Saturday, 29 July 2017

REVIEW: SMSL A6 integrated amplifier - Part I: Overview and Subjective Listening (and briefly about USB cables)

SMSL A6 at home in my living room system with Tannoy Mercury Mx2 speakers. Doug MacLeod's Break The Chain (2017, Reference Recordings 24/176.4 downsampled to 88.2kHz, DR16) playing over Logitech Media Server.
For many years, my father's audio system consisted of various CD players, a Sony turntable and vintage pre-amplifiers. This then fed a tube pre-amp which then sent the signal to either a tube-based Onyx SP3 Melody amplifier or vintage solid state Pioneer amplifier to feed his Klipsch Forte speakers which have been cleaned and refurbished with new crossover parts over the years.

In the last 5 years, I've supplemented his system with various DACs for the CD player, and most recently got him a streaming connection with my Logitech Media Server based out of my home server using a Logitech/Squeezebox Touch.

This set-up sounds very good. The classic Klipsch speakers really do throw up a fantastic soundstage, have quite a smooth sonic signature (though a little mellow for my taste), is extremely sensitive, thus easily powered by low-wattage amps.

He has gradually transitioned to almost exclusively digital streaming, finding the convenience indispensable compared to spinning disks (whether of the polycarbonate or vinyl variety). As much as the tube and large integrated amps sound great, over time some of those components have needed maintenance and I figured it would be nice for him to try out something much simpler than manually turning on/off multiple devices every time he wants to hear good sounding audio. Thus, the purchase of the SMSL A6 integrated DAC/amp.

After the positive experience with the company's iDEA DAC a few months back, I figured I'll give this a try as it seems to fit his needs (plus Amazon has its usual 30-day easy return policy). At ~US$450 it's certainly not expensive for the features listed and with a phono input and separate analogue line in (for CD), he can hook up his whole system without fuss.

I. Physical Characteristics

Let's have a peek at the device:

The image above to the left is the box contents with the integrated amp, manual (surprisingly detailed compared to many other items from Asia), a short IEC power cable, generic USB cable, driver CD, and of course the remote. I show a close-up of the remote to the right. The remote feels quite good in the hand - metal construction with good weight, rubberized action on the buttons.

It seems that this remote must be a "universal" remote of sorts for SMSL products. The "A", "B", and "C" buttons seem to select different devices with the "A" assigned to the integrated amp. If you seem to have trouble controlling the device, make sure you press the "A" button first just in case someone had pressed B or C.

The prominent power button brings the device out of sleep when plugged in. The multidirectional ring allows volume control (up & down) and the various inputs (left & right). The center button toggles between various settings (including the color of the main text on the LCD screen - the "white" setting looks good). The button to the right of "A" with the arrow pointing down into a round icon is the input selection toggling between USB, the various S/PDIF options, analogue CD input and PHONO. "EQ" allows various settings like DIRECT, SDB, and TONE. DIRECT is without processing, SDB refers to "SMSL Dynamic Bass" - their bass boost system, and TONE allows manual +/-9dB gain in bass and treble. As you may suspect, unless specified otherwise, I stuck with DIRECT.

As an IR remote, it has to be line-of-sight +/-30-degrees from mid-line and SMSL recommends within 7m distance. As usual, I'd probably program the device into a learning universal remote if I were to keep it in my system.

Front panel is basic and non-flashy (good!). The centrally located LCD screen which can be seen in use above measures 1"x 1" which is small from a distance but the input selected (eg. "OPTI" for optical) is displayed with a larger font. You can change the color of the main text if you want (white, red, green, blue, yellow, purple). The LCD brightness isn't high which may make visibility more difficult in a bright room but for nighttime listening the setting is just fine and absolutely unobtrusive especially with a darker color like blue for text color.

It has 2 knobs - the left one allows you to toggle between menu items and settings. The right knob is the on/off switch when pushed down for a few seconds. When it's on, a quick click down mutes the device and rotating the knob acts as volume control.

You can also see the headphone output on the front. As with most devices, it will detect the presence of headphones in the socket and mute the amp while in use.

Here's the back. Standard IEC power connector. Right / left binding post output to the speakers - I just used locking banana plugs. A collection of 3 digital inputs - asynchronous USB, S/PDIF TosLink and coaxial. Then there are a series of analogue RCA's - line level output from the DAC if you want to use your own amplifiers, analogue (CD) input, then analogue phono input with accompanying ground lug to the far left.

No fancy features like network input, WiFi or Bluetooth. It's designed as a no nonsense integrated amplifier and quality DAC.

I found the metal enclosure sturdy and the device has a solid feel to it. It weighs in at less than 5 lbs which means it's not going to strain any actual bookshelf you might want to put it on. Notice that the exterior has a matte black consistency to it. While I prefer a bushed metal look, at least it's not highly reflective but it can be harder to keep clean when fine dust or oily fingerprints get on the surface.

As you can see in the image up top with the Logitech Touch sitting on top of it, it's quite a compact device measuring ~8.5" x 7.9" x 1.75" (21.5 x 20 x 4.5 cm). 

II. Features & Internals

Like with the iDEA DAC, SMSL isn't shy about telling us what's in this device on their web page. I see this as a good thing as a "more objective" audiophile. Although just knowing the components themselves will not tell us how well the device is implemented, it does give us an idea of expected capabilities and potential quality.

On the DAC side, they're using the Asahi Kasei AK4452 converter, a recent ~2015 "Premium DAC" with the capability of receiving up to 768kHz PCM and DSD256. Although there are no filter settings with the A6, I see that the chip itself does have a few options available to choose from. My assumption is that the default filter is a sharp roll-off settings which the datasheet describes as performed in 32-bits with 8x oversampling (we'll have a look when I run some measurements).

Although the official DAC chip specs say DSD256 "input maximum", SMSL has allowed DSD512 input through the CMedia CM6632A asynchronous USB2.0 audio interface. Like with the iDEA, whether DSD512 is an undocumented setting or if there is some downsampling going on, I'm not sure. In any event, I have long used the CM6631A USB to S/PDIF interface since 2013. Given how well jitter was controlled back then with the older iteration of the silicon, I anticipate that timing will not be an issue here either.

For the headphone side, the Maxim MAX9722A amplifier is used here. The datasheet describes this as capable of ~130mW into 32-ohms <0.02%THD+N at 1kHz. Looking at the graphs, it drops to about 55mW into 16-ohms <0.1dB THD+N. They call it "DirectDrive" - no DC-blocking capacitors necessary. Clearly not the most powerful headphone amp, but probably adequate for most users.

I've got my 1MORE Quad Driver headphones plugged in playing Imagine Dragons' Night Visions. Notice on the front screen that it's using the "OPTIcal" input, headphone volume at 14 (out of 40), PCM 44.1kHz input. My digital camera accentuated the brightness of the LCD screen. In use, the background is clearly dimmer than the picture.
Finally, as advertised on the front, this device uses an ICEpower amplifier. ICEpower 50ASX2 Class D amplifier to be exact. ICEpower as an OEM provides amplifier boards for many companies and is 100% owned by Bang & Olufsen since 2008. This specific device is rated as 2x50W into 4-ohms, 1% THD+N in the audible spectrum both channels driven. At 8-ohms, it's rated at 25W with 1% THD+N.

As you're likely already aware, Class D "switching" amplifiers are much more efficient than typical Class A and A/B amps. They use less total power for the same output and dissipates much less heat. In standby mode, the A6 uses <4W. Turned one for more than an hour, the A6 case will warm up slightly, but stays notably cooler than my ASUS XONAR Essence One desktop DAC. If you examine the enclosure, there are no cooling vents anywhere.

III. Subjective Sound Quality

As usual, I will run this device through a test bench in the weeks ahead.

For now however, I can say that this device does work well and sounds very good. Since I bought it for my father, he was quite happy with the flexibility and ease of operation. Without fancy network operation or other complexities, you just plug in your devices and speakers, select your input and away you go with the convenience of the remote control. Plug in, press the "on" button, and he's ready to play in a couple of seconds (no long boot sequence like some devices these days!). My father likes the typical audiophile female vocals genre so music like Cai Qin's (蔡琴) Collection is right up his alley. No concerns at all matching the A6 with his classic Klipsch Forte speakers. They're efficient with a sensitivity of 98dB SPL/W at 1m, 8-ohms, so the 25W rating is just fine for listening in a moderate sized room. Excellent imaging with the front-and-center vocals. Backing instruments sounded clean. I know some people complain of Class D amps having a sharp "sheen" or adding a "glare" to the sound. Certainly with these speakers, to my ears, there was no problem with the pairing whatsoever... Although A/B'ing takes a few seconds switching cables, the sound is comparable to his Class A/B Onix SP3 integrated tube amp which was a lot more expensive a number of years back.

I must admit that although the Klipsch Forte speakers are fine for the mostly vocal and acoustic music my dad listens to, they seem lacking in treble extension for my taste. Note that this is subjective since I've never taken my measurement mic to his system and may be just a reflection of his room acoustics rather than the speakers. Nonetheless, I did enjoy the recently released live Paul Simon The Concert in Hyde Park (2017, 2 CDs, around DR10). I've always liked the sense of spaciousness of the Klipsch sound and a live recording like this really brought out the energy of the concert!

For a more familiar comparison, I took the SMSL A6 home and downstairs to my main listening room... As a size comparison, just have a look at how small this device is compared to my Emotiva XPA-1L monoblocks, Emotiva XSP-1 preamp, DAC and speakers sitting on top of the Technics SL-1200 turntable!

I hooked up the Raspberry Pi 3 Touch player via USB to the SMSL A6 input for a listen. The Raspberry Pi 3 had no issues detecting the A6 using piCorePlayer. As usual, select the proper USB input:

Subjectively, I'm sure it will come as no surprise that a modern Class D amp sounds good. What is noticeable of course is the fact that we are looking at a 22Wpc (into 8-ohms, 0.1% THD) amplifier here compared to my 250W (into 8-ohms, 0.1% THD) Emotiva XPA-1L monoblocks! Although the Paradigm Signature S8v3 speakers are reasonably efficient at ~92dB in room, when I run DSP room correction which applies a bit of attenuation, at 100% volume on the SMSL A6, the volume is loud but certainly not intolerable in my room of about 15' x 20' x 8' size. I have never pushed the XPA-1L monoblocks to 0dB on the preamp in actual listening; that would just be painfully loud and subject one to premature hearing loss!

Apart from the expected power limitation, the only thing I thought I noticed was a little more harshness in some of the compressed pop/rock music. For example, listening to the recent Coldplay & The Chainsmokers tune "Something Just Like This" (off Memories... Do Not Open, 2017, DR5), the vocal sibilance was a bit harsh compared to the monoblocks. Though I would not consider modern pop audiophile fare, I figured it was worth noting.

High quality recordings sounded great - Doug MacLeod's Break The Chain (2017, DR16) is a good example of a modern hi-res recording with great dynamic range, lots of detail and nuance for those into straight-up blues. The recording BTW was done by "Prof." Keith O. Johnson at Skywalker Sound with the CD release apparently still encoded as a HDCD (even in 2017). Great lyrics, performance and sound quality on the title track for example. Beautiful how the instruments just "hang" in the atmosphere enhanced by the natural sounding percussion section.

Something I liked about the A6's USB input is that even when switching between different sources, the USB connection remained intact from the perspective of the streamer. On some DACs like my TEAC UD-501, when I switch out of the USB input, the device will disconnect from the streamer or computer. Not so with the A6. I can switch between the different inputs while playing from USB and the streamer won't skip a beat.

The inclusion of a phono input makes this device also attractive for those who might also have a turntable in the system. I attached my Technics SL-1200M3D with Denon DL-110 HOMC cartridge into the phono input and playback sounded "full bodied" and very pleasant (remember, my opinion is that vinyl isn't capable of true high-resolution so I tend to accept the idiosyncrasies and enjoyment is good enough without needing to be too analytical with the sound extracted off the plastic grooves). An early pressing of The Beatles Abbey Road, Springsteen's Born To Run, and Daft Punk's Random Access Memories from a few years back served as familiar evaluation material. The RIAA compensation sounds good enough to me. Although not explicitly noted, you will need a step-up transformer for low-output moving coil cartridges. The manual did not provide any details on phono impedance matching so I assume it's expecting standard MM cartridges with characteristic output voltages ~3mV and 47k-ohm input impedance (and my Denon HOMC sounds great plugged into this).

IV. Impressions

Years ago, when I was in university, I used a Sony integrated amp which carried me through many years of college life. I imagine these days with music on computers, with streamers like the Pi 3 easily constructed for cheap, if I were a student with limited budget but want really good sound, a device like this would fit the bill. Pair this with passive (good but inexpensive) speakers like maybe ELAC, Wharfedale, Pioneer, Paradigm, Tannoy, PSB, KEF, Mission, etc. bookshelf models and the audio quality will more than likely be excellent. In fact, because I believe "good sound" is primarily a function of the speakers and room, the bang-for-the-buck is to save money with the DAC / amp / streamer side of things while putting more of the cash into your speakers. Given the size, I imagine the A6 would also be a good desktop computer audio workstation system with passive speakers functioning as a very feature-filled PCM/DSD DAC.

On the other hand, as I mentioned at the beginning of this post, the reason I ordered this device is for my father. Even though he has enjoyed hi-fi sound for years, there's something to be said for simplicity and convenience! I see it as "downsizing" but without really paying a terrible price with reduction in sound quality compared to what he's already using. Even better is that this device is much more efficient which keeps it cool in the summer, and saves a few dollars in energy costs (Class D is much more environmentally friendly, right?). So far, my dad thinks very highly of the convenience and sound - calling me a few times as I currently have the device for testing, wondering when he can have it back :-). Thus easily achieving the goals of the purchase in the first place.

Remember that there are quite a number of options out there when it comes to small integrated amplifiers like this with DAC functionality. For example, there are the inexpensive Onkyo A-9050 (75Wpc into 8-ohms, a little larger, US$350), NAD D3020 (30Wpc into 4-ohms, Bluetooth aptX, US$400), TEAC AI-301DA (same ICEpower 50ASX2 amplifier as the A6, US$400) and PS Audio Sprout (32Wpc into 8-ohms, US$500) around the same price range as this SMSL A6. Higher up in price we have the NAD D7050 (50Wpc into 4-ohms, network streaming, US$800), and the ELAC Element EA101EQ-G Integrated (US$700, 2.1 channels, 80Wpc into 4-ohms). Even higher up the price range, one could look at the beautiful Marantz HD-AMP1 (US$1100, 35Wpc 8-ohms, 2.1 channels), Peachtree nova150 (US$1800) and nova300 (US$2500). The Peachtree novas are using higher power versions of the B&O's ICEpower amps internally. Each device will have varying features like a remote control, number of digital inputs, Bluetooth, phono input for turntables, samplerate & DSD capability, headphone output quality, etc... Important to do some research to find the right features for your needs.

Since this is my first time writing about and testing a product like this, I figure it'll be interesting to take my time and explore a few of the functions to see how well a US$450 device like this in 2017 works objectively. Next up we'll have a look at the quality of the DAC output with the AKM AK4452. In the next few weeks, I think I'll also spend some time measuring and comparing the output of this Class D amplifier with other amps I have around here. Stay tuned...


Did Digital Audio Review close off the comments section about a week and a half ago correlated with a series of questionable, if not a little paranoid articles about USB cables, power products, and even more words spilled on USB cables? I suspect those articles would have garnered quite a number of responses and many more reads if people were allowed to comment. As for the gist of that latter article, realize that objectivists typically seek to understand what devices can influence the sound the most. Speakers are much more complex and most will appreciate that it's not unusual to hear differences. Amplifiers can have their own sonic signature with variation in frequency response, harmonic distortions, clipping behaviour, ability to drive demanding loads, etc... This is why reviews can sound very plausible and typically not terribly controversial when it comes to things like speakers and amps. But USB cables??? 

Suppose a friend called me up after a hike in the woods describing how she saw a grizzly bear along the way (grizzlies of course live in this part of the world). That would certainly be very interesting and worth discussion. But what if she claimed that she saw Sasquatch/"Bigfoot" (also supposedly living in this region of the world) on Facebook? Would it not raise a few eyebrows among friends? Create more chatter? Even suggestions that she may have been mistaking a bear for the mythical creature? So too, unlikely claims made by typically purely subjectivist reviewers about audible benefits of expensive cables will tend to stir up more controversy. No surprise.

I'm happy to admit that jitter does happen - but inconsequential with any decent asynchronous DAC these days and standard length cables cannot affect the DAC's jitter performance anyway. I'm even happy to demonstrate what audible distortions sound like due to data corruption by a very poor cable. But where is there evidence that any expensive USB cable sounds better. Where is there even a logical explanation for alleged profound changes to tonal balance, apparent amplitude, soundstage differences reported by various reviews over the years? Digital transmission is well understood and brings with it various self-evident truths about what is and what is not possible. This is not only from a theoretical framework but also in real-life practice! If this were not so, how would we even be communicating with such reliability over the Internet? How can we be streaming lossless audio with such high quality (Darko uses TIDAL right?)? How could Netflix be streaming 4K video at 15-30Mbps with multichannel sound over thousands of miles, likely switching between optical and wired cabling without deterioration if we can't even get audio transmission right over a few feet using a USB cable (BTW, only 1.4Mbps lossless CD, 4.6Mbps 24/96, 9.2Mbps 24/192)!?

As for this beautiful nugget:
"But wait. If xxxxxxxx and yyyyyyy are on the opportunistic take, it follows that every USB cable manufacturer is a con merchant; that reviewers of their products are also shills; and every owner of an audiophile-grade USB cable has be duped proving that a fool and his money are soon parted. Hundreds of reviews and thousands of end user comments – all lies."
(Names removed to protect the "innocent".) Please, why so dramatic - "con merchant", "shills", "duped", "fools"? First, there's nothing wrong with taking opportunities. That's inherent in capitalism - go ahead and satisfy the demand and profit from it. I write this blog, I turn on AdSense, I make a few bucks if readers find the topic interesting and the ad catches their attention. The question is at what point does the taking of opportunities cross the line and become immoral? Pharmaceutical and nutritional supplement companies take advantage of opportunities to sell a product all the time even if benefits may be marginal or practically insignificant - at what point do marginal benefits become fraudulent claims? Dr. Oz promoted "miracle" pills; doesn't he still have a good sized following? How many millions (even billions) of people have strong faith-based allegiances to horoscopes, miracle healers, psychics, and countless spiritual organizations? Some individuals might be lying, some might be opportunists, some might be psychotic, some might truly find benefit in different ways. If you ask the "faithful", many will recall experiences which they believe "prove" their faith just as some in the world of audio have "heard" a $5000 USB cable sounds better to them than a $1000 one.

I'm certainly not saying that faith does not have a place in this world. I actually believe the subjective world is extremely important; but that's another broader discussion. However, when it comes to electronics, digital communication, and USB cables, the "hundreds of reviews and thousands of end user comments" are certainly NOT "all lies". Expressions of faith may be genuine, even if ultimately mistaken when the belief is explored under controlled conditions. And yes, IMO some out there are just liars, or complicitly "toe the party line" based on financial motives - let us not pretend to be naïve, as if it could be any other way in the face of the profit margins for selling "high end" wires!


I just want to end this post with a shout out to Mitch Barnett (aka Mitchco on Computer Audiophile) for his hospitality last weekend when I went to visit him at his place at the beautiful Sunshine Coast (alas it wasn't particularly sunny that day)! It's great when the joys of a hobby develops into relationships with fellow "travelers" on this journey. Thanks for the beverage, sushi and discussion of topics far wider and deeper than just sound reproduction... :-)

I hope everyone is enjoying the music. Remember to listen to the MQA Blind Test and keep the survey results coming! Another month to go...

UPDATE (Aug 5, 2017): SMSL A6 Measurements - Part II - exploration of the DAC objective performance and a bit about the headphone output is now up.


  1. I bought a SMSL SA-50 (USD$60) in 2014, a very simple speaker amp with only power switch and volume control. Superb build and sound quality with no sign of ageing apart from some rusted screws until now.

    Even though USD$450 seems inexpensive for a device at this class, the A6 is supposed to be one of the most expensive SMSL product ever, it cost about $USD350 in China though. It seems that SMSL is becoming more and more famous over these years, just hope it won't become one of those snake oil brand some years later.

    1. Hi Dtmer,
      Thanks for the note. That's a great price in China. Admittedly I have not looked at the catalog of hi-fi from SMSL so it is interesting to know that the $450 price is one of their most expensive products... As you say, in audiophile world this is not a big price tag compared to so many others!

  2. Hi Archimago, I'm glad you also noticed that John Darko shut down user comments on his blog when posting the recent bizarre articles defending his glowing articles on audiophile snake oil. My favorite comment was:

    "Let us also ignore that differences between USB cables are measurable."

    He links to a posting about how Gordon Rankin has measured bit errors in audio USB transfers. Now of course Gordon Rankin designed Audioquest's DACs, so he works for a company that markets $1000 USB and Ethernet cables. No conflict of interest there! And of course we've actually never seen any error rate analysis of Audioquest's "audiophile" cables on their web site, because of course this is all BS.

    What's interesting though is the tide is starting to turn. Darko had to turn comments off on his postings, because he knew he'd be bombarded by comments from educated readers who knew his glowing reviews of this stuff is because if he didn't he'd be out of a job. If you look at some of the comments from recent articles/reviews on The Absolute Sound you will see the same thing - people are becoming fed up with reviewers posting glowing reviews of $1000 digital cables and other equipment that has no reason to exist.

    So is this a conspiracy, as Darko is questioning? No, it's simply a small number of people who make their living from writing about audiophile equipment, and the only way to do that today is to cater to your advertisers. Mostly high-end manufacturers, and in this world, the more expensive an item is, the better the review needs to be. No glowing reviews of Belkin USB cables in this world.

    Clearly from Darko's recent articles, and the closing off of comments, he's seeing that people are getting smarter and better educated about what matters in terms of audio quality. Michael Lavorgna at Audiostream deals with this by cancelling people's accounts who question the logic and motivations behind his bogus reviews.

    At least I saw a review of the Schiit Yggy DAC (I own its little brother, the Modi Multibit) in the Absolute Sound by Robert Harley recently that summarized its quality as "its one of the three best DACs I’ve heard regardless of price. (The other two are the $19,500 Berkeley Alpha Reference and the $35,000 dCS Vivaldi....". And Schiit doesn't advertise in any online publications as far as I know. So some progress is being made, and I expect the trend will continue as audiophiles become more educated about digital audio and what does and what doesn't make a difference in sound quality.

    1. My sentiments exactly Jim.

      I can't speak much more about DAR since I don't visit there regularly - I simply did last week because of some MQA-related posts, and was surprised by the lack of lively comments.

      As for AudioStream. All I see are a bunch of music recommendations, teaser articles with little detail, some strange articles off the mainstream, and the occasional hardware review. Good to see in any even much less bizarre claims compared to yesteryear.

      As with most things in this world, it all runs in cycles... Maybe the purely subjectivist audiophile mindset will give way to the pendulum swing towards objectivism with actual knowledge, understanding, and rational discussion around the physical principles of the equipment we buy and use. IMO there's also something to be said about the pendulum swinging too far to the other side but we're far from that at this point!

      Yeah, I saw the Yaggy DAC review. Good to see even though I've not heard the Schiit products and never been a fan of TAS.

  3. Archimago,

    I am glad you are opening up discussion on the DAR article. I am one of those who felt like commenting, but DAR doesn't accept comments.

    I too am a bits-is-bits kind of guy and see no possible reason data carried over USB should depend on the cable used. Your measurements verify this. But, I have actually heard a difference. Before you wave me off as a subjectivist kook, let me back up my claim with a possible explanation...

    I have tried 4 or 5 different USB cables to connect my Squeezebox Touch to my Burson DAC/Headphone amp. As expected, I heard no difference. They were all of the "generic" variety, a couple came with old printers. The thing is, in my setup the cables are quite visible and the cheap cable looked kind of like I didn't care. So when I saw that Wireworld sold an "audiophile" USB cable for only $23 I decided to get one. Mind you, this decision was based on purely cosmetic reasoning.

    I hooked up my new cable, played a few things, and as expected did not hear a difference. That is until I played the third movement of Beethoven's Piano Sonata #23 "Appassionata" played by Lylia Zilberstein (96/24 download from HDTracks), a piece I am very familiar with. Towards the end of the movement, when she is pounding those chords for all she's worth, there was noticeably less high end "breakup" apparent. The piano sounds were smoother, less clangy. I had thought my setup sounded pretty good with the generic cable, but this was better. And re-installing the generic cable caused the distortion to return. The improvement with the Wireworld USB is not subtle, I believe that any astute listener would easily hear it. And it is definitely analog distortion, it doesn't show the characteristics of digital distortion.

    So, why was this? My assessment is, the Wireworld cable physically separates the data-carrying conductors of USB from the power-carrying ones. My other cables were all of a coaxial construction. My Burson DAC (even though it is self-powered) requires that the USB 5 volt current be present to work. So I'm thinking that with the coaxial cables, the "perfect" music data stream is interfering with the stability of power circuit and that some component on the analog side of the DAC is misbehaving and causing the distortion.

    Notice here that I am not talking about ethereal audiophile things like soundstage width, "air" around the instruments, or imaging. This is about just plain less-distorted musical sounds. I do not hear changes in any of those audiophile touchpoints but I also don't see any reason, if the distortion is caused by USB power corruption, why it couldn't affect these other analog "distortions" too. I would guess that many other "better" USB cables also isolate data from power. And that various DACs do or don't use the 5 volt current. And that some DACs would be less sensitive to power fluctuations. Could this explain why many enthusiasts are adamant that USB cables affect sound quality while others hear no difference? Is this something that has been measured? Can it be measured?

    Then there's Ethernet cables. Do you think I should I get better ones before participating in the MQA Blind Test? Just kidding. Despite my USB experience I am still a bits-is-bits guy, it just seems that there may be more to it.

    P.S. The new cable sure looks good and does make me feel like a better audiophile.

    1. Interesting comments. It would be great if you could make a recording of the passage with the two cables to demonstrate the difference.

    2. Thanks for the perspective and anecdote Mark.

      Don't worry, I don't wave people off who take the time to explain themselves so well as a "kook" :-). (Nor do I ban them with their thoughtful expression of experience!)

      So the theory is that the 5V power lines are somehow being affected by the data lines or vice versa. Now here's the part that we need to explain...

      1. Why is it happening with the 24/96 music and not 16/44 presumably? (Did you downsample the 24/96 Piano Sonata to 24/48 for example and listen to hear if there was a difference between the 2 cables?) If this does NOT affect 24/48, then are we saying the data rate has something to do with it?

      2. Why is it happening with the louder passages? Is the distortion / strain happening only when the DAC has to put out higher voltages to the preamp/smp? If so, how is there a correlation with the USB cable itself rather than perhaps an issue with the DAC?

      I agree with Robert Z as a first step. If it were me, I would for sure hook up my ADC to the DAC output and record the passage with the generic USB vs. Wireworld (you got a great deal on a product that looks good, so clearly you got your money's worth). Make sure to document the difference. From there, figure out what's going wrong with a few tests such as trying different sampling rates, etc...

      If you do record this difference, definitely let us know! Would be great to listen to the recorded passages to help diagnose the problem.

    3. I had a similar experience in listening to music via iTunes vs. Audirvana. I was not expecting to hear any difference at all between two bit perfect players in bit perfect mode but I ran across several instances where there was noticeable distortion in iTunes that was not present in Audirvana. It was not noticeable 99% of the time, but where there were issues, it was clearly audible and repeatable.

      There's probably an explanation for it (e.g., iTunes through Core Audio vs. Audirvana in "integer" mode, etc.), but it just shows that sometimes there are other factors at play that are not immediately obvious. Just like the current discussion around USB cables - it seems to be coalescing around total agreement that there is no significant issue with passing data perfectly (dropped packets or the equivalent are virtually non existent in a properly performing environment) but acknowledging that power line noise can be a significant influence to the DAC which can be ameliorated with appropriate filtering or galvanic isolation.

    4. iTunes is not bit perfect. And if Core Audio has a híckup weired things will happen. For things like this a tech with some knowlegde quickly finds the culprit and might even fix it. Problem is that most people don't even start to find the cause of the differences, but quickly jump to the usual conclusions (bit perfect - still sound differences exist...).

    5. iTunes *is* bit perfect if configured correctly and you know what you're doing ;)

      I was just pointing out that what may appear, on the surface, to be a "bits is bits" situation may, upon further investigation, have other confounding factors that are not immediately obvious - so it's best to acknowledge "bits is bits" but not be close-minded about it.

    6. Yes. But iTunes was not bit perfect in my tests. When I tried 24 bit a few months ago with all sample rates, not only 44.1/48, it failed (I should recheck this with the latest macOS version, though). The problem might be the underlying Core Audio. I did not spent more time to check this as I don't use Macs to listen to Music. It was able to handle 16 bits in all rates.

    7. Archimago
      Thanks for your response. I am intrigued by your suggestion that I attempt to record what I'm hearing but I have two concerns:

      First - My "ADC" would be the motherboard soundcard on my PC, which has only a microphone input. It seems there could a bad mismatch feeding the headphone output of the DAC/headphone amp to a mic input. In the past I have have always experienced unacceptable sound quality when recording using anything but line-level to line-level. In your opinion is this worth trying? If you think it is, I am game to give it a go. (I guess my smartphone has an ADC also, but I'm sure I don't have the required 4-conductor mini phono plug to feed it.)
      Second - Just after my initial post I updated my LMS and Touch to install the new "Spotty" plugin in order to continue using Spotify. Well, something in the EDO plugin went haywire and now I have no USB output. Selecting USB mode freezes the Touch screen and there is no sound. Days of reinstalls, reboots, firmware updates, help from the Squeezebox community, and much hair-pulling have not yet solved the issue. With my DAC the USB sounds better than either the coax or Toslink so I am at wits end. (If anyone reading this has a fix, I'd appreciate any help I can get.)


    8. Hi Mark... Oi.

      I feel your pain regarding the LMS/Touch/EDO issue. That sucks! I hope you get it working soon.

      With regards to recording the sound... Hmmm, alas if all you have is a mic input on the motherboard, this will be an issue. I guess it really depends on how much difference / distortion you're hearing. If there is a *huge* difference then it might be still possible to pick up a change but otherwise, I'm afraid you'll likely have to maybe borrow a better ADC with line level input.

      In any event, if at some point you manage to record the difference, then please let me know and I'd love to have a listen/look at the recorded files!

  4. "The question is at what point does the taking of opportunities cross the line and become immoral? ... - at what point do marginal benefits become fraudulent claims?"

    Here ya go!

    "A legendary Shun Mook product now being made in a very, very limited number. This record clamp is made from extremely rare pieces of dried ebony briar. This extra heavy century old ebony root which were immersed in the swamps of Africa has a unique power that no other wood possesses. The vibration generated by the diamond stylus in the vinyl groove besides inducing an electroflux through the phono-cartridge also excites the ebony molecules, causing it to resonate. This in turn is feed back through the stylus and is reproduced as expanded sound staging, enhanced separation, sharpened focus and enriched tonal balance of the music."

    Yours for $3.2k. Immersed in the swamps of Africa indeed!

    1. Man, I couldn't stop laughing! Electroflux you say, the ebony "molecules" (what a joke!) are excited, this is snake oil to its finest!!!

    2. Ahhhh yes...

      The precious mythical and mystical century-old African ebony. Drenched in swamp water - the elixir of the gods of the First Men. Now imported and hand made by high priestess Katy Perry-like maidens (aka "Gurls"?) in the sun drenched New World, the promised land of California right alongside the tech titans and wizards of Silicon Valley.

      Clearly this is a product of the highest scientific, technical and spiritual order...

      Thanks for the smiles, Daniel. :-)

  5. The kicker is that it may actually make an audible difference with some turntables. (But of course, so would a clamp of similar size and mass made of inexpensive materials.)

    1. Hi Don,
      Yup, could make a difference since in the analogue world with such small mV signals from the turntable, all kinds of changes to the sound is possible...

      The problem is of course the claims, the cost, and ultimately the VALUE (or lack thereof!). I personally have nothing against African ebony and swamp water :-).

  6. Glad u mention Onkyo I have A 9755 a superb integrated amp with lots of power also D class

  7. Thanks for sharing the valuable points, i think it still works.

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  8. Hi Archimago, just found out your blog as I was looking for a review of the SMSL A6. Very interesting blog, compliments, of course I read the whole review of the SMSL (waiting for the 3rd part, 好期待!)as I'm looking for a replacement for my trends audio ta 10.2 (tripath based amp) since I sold my klipsch and bought the ELAC which have much lower sensitivity. I have seen on SMSL website that the A8 with the icepower 125asx2 is coming out soon, just asked them the price and spec by mail, waiting for their reply. May I ask you if you ever listened to the Nad D 3020 playing? (it s actually rated as 30W on 8-ohms, not 4, so it should have the same power but an Hypex module). I listened to the Cambridge audio Cxa 60 and I wasn't all that impressed (my Trends sound much better to me, with high-efficiency speakers I'd say no one could deny that) even if the press seems to love it (what's hi-fi) so I'm very confused. Looking forward to your last part of the review of the A6, if you have any suggestion for an amp (around the price of the two mentioned above) which would suit my Elac Debut B6 I'd appreciate!Thx!

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