop headphone out --> shielded phono-RCA cable --> E-MU 0404USB --> Aspire AMD laptop

In order to try to ensure "bit-perfect" output, I used Decibel 1.2 on the Macs (turned off all volume adjustment, allowed Decibel to have exclusive access, buffered audio files to memory). On the Windows 8 side, playback was with foobar2000 1.2.4 (latest stable version) playing back with either WASAPI with no dithering or ASIO if driver available.

As you can see, each laptop demonstrated significantly different measurement results. Every one is capable of handling 24/96. The frequency response graph for each machine looks different, especially between the MacBook's vs. Windows machines (perhaps the Acer and ASUS use similar OEM DAC hardware?).

Not surprisingly, the ASUS has the highest noise floor of the 4 machines. It is an "ultrabook" so there's a lot of electronics packed into that case plus the headphone out jack is right underneath the screen hinge (instead of closer up front by the keyboard like the other machines).

I'm impressed by the MacBooks though with >100dB dynamic range! That's fantastic for laptops and certainly as good as lesser "audiophile" DAC's out there.

 II. Adaptive Isochronous USB (RightMark Analogue output analysis):

Using the AUNE X1 (Mark I) as the DAC, let's look at the relative performance of each machine using the X1's USB interface - the old "adaptive isochronous" BB PCM2707 USB1 technology measured at the usual CD sample rate of 16/44.

Test laptop --> Shielded USB cable --> AUNE X1 --> Shielded RCA --> E-MU 0404USB --> Aspire laptop

Notice how close the results are except for the Aspire-X1 results. Obviously since we're now utilizing the same DAC for each machine, the sound output is dictated by the properties of the DAC. The difference with the Aspire-X1 setup is that the Aspire is both the test machine and the measurement device (loopback setup). This means the Aspire needed more CPU processing and had much higher USB traffic than the other machines (maybe the mixed USB1 & USB2 modes have something to do with this). What we're seeing is likely electrical noise generated by the busy machine, and as I'll show later, this is NOT likely due to significant timing jitter in the digital domain.

Otherwise, I see no significant difference in measured "sound" coming out of the DAC whether the machine is Mac or Windows despite the significantly different underlying hardware, OS, playback software, etc... 

 III. Asynchronous USB (RightMark Analogue output analysis):

Test laptop --> shielded USB2 --> CM6631A --> inexpensive decent 3' TosLink --> AUNE X1 --> E-MU 0404USB --> Aspire laptop

Look at what happened with the asynchronous and very inexpensive ($50) CM6631A performing USB to SPDIF duties! Audio output from the AUNE X1 DAC is now IDENTICAL from every laptop. This shows that compared to the USB1 input to the X1, the CM6631A converter, in using TosLink provides excellent electrical noise rejection from the USB port (note that I'm running the converter USB powered; NOT separate power supply even). I think this is a nice demonstration of how the TosLink interface has its place despite measurably worse jitter in some cases.

IV. Jitter - Native DAC:

The Dunn J-Test was created to look at jitter in SPDIF interfaces, therefore there really should not be any issue with built-in DAC's for each laptop. Reminder, "bit-perfect" settings for Decibel with the Mac's, foobar2000 WASAPI 16-bit undithered for the Windows machines used. Here's how the 16/44 J-Test result looks for each machine:

2008 17" MacBook Pro:

2009 15" MacBook Pro:

Acer Aspire:

ASUS Taichi:

Quite different spectra as you can see. What is learned from the graphs is NOT jitter but rather the loss of the jitter modulation pattern with the 2008 MacBook, Acer Aspire, and ASUS Taichi. This means that despite using bit-perfect settings with the players, these computer DAC's are incapable of "bit-perfection". Other than the 2009 MacBook Pro, all the other machines either truncate or perhaps have some kind of 'forced' dithering in place such that the LSB jitter modulation has been corrupted.

V. Jitter - Adaptive Isochronous USB AUNE X1:

Using the same method, lets look at the jitter pattern with the USB1 interface built into the AUNE X1 (Mark I). Again either using Decibel or foobar2000 with bit-perfect settings in place. USB cable is generic shielded good quality 6' cable:

2008 MacBook Pro to AUNE X1:

2009 MacBook Pro to AUNE X1:

Acer Aspire to AUNE X1:

ASUS Taichi to AUNE X1:

As you can see, the jitter modulation tone can be see in each situation. This confirms that indeed bit-perfect data is being sent to the DAC containing the LSB data. If anything, it looks like the Mac's may have a few more jitter sidebands than the Windows machines. If you recall from the RightMark results above, the Acer Aspire is performing both playback and recording duties in this situation so you can see that the noise floor is higher than for the others (noise increases significantly in the lower frequencies as shown in the RightMark graphs) likely due to the increased CPU and USB activity causing noise to spill over into the X1 DAC through the USB electrical interface.

VI. Jitter - Asynchronous CM6631A USB to TosLink to AUNE X1:

What about when the CM6631A is used? Two things are happening here - USB communication is now asynchronous allowing better clocking (ie. lower jitter), and galvanic isolation is also happening by way of the TosLink SPDIF intermediary. As I measured in a previous blog post, the CM6631A appears to have just as low jitter whether with coaxial or TosLink.

2008 MBP to CM6631A to AUNE X1 (TosLink):

2009 MBP to CM6631A to AUNE X1 (TosLink):

Acer Aspire to CM6631A to AUNE X1 (TosLink):

ASUS Taichi to CM6631A to AUNE X1 (TosLink):

Notice how the jitter spectrum looks almost identical now just as the RightMark measurements above look essentially identical in each case with the CM6631A. With TosLink galvanic isolation, the Aspire's noise floor is in line with the others and in each case, the jitter modulation signal is well defined, again proving that Decibel (sending to the Mac's native USB 2 Audio driver) and foobar2000 (using the C-Media ASIO driver now) are capable of bit-perfect output when the hardware allows.


1. Even though most laptops/motherboards these days advertise their audio hardware as "HD Audio", they are generally nothing of the sort. Although the MacBook Pro's showed good dynamic range in the RightMark tests at 24/96, the 2008 model was incapable of true 16-bit processing. Likewise, neither of the two Windows 8 laptops were capable of preserving the 16-bit LSB jitter modulation pattern. Perhaps obvious, but the bottom line is that you cannot trust the built-in DAC's for even 16/44 resolution audio.

2. Watch out for noise creeping into the DAC from the USB interface as shown with the Aspire-X1 Adaptive USB example. This can originate from internal electrical components as in this case or other times ground loops. Galvanic isolation with the TosLink interface is one way of dealing with this.

3. Overall, the asynchronous USB interface is better than adaptive isochronous USB for jitter in this example (obviously I cannot vouch for all asynchronous DAC / interfaces). This has been demonstrated before already and seen again here. These days it's a moot point since asynchronous USB interfaces are readily available and if your DAC doesn't have one, just grab an inexpensive converter like the CM6631(A) I used here. There are of course some very expensive USB-SPDIF adapters but given the CM6631A results, why spend more from a sonic perspective? As I have also stated before, I still have no good evidence to say that jitter at this low level is ever audible with real music despite what subjective audiophile reviewers or Internet posters generally claim! In ABX tests and even non-blinded flipping between measured jittery vs. clean audio sources, I cannot tell the difference at least up to ~2ns peak-to-peak jitter; nevermind the usual few hundred picosecond jitter with decent modern gear [Ed. apologize for the error...  I previously had a typo of "2ms"]. It's possible that my ears aren't sensitive to this but to be honest, unless one has superhuman hearing abilities, I can't imagine how it would be physiologically possible given these test results.

4. If you keep electrical noise/interference at bay, and use appropriate software player & drivers to ensure bit-perfection, there is no reason why Macs vs. Windows vs. ANY computer would 'sound' any different paired to a good DAC. As you can see above, when the CM6631A asynchronous USB-to-SPDIF converter is used and galvanic isolation is in place, there's essentially no difference in the analogue RightMark measurements and the Dunn J-Test spectra irrespective of CPU, speed, memory, HD/SSD, OS, USB, etc. (obviously as long as the specs are good enough for bit-perfect output - this is the beauty of digital). (Here's another interesting article showing identical Mac vs. Windows output using JRiver and different methodology.)

I hope this article has been useful in demonstrating a few things about computer audio. Measurements allow an opportunity to verify claimed improvements and demonstrate technical progress in hardware performance - amazing that few audiophile magazines / web sites actually include independent objective measurements and reviews come out looking like infomercials and PR. Realize that none of what I've shown is all that mysterious or requires audio "voodoo" whatsoever - science is all you need; let the musicians provide the passion and art. The cables are all generic, reasonably high quality (ie. nothing looking like they're going to break!), and universally costs <$20 for standard 3-6' lengths. The AUNE X1 DAC can be bought off eBay for ~$200. The CM6631A USB to SPDIF costs $50. The analogue and jitter measurements are on par with much more expensive gear I've come across. No need to further obsess over details like jitter or bit-perfection because the objective data has set the mind at ease...  If this were my main listening system, this then is where I would start more subjective evaluation with the amp and speakers asking myself whether I prefer the sound of the technically accurate setup or not. Realize that not everyone wants technical accuracy - terms like "clinical" or "sterile" impart this pejorative connotation. IMO, there is no such thing as a system being "too resolving", there's only source material that's "not good enough"!

After all this, you might ask: "So how does it sound?"
     Great!  (No need for superfluous adjectives.) Now go enjoy some music...

For posterity, a response I put up on Audio Asylum questioning the results (April 21, 2013)...

I appreciate your feedback and critique. I used to have the QB9 and indeed it is a nice DAC so was quite happy that Stereophile's measurements concurs.
For this article, I believe the data was "bit perfect" since the LSB jitter modulation was evident in the 16-bit tests. Due to the hardware limitations, this was of course not seen in the 24-bit graphs. I did discuss this fact and the issue that the built-in computer DAC's had problems with bit-perfection.

Thank you for bringing up the "skirt" issue. I'm going to have to update my ASUS Essence One measurements because this was worse with the USB input but not the coaxial or TosLink. However, most of what I've seen suggests that this low frequency jitter is masked by the primary signal. Please correct me if this is wrong so that I may pay more attention to it especially if there's a point of audibility.

As for "at some point you have to listen to the damn thing" (I'm directing this to the general viewership, not just to your comments). It is precisely because I've been listening AND reading forums like this for the last 15-20 years that I started doing the measurements and putting up the blog! I don't think it's at all a stretch to say that people are notoriously unreliable in their experience... I have never found an audiophile who could reliably differentiate high bitrate MP3 for example, yet when I ask, everyone seems to say they can (sure there are people who can ABX 320kbps but that's very few). For those who have a copy, listen to track 26 on Stereophile Test CD2 simulating 10ns jitter. I would estimate that half of the audiophiles I've tried this on over 50 years old have difficulty hearing this simulation on a test tone yet they universally claim that a few hundred picosecond jitter is a "problem" audible in actual music.

There's precious little objectivity out there anymore for audiophiles - look at that bizarre 3-part article on computer audio in TAS early 2012; if "everything's possible" (bit-perfect rips sound different if ripped at different CD speeds according to that article) then nothing is known anymore. Just look at the numerous comments when those new to computer audio asks straight forward questions here. IMO, some of the responses border on delusional.

Time is limited but I have spent many many hours listening to cheap to very expensive gear - even owning a few of the more expensive items over the years. It is my belief that "good" sound can be independent of factors like price, or any of the external factors like workmanship, etc. In fact, I've come across situations where high priced gear are just plain inaccurate. For me, accuracy is all that matters, and this can be quantified objectively.

Speaking of "misinformation is what is sending most people into shock when they start CA". Realize that over these months of testing, I have not advocated anything I would consider as "fringe". I've shown that asynchronous DAC's are better with less anomalous J-Test spectra, coaxial and good USB is better than TosLink in the gear I have, shown 'good' DAC's like the Oppo BDP-105 (ESS Sabre) measures superbly. I advocate for "bit perfect" and showed that both Windows and Mac are capable of accurate output, and have interspersed these tests with listening to make sure nothing appears awry - usually spending a couple hours at a time in the evenings listening (eg. when I was doing some cable measurements recently). As I've said in some posts, there is no voodoo or magic here, and the tests are showing me such. How in the world is this shocking anyone out of computer audio!? If anything, it's reassuring that measurements line up with a rational empirical approach that is reproducible.

Now as for the test gear I use and software like RightMark. You don't need the Hubble telescope to identify Jupiter in the sky. Likewise, why do I need expensive gear like an AP when I just want to make sure the frequency response is relatively flat, or that the dynamic range of a DAC can exceed 16-bit CD quality, or that the Dunn test isn't atrocious? All these things are within reach of what I have and the beauty of computer audio and technological advancement is that stuff that can do this is easily within the consumer's grasp. However, I'm not saying that anyone should do this since it has taken me countless hours to learn how to get the calibration right and make sure the software setup works for me in order to achieve a high level of reliability in the measurements.

When my simple setup can easily demonstrate analogue cable differences, XLR vs. RCA differences, show me the spectral smearing between 320kbps MP3 vs. 400kbps AAC, demonstrate J-Test differences between coaxial vs. TosLink vs. AES/EBU, when I post about this, in what way is this "misinformation"? In fact, my ASUS Essence One measurements showed a disturbing anomaly when upsampling is used resulting in attenuated frequency response which has since been confirmed by ASUS (and hopefully to be remedied)... How come subjective Essence One reviewers missed this when it was so obvious with just a little testing?

Look guys, ultimately either what I say and write about makes sense, or it doesn't. I mention a new post up here once awhile that could be of interest like this one with the laptop tests to outboard DAC's. I have ZERO financial interests or otherwise. I do it for fun, for my own education, and enjoy sharing what I've found with others. Anyone can freely share their thoughts in the comments section (haven't had to censor anyone at this point for nonsense), and I've invited people to give me evidence/reason if they think something I say is wrong. Of course, with my objectivist mindset, "Level 4 or 5" evidence (ie. individual or series of reports) doesn't really impress compared to experimental results or controlled trials.