Thursday, 28 August 2014

MEASUREMENTS: Technics SL-1200 M3D Wow & Flutter - PlatterSpeed + Dr. Feickert's Test LP...

So, I got the Dr. Feickert's Adjust+ 7" Test LP in the mail the other day direct from Germany. It looks well pressed on good quality vinyl.

It's great to see the measurement screenshots from Michael Fremer for the various turntables reviewed so I thought it would be interesting to do my own measurements with the Technics SL-1200 (M3D) here at home. I believe that all the Technics SL-1200 quartz-controlled direct drive units (MK2 onwards) have the same servo mechanisms so they should measure similarly.



I'm using the current PlatterSpeed iPad app (v.2.2) to do the measurements in concert with the Test LP.

Recorded over 60 seconds, here's how the wow & flutter graph looks for my Technics with the stock rubber mat in place and stock tonearm at 33.3 rpm. The turntable sits on my sturdy basement hardwood floor as in the picture above. The M3D's "reset" button was activated to quartz-lock at the standard pitch. Cartridge is the Denon DL-110 with the Emotiva XSP-1 preamp:



I also did the measurement with the Funk Achromat 1200 and did not see any difference (not unexpected of course since the mat itself should not be causing any platter rotational change unless there is slippage of the LP or mat over the platter).

As you can see from the lowpass-filtered green line, the overall speed is very accurate, hovering right around the 3150Hz test tone. Notice too that this doesn't look like the more chaotic "raw" graph from something like the less expensive "clone" Audio Technica AT-LP120-USB recently reviewed. You can also compare this with the Music Hall MMF-11.1 graph, and the Zorin Audio TP-S3 - way more expensive tables. And here's a supposedly "modestly" priced AVID Ingenium review with rather significant speed stability issues. (When look at these graphs, remember to mind the scale differences on the left, not just the shape of the raw tracings.)

If you have a subscription to Stereophile, the Analog Corner article in the May 2014 issue (p. 33) also has some numbers and graphs for the VPI Classic Direct Drive Signature, Continuum Caliburn, and the very smooth looking graph from the Onedof One Degree of Freedom (the review is also posted on-line.)

Here are the numerical results for my SL-1200M3D. (I paid a few bucks to get the DIN IEC 386 / IEC 45507 plug-in measurements as well for those interested.)


Lowpass-filtered, we see a nice +/-0.02% deviation. Over the course of ~60 seconds, it's good to see that the maximum deviation remained <+/-10Hz for the 3150Hz signal - good stability (Fremer's measurements are usually for ~30 seconds).

I try not to be a zealot over hardware - it's just a "thing" after all and can be replaced, but I do value objective "truth" as best I can show evidence of and am curious if I actually do experience something unexpected subjectively... So please don't take my comments as being some kind of "religious" cult-lover of the Technics SL-1200; I got it at a great price used, it has excellent build quality, and so far it sounds fantastic to me. That being said, here's something that Michael Fremer wrote in the May 2011 Stereophile in his Brinkmann Audio Bardo turntable review:
Virtually all electric motors "cog," ie, their rotational speed regularly fluctuates above and below the average speed as each magnet pole goes past each coil. A high-torque motor needs a greater number of poles—in some designs, dozens—and the more poles, the more cogging. With nothing to counteract the motor cogging that inevitably occurs directly within the platter of a high-torque, low-mass, direct-drive turntable, large amounts of wow and flutter are also inevitable.
Regulating a direct-drive motor's speed with a phase-locked loop produces tight speed control and measurably low levels of wow and flutter, but the motor's constant, ultra-high-speed hunting and pecking as it over- and undercompensates in the attempt to produce a consistent speed can create a jitter effect in the mid-treble to which the human ear is particularly sensitive, adding a hard, brittle texture to music. That describes the sound of Technics' now-discontinued SL-1200 series of direct-drive turntables, and explains why, despite their high build quality and relatively low price, few are used in serious audio systems, though some listeners claim that these 'tables can be modified to improve their sonic performance. 
Well, that sounds a bit scary doesn't it? But unless substantiated with some objective evidence, it remains just another scary theory among many promulgated by the "high end" (eg. the dreaded jitter, WAV vs. lossless compressed FLAC sounding different, digital cables, power cables, strange "room treatments", funky playback software, just to name a few). Surely something so ominous can be measured, right? Others have also voiced doubts about these claims; for example KAB doesn't seem to think this happens with the SL-1200.

So, I'm looking at the graph above and am wondering whether I'm seeing evidence of "ultra high-speed hunting and pecking". The frequency variation looks quite regular and clean. I assume we should be looking for significant random chaotic ups and downs in the graph that could be (supposedly) perceived as the "jitter" artefact. Sure, the Technics is not as good as the symmetrical, smooth and constrained undulation of the Onedof turntable (ahem, $150,000 folks). For less than $600 or so that I paid including the LED cue light replacement and aftermarket Funk Achromat, this 1970's Japanese designed performance seems pretty decent I think!

On a side note, if anyone dares to complain about jitter as a significant variable in digital playback, just look at how much 'jitter' is present with timing errors from vinyl! We're talking orders of magnitude compared to the usual picoseconds from typical decent CD players.

Ultimately, rotational speed accuracy and stability are just a couple of the variables in the complex vinyl playback chain; but important ones. Remember that the test LP itself will add its own variation and affect the results (eg. if the spindle hole is slightly off center, mild warping, etc. - the lowpass-filtering is supposed to compensate for this). I wouldn't therefore read too much into these measurements other than a guide to know when something is really abnormal. I agree with Fremer when he wrote in the VPI Classic Direct Drive Signature review:
The Onedof and Caliburn measure similarly, but their frequency graphs look very different. Are the sonic differences the result of differences in bearing smoothness, motor control, or both? At this point, I don't know.
Personally, at least I feel secure that my >10 year 'young' SL-1200 is holding its rotational speed well. A measured result of 3149.8Hz (3150Hz ideal) is essentially as good as it gets.

As for the supposedly audible complaints of "hard, brittle texture" in the earlier quote above charged at the SL-1200, I have no idea what he's talking about... Just because something uses quartz doesn't mean it's "hard and brittle" :-); just like silver cables = "fast" and "bright", right?

There have been debates about direct drive vs. belt drive vs. rim drive turntables over the decades but as far as I am aware, good controlled listening tests/comparisons are lacking so I think it's more important to focus on the actual execution of the turntable rather than lumping drive mechanisms in a simplistic fashion. I'm sure there are some terrible direct drive models just as there are terrible belt drive models.

For completeness, here are the Feickert PlatterSpeed test results at 45 rpm on my SL-1200 M3D over about 45 seconds (test signal target is 4252.5Hz):



As expected given what was seen at 33.3rpm. A bit more frequency deviation/fluctuation with the 35% higher rotation speed. Note that the +16.3Hz raw max frequency deviation is an anomaly due to that little spike at the end when I took the stylus off the record... Should only be +11Hz at most. Very good result I think!

Overall, I suspect the results here would be superior to many very expensive "boutique" turntables out there. I'll show some other measurements in the days ahead when I come across the opportunity.

Off to try out some zip-lining and white water rafting at Whistler this Labour Day long weekend. Enjoy the tunes everyone...

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Addendum: Here's another interesting thread and the original thread where the test was done on the idea of "cogging" with direct drive motors from a few years back. Clear as mud. Again, even if these results demonstrate imperfections in the drive mechanism, where's the evidence for perceptibility?

Friday, 22 August 2014

MUSINGS: "Pure, Perfect Sound - Forever"

Remember that much-maligned phrase "Perfect Sound Forever"? Of course you do! For the audiophiles out there who read the usual magazines, how can we not!? We only seem to be reminded of it every few months as it's trotted out like a nagging parent bringing out old transgressions - never forgiven, never forgotten.

The name of the person(s) who came up with that catch phrase has been lost in time; perhaps someone in the advertising back office at Philips... In full, it's actually "Pure, Perfect Sound - Forever" as prominently displayed in one of the earliest CDs from Philips (circa 1982):


This demo disk consisted of 14 tracks; combination of rock/pop (Elton John "Blue Eyes", Dire Straits "Once Upon A Time In The West"), with classical selections [see here]. Personally I have never seen a copy but can imagine that it would sound like the usual early pressings - a first pressing Billy Joel Piano Man perhaps (which incidentally needed de-emphasis processing to sound right [see list]).

As a marketing slogan, it has obviously worked. After decades, at least within the audio world, apparently people remember the "promise" of digital audio. I would of course agree that these early 1980s "first press" CDs were not the "ultimate" best sounding audio, but as I opined previously here (in reference to Pono and John Hamm's comments), just what is the best version of any album is a subjective judgement irrespective of whatever carrier medium... There have been many instances where I would easily prefer these old releases compared to modern dynamic compressed, distorted remasters (the inferior 2009 UMG Rolling Stones remaster of albums like Emotional Rescue from 1980 came to mind the other day as I was listening to it). The issue with the interpretation of this marketing phrase with many in the audiophile press and analogue evangelists when they malign "perfect sound forever" is that they're taking it to mean "best sounding version forever". Furthermore, some folks take this advertising slogan and heap upon it their own unfounded biases against digital as if the phrase somehow is evidence of an inherent "flaw" with digital audio! Remember, it has been 30 years since the introduction of the CD technology and we have yet to see credible evidence to demonstrate that well-digitized 16/44 isn't transparent beyond anecdotal opinions (just like there's no good evidence to demonstrate superiority of 24-bits or >44kHz sampling rates; assuming we're using a decent DAC playback system).

In the context of what I wrote previously with my adventures in analogue/vinyl, I believe that "pure, perfect sound - forever" as it relates to digital is more accurate than not. Let's look at the mains points.

Pure: I take it this refers to purity of the signal recorded free from extraneous distortion and noise. I don't think I need to say much about this since the digital format is indeed capable of encoding mathematically precise, "pure", even synthetic waves. Sine, square, triangle, sawtooth; whatever... It will be encoded on the CD within the resolution limits of digitization - precisely. Of course the analogue-to-digital converter plays a massive part in digitization quality but they're extremely capable these days. Noise and distortion technical limits of 16/44 are well understood of course. Vinyl in comparison as a physical object will have limitations in terms of noise and other distortion long before the mathematical precision of digital 16/44 data... This leads us to the second point...

Perfect: In reference to a digital sound storage system (ie. the CD and modern day digital files), one can say that perfect retention of the data and replication of the sound as encoded in the data is possible (or at least perfect enough for all practical purposes). It does get a bit boring measuring DACs these days because typical high quality DACs measure and sound very similar (atypical ones that employ vacuum tubes output stages or complex internal DSP operations for example, are a different matter!). I suspect it is this fact that leads various companies to shift attention to tiny differences like "jitter" to differentiate themselves or claim audible differences. In comparison, you can never say that any aspect of a vinyl system's music reproduction is "perfect". The mixing process for an LP requires compromises, the cutting itself could be imperfect, mass reproduction does not result in perfect copies (consider even the varying quality of the vinyl material used), packaging and shipping issues (abrasions, warped records anyone?), accidental scratches, dust and grime, imperfect turntable setup (VTA, VTF, azimuth, leveling, antiskating...), varying quality of cartridge/stylus/cantilever (tracking issues, inner groove distortion), phono pre-amp RIAA curves, etc.

Compared to the data integrity of a digital system, analogue just cannot match. The consistency of playback with digital would have had been revelatory back in the day; certainly a much more consistent quality of playback each time and sonic differences between good CD players are much smaller than that between different turntables and cartridges. As I wrote previously, I do believe analogue LP playback can sound fantastic and IMO there's no point rehashing the tired analogue vs. digital debate since there are so many factors influencing a good sounding recording and playback system. Yes, some LPs can sound better than some CDs and vice versa. Digital has fantastic sound quality if the original source isn't dynamically squashed to distraction, and vinyl has attached with it the pride of ownership unmatched by CD/SACD/DVD-A/Blu-Ray/files.

Forever: If anything, this is perhaps the least true comment about CDs. As an enduring object, the petroleum-based, non-biodegradable vinyl LP cannot be beat by digital as far as I am aware. It has been said that an LP can last 100's of years if stored properly. Easily spanning any of our lifetimes. On the other hand, there are instances of CD "rot" over time although personally I have many CDs hitting 20 years and they look good so far. Even 15-year old CD-Rs seem OK to me so far stored in a cool basement away from direct sunlight or inclement weather. Hard drives are more problematic and in the last 10 years of running my music server, I've probably had to replace each hard drive every 5 years on average with regular use. Solid state drives (SSD) are a bit of a mystery to me so far. I use them as boot drives rather than music storage due to cost and so far my oldest unit of about 5 years seems to be OK.

However, with digital, we do have the ability to make perfect copies each time so with some discipline around backing up (probably good to have 2 extra copies around stored at different physical locations), one should be fine for a lifetime. PCM is ubiquitous and the free FLAC file format I suspect will easily outlive any of us reading today... I wouldn't be nearly as confident about DSD file formats' longevity however (especially given how primitive they are).

"Perfect sound forever" as a description for the CD and digital audio in general has a 'ring' of truth to it. The key is to say it within a reasonable context and seeing it for what it was meant to be... A catchy ad slogan which did highlight the merits of digital audio. And it worked!

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In keeping with my recent interest / "re-acquaintance" with the vinyl format, here's an interesting article on the "rise" of vinyl. We'll see how this pans out in the years ahead. As I've checked out the vinyl stores locally, I notice that there's a nice mix of young and older folks looking around. I see about as much interest in the used vinyl as the used CD bins 'round here. There's a local large chain store that sells new LPs and I don't think there's large volume going thorough. Vinyl growth or not, I think it's fair to say that sales of a physical music product peaked at least a decade ago and it's not ever coming back for many reasons - convenience, storage, maybe environmental consciousness, the economy...

As imperfect as vinyl is, I'm having a blast rummaging through the bargain bins sorting through the oldies from the 70's and 80's constituting memorabilia from my "soundtrack of life" through the formative years :-). I've found many very clean, essentially mint albums over the months. To be able to buy it for "pennies on the dollar" makes it even sweeter!

One last thing. Needless to say, economically, there is one very important reason for music labels to "push" for a resurgence of vinyl. Anti-piracy. "Perfect sound forever" also means "perfectly copied forever". I sure hope we don't get a systemic situation where digital becomes maligned, crappy CD/digital downloads are released, and sonically decent versions are reserved for the LP release only at high prices. Doing so would sadly bias sonic quality towards the technically less accurate format.

Enjoy the music and the rest of summer (N. Hemisphere)!

Friday, 15 August 2014

AudioPhil's Corner: Viewpoint and Follow-up on the Dragonfly 1.2...


I was offered the opportunity by Archimago to share a few thoughts regarding the Dragonfly v1.2 which I graciously received as a pre-wedding gift from my good friend the Mago himself. However, before I go into that, I'd like to provide a little background on how I feel the entire subjective high end audio hobby has changed over the past two decades or so. This leads up to why I believe that the majority of consumer electronic products have mostly reached a technological performance plateau over the last few years and why I don’t think there are really any truly “bad” audiophile products out there any more in general.

First of all, I've followed the general evolution of the high end-audio scene off and on for the greater part of two decades and have shared insights with friends from both the subjectivist and objectivist camps; with members of both camps invited for hi-fi auditions on a few occasions which led to some very interesting dialogue ☺. [Ed: War!] As for myself, I feel that I’m currently straddling both sides, being able to recognize the merits (and flaws) of each. However, over time, I feel that there will be some kind of eventual reunification as the once elusive “high end” audio performance can now be obtained at far more attainable prices.

The one area in which all audio enthusiasts can unanimously agree to is that digital audio has improved significantly over the last 20 years, with the overall performance bar taking a quantum leap in the 90s, and then having that state-of-the-art performance trickle down gradually into much less costly products since the turn of the millennium. I still vividly remember being in complete awe with mouth agape when I first saw the Mark Levinson No. 30 and No 31 DAC and transport combo at a local high end store in the early '90s. That combo was insanely expensive, costing more than a new luxury car, and looked like it could have come off the captain’s quarters from Star Trek: The Next Generation’s USS Enterprise. It didn’t just sound incredible, it was the pinnacle of acoustics, aesthetics and literally cost-no-object build quality that made it widely regarded as the Holy Grail of digital high end audio for several years to come. It would have been my “preciousss” had I been able to afford it.
Mark Levinson No 30 Reference Digital Processor (Photo courtesy of Stereophile, Feb. 1992).
Although it cost a whopping $30K back then, it was so far superior to the quality of cheap mass market consumer electronic products at the time that if one could afford it, it might possibly be justified, like buying a Ferrari. Even today, the No. 30 and 31 are still sought after as icons of audio history.

Fast forward a few years and I was similarly awestruck when I saw my first HDTV feed on a 42” plasma display which at the time cost a cool $25K. Today a 42” LCD TV that is superior in every way would sell for closer to a hundredth of that price. Similarly, audio electronics have also advanced significantly in price-to-performance. Archimago not long ago measured my Oppo BDP-105 which had a measured performance that is off the charts, with noise and distortion levels that are significantly below the thresholds of human hearing acuity.

In fact, I believe that the “perceptible” (as opposed to measurable) performance of most consumer electronics products, which includes everything from digital cameras to flat screen displays to audio products have reached a plateau several years ago so the continued marketability of these products have primarily come from improving aesthetics and at the same time drastically reducing prices.

All these technological advances and marketing efforts are slowly but surely killing the subjective high-end audio industry. Once upon a time, there were mighty Mark Levinson products which were lusted for by many but attainable by only the most affluent and dedicated audiophiles. But today, something close to the “absolute sound” can be quite painlessly acquired by the masses, and it is that mass-market availability that has in no small way led to the decline and possibly the inevitable demise of high-end audio as we once knew it. An audio dealer will likely require significantly more persuasion to convince an ever shrinking base of hardcore and well-heeled audiophiles that a dCS Vivaldi digital playback system is worth $100K when one can buy an Oppo BDP-105 for a tad over $1K which also gets you one of the best Blu-Ray players available. That’s a pretty steep diminishing marginal return curve to climb no matter what your available resources. After all these years, the current reigning “preciousss” has in my opinion lost much of the sizzle in the ”s”. My MacBook Air is technologically advanced and also beautifully sculpted from curved shiny aluminum yet doesn’t have to cost six figures...

Stepping back to the subjective camp for a moment, I will make mention that Archimago stated that he feels that the Dragonfly gives an overall “warmer”, more pleasant and less hard-etched sound than the AudioEngine D3 despite a bit inferior measured performance. I think that’s yet another example of the paradox that fuels the never-ending debate between the subjective and objective camps. If the original audiophile goal should be to seek the most accurate reproduced sound possible, why do subjectivists (or even normal human beings without the “golden ears”) seem to often prefer euphonic distortions in the form of tubes, vinyl, etc.? However if the ultimate goal is to simply enjoy the music, then should we even care?

Finally, I will say a few words on my overall impression of the Dragonfly, but really, there is nothing much more that need to be said that hasn’t already been covered by many others before. It is well made and feels like a very solid and weighted USB stick. I never had the chance to do an intensive A/B test with it but the Dragonfly does a fine job of radically improving the headphone output from my MacBook Air which is most obvious when listening to AKG K-702 headphones, even though it is still a very noticeable improvement even with cheap earbuds. The soundstage is much larger, with instruments having far better stereo imaging and voices had more body and depth. The Dragonfly was able to extract significantly more micro-details, especially on live recordings so it is able to more convincingly put you at the recording venue when compared to listening straight off a MacBook Air or iPhone. The bass is full but not bloated. Overall, the sound is detailed yet well balanced and smooth. There was minimal listening fatiguing even after a couple of hours of critical listening, and I was able to listen at louder than normal levels.

Overall, this nifty $150 DAC offers exceptional price-to-performance much like a $500 DLSR or LED TV, or the latest Android smartphone or many other techno gizmo these days. Heck, it may even sound as good as the revered ML No 30 DAC (in a DBT, of course) if plugged into my main system. Near state-of-the-art performance in consumer electronics products has never been better or more attainable.

Happy listening!

Thursday, 7 August 2014

MEASUREMENTS: AudioQuest Dragonfly v1.2 Reviewed

An audiophile buddy of mine (AudioPhil) got married a few months back and a few of us decided to chip in to give him one of these Dragonfly DACs for being a good sport :-).

I don't think the Dragonfly requires much introduction since it has been around in the 1.0 iteration since 2012 and Stereophile had it grace their cover page with a full review back in September 2012. It uses an unspecified ESS Sabre DAC (not sure if confirmed, likely the ES9023 with integrated 2Vrms driver - there's also the older ES9022 chip) and the USB communication part is the TI TAS1020 performing asynchronous data transfer. I haven't read anywhere if these parts have changed in the 1.2 version. Supposedly, the new version has improved sonics ("Even smoother and more open sound!" seems to be the official tagline).


It looks good and feels great in the hand with a slight rubberised texture to the surface of what seems to be a metal shell underneath. As you can see above, it is slightly smaller than my AudioEngine D3 previously tested. Despite the smaller size, the weight on the Dragonfly feels heavier; hence a noticeable ruggedness and density to the package. It comes with a small black pouch for safe keeping along with the USB cap. I don't think the Dragonfly comes with a 1/4"-to-3.5mm adapter cable like the D3.

You can see the Dragonfly indicator change color depending on sample rate. AKG Q701 connected.
In use, I found that it didn't get too warm and was clearly cooler to the touch after about an hour of listening compared to the D3. AudioEngine was quite open about revealing the use of the LME49726 op-amp for the headphone output and presumably the Dragonfly utilizes the integrated op-amp function of the ES9023 (or similar chip) as per the "direct-coupled circuitry" in their promo material. From a price perspective, both the AudioEngine D3 and Dragonfly are priced similarly, $150CAD for the Dragonfly and $170CAD for the AudioEngine D3.

Other specs like output impedance (12 ohms Dragonfly, 10 ohms D3) and power (150mW Dragonfly, 200mW D3), both being driverless USB Audio 1.1 devices with a maximum of 24/96 sample rate (it is capable of the important 88kHz for DSD conversions) further adds to the functional similarities between the D3 and Dragonfly. These driverless USB DACs make it really easy to just "plug 'n play" with Windows and Mac OS X - I did not try using Linux but that should not be a problem.

I. Objective Evaluation

A. The Basics
As you may recall, at 100% volume, the AudioEngine D3 would clip. This was noted to happen with the Dragonfly v1.0 as well; discussed in the Stereophile measurements, and used to show some atrocious distortion numbers by Light Harmonic when they did their "Geek Out vs. the Others, 3rd Installment" (5% THD+N!? Sorry, that's just plain nasty and paints the situation in a much poorer light than it should even though objectively correct...). Well, it looks like this issue has been resolved with v1.2; here's the oscilloscope measurement from the unit I have on hand:
Square wave at 0dBFS.
Sine wave at 0dBFS. No clipping at 100% volume.
Peak volume of 2.63V correlates with an RMS voltage of 1.86V. Hmmm... I suspect this must be what they did to avoid clipping if the ESS chip used is the ES9023 with 2Vrms capability; dropped the highest volume level settings (notice that the Geek Out test posted was with 100% volume at 2Vrms).

There is bit of channel imbalance in the graphs above... It represents approximately a 0.5dB difference (left channel louder) at full 100% volume.

Impulse response is the typical symmetrical appearance of a linear phase oversampling filter. The signal maintains absolute polarity. No surprise.

B. RightMark 6.4.0
Okay, with the above done, let's have a look at the resolution of this DAC using the RightMark test bench. Like with the AudioEngine D3 tests, this was performed with the latest free version using the ASIO device interface.

Setup:

Test machine + AudioQuest Dragonfly --> shielded phono-to-RCA cable --> E-MU 0404USB --> shielded USB --> Win 7 laptop running RightMark 6.4.0

Summary of the machines tested (the laptops were described here in more detail although OS has been updated):

1. ASUS Taichi 21 Ultrabook (early 2013): Intel "Ivy Bridge" i5-3317U (1.7GHz dual), 4GB, Windows 8.1 x64, 128GB mSATA SSD, USB3 port, foobar + WASAPI component 

2. Apple MacBook Pro, 15" (mid 2009): Intel Core 2 Duo (2.26GHz dual), 8GB, OS X 10.9.2 "Mavericks", USB2 port, WD 640GB SATA HD, Decibel player (AIFF files)

As you may recall when I tested the AudioEngine D3, I measured that device with 6 different machines! It was clear that this made no difference to the measured audio output (and I heard no difference either - indeed folks, bit-perfect does mean something)... For these tests, I just chose a PC platform and a Mac platform, both are laptops, but with major differences like OS, file types (FLAC vs. AIFF), different generation Intel CPU, different player software, USB2 (Mac) and USB3 (PC).

Let's start with the 16/44 standard resolution (CD-quality) signal:

The 2 columns on the left are the measurements from the Dragonfly 1.2 - leftmost using the ASUS Taichi laptop, second one using the MacBook Pro. The middle column is the result from the AudioEngine D3 connected to the ASUS Taichi (exact same cables and setup as the leftmost column measured the same day), and the last two on the right are with my higher end DACs - the Transporter using XLR connection, and the TEAC UD-501 with XLR output measured awhile back. Note that because the AudioEngine D3 clips at 100% volume, the measurements were done at 91% which approximated the same maximum output voltage as the Dragonfly.

As you can see, when it comes to noise level and dynamic range, all these DACs are capable of ideal 16-bit resolution. Very low noise floors all around. Where things do seem to separate out is in the area of distortion - the Dragonfly appears higher in this respect compared to the others (repeated this a number of times to double check). Also, the stereo crosstalk is objectively higher with the Dragonfly. Here are a few of the graphs off RightMark:
Frequency Response - Transporter seems to roll off a wee bit more.

Noise floor.

Dynamic Range test.

IMD+N

Stereo crosstalk - note the significant difference between the Dragonfly vs. the others.
Now, let us look at the 24/96 (high-resolution) results:

The columns are arranged the same as above. Leftmost two columns represent the Dragonfly results, then AudioEngine D3, then the Transporter (XLR), and finally TEAC UD-501 (XLR).

Again, no difference in results between using the ASUS Taichi and MacBook Pro laptops despite disparate hardware and OS. The Dragonfly is indeed capable of >16-bit dynamic range, and at approximately 106dB, that's about 17.5-bits (same as what Stereophile found with their v1.0 review). As with 16/44 above, however, when you look at the measurements of distortion, the AudioEngine D3 is capable of less distortion and dynamic range is about 0.5-bits higher. Needless to say, the stand-alone "higher end" DACs like the Transporter and TEAC UD-501 with XLR outputs handily beat these little USB DACs by about another 'bit' of dynamic range and lower noise floor (especially the old Transporter!) measurable within the limits of my ADC set-up of course.

Frequency Response (no significant difference <20kHz)
Noise level - notice Dragonfly slightly higher especially in the bass.
IMD+N
Stereo Crosstalk - Dragonfly again significantly higher crosstalk... Very impressed by the Transporter using XLR cables! 
C. Jitter
As usual, I'll use the Dunn J-Test paradigm. Easy enough to do...


As in previous tests, with these asynchronous USB DACs, the Dunn J-Test spectrum generally looks fine. This is the situation here, no evidence of jitter issue at all using this simple measurement... Only very slight noise floor differences between the two laptop machines.

II. Subjective Evaluation

So I asked my buddy AudioPhil (the guy who actually owns this Dragonfly) to provide his subjective review and it looks like he'll be providing a little write-up of his own in the next while... While that's in "gestation", I figure I'll jot down a few of my subjective impressions and comparisons on this little device.

I spent about 2 weeks listening to music with this DAC/amp (some before, and some after the objective testing) and comparing what I heard with the same tunes off the AudioEngine D3 and ASUS Xonar Essence One (which remains my primary DAC on the computer workstation). Each of the devices have quite different DAC architectures; Dragonfly with the ESS Sabre, D3 with an Asahi Kasei AK4396, and the larger Essence One using TI/Burr Brown PCM1795s (quite unfair comparison given that it's not a simple USB bus powered device!). It's impossible to "instantaneously" switch headphones / DACs and then level-match compare... I tried my best.

A potpourri of DACs and headphones: AudioEngine D3, AudioQuest Dragonfly 1.2, ASUS Xonar Essence One; Sennheiser HD800, AKG Q701, Etymotic ER-4B IEM.
The published output impedances for the Dragonfly and D3 are around 10-ohms - the Essence One apparently has similar output impedance as noted by 'Xnoreq' in the comments although there are estimate of it being in the single digits [I'll need to have a look at this later]. So, to give them all a fair chance, I'll speak about what I heard using the Sennheiser HD800 (300-ohm input impedance) headphones primarily. Thankfully the HD800s have high enough sensitivity (102dB at 1Vrms) so music could be played reasonably loudly with the Dragonfly and D3 even with the lower power ratings. Of course from a price point perspective, the HD800 isn't the kind of headphone one would expect to see mated to an inexpensive USB DAC like this!

I started with listening to some "vocal audiophile jazz" - Diana Krall's The Look Of Love (2003 24/96 DVD-A) being one of my favourites over the years and particularly "Let's Fall In Love" as a track I've been using to compare new gear with since around 2000. I like the instrumental portion in the middle of the track and particularly the detailed resolution of the bass and piano through that portion. With the Dragonfly, the piano sounded rich and full. The bass was detailed with each pluck easily discerned. In comparison to the D3, the Dragonfly sounds more laid back and "smoother". The D3 just seemed to have a bit more sparkle, slightly brighter; for example the high-hats on the song stood out a bit more from the rest of the instruments. Personally, with my "Anaxilus mod" Sennheiser HD800, I preferred the D3 rendition but I can imagine with even brighter headphones, the Dragonfly may be preferred.

While staying with the vocal genre, I listened to some Nat King Cole - Cole EspaƱol (HDTracks 24/96 release, and no, I don't actually believe this album has enough resolution to warrant the high-resolution format). On a track like "Quizas, Quizas, Quizas", the Dragonfly was a joy to listen to with the HD800! This old 1958 recording can be a bit "brittle" through many DACs and the Dragonfly just made the instruments sound less harsh and the voice "ultra-smooth". I found the same on some traditional Chinese erhu recordings where the pleasant demeanor of the Dragonfly helped impart an enjoyable, smoother experience.

Time for some heavier fare - how about AC/DC Back In Black (1988 DR12 CD)? Pump this baby up to rock! The intro to track 1 - "Hells Bells" - with those church (er... hell's?) bells sounded realistic in terms of the attack and smooth decay using the Dragonfly. While not exactly the paragon of audiophile recording technique, this analogue recording from 1980 is about as "hard" as I like my rock to be and the Dragonfly was able to render it nicely. However, I found the Dragonfly to be a bit more on the "polite" side of things as compared to the more aggressive sound of the D3 which I thought fits this type of music better.

I listened to a number of other genres to get a feel for things - Pet Shop Boys Actually (2001 remaster), Yello Touch Yello (2009), Eiji Oue & Minnesota Orchestra Stravinsky: Song Of The Nightingale, Firebird, Rite Of Spring (1996 Reference Recordings), Ed Sheeran x (2014). In general, I thought that the Dragonfly performed well but was more at home with an acoustic set than say the synthpop or electric guitar rock. Despite the dynamic range compression especially near the end of the song, a track such as Ed Sheeran's "I See Fire" with overlaid vocals and relatively simple instrumentation found on x sounded just fantastic through the HD800 with the Dragonfly; bass response on that track was simply cavernous in depth.

Not unexpectedly, the much larger (and unportable) ASUS Xonar Essence One sounded better than the USB stick DACs. This has more to do with the quality of the headphone amp than the actual DAC function I believe - providing a more full-bodied, powerful sound overall (even more cavernous bass at the end on "I See Fire"!).

Near the end of my subjective evaluation, I put on some mono music to see if I could easily detect the channel imbalance noted above. For this I used the mono Beatles remasters from 2009. I listened to most of the Revolver and Sgt. Pepper's Lonely Hearts Club Band albums one evening. On the whole the stereo imbalance at normal listening levels with the Etymotic ER-4B balanced armature IEM (100-ohm impedance, excellent noise isolation) was subtle when I compared it with the output from the D3. I was concerned about perceptual bias knowing the objective results earlier so I asked my wife and she identified correctly the slightly louder left channel after listening for a bit. So, we're looking at a small, but perceptible imbalance.

III. Summary / Conclusions

There you go, the objective and subjective evaluation of the AudioQuest Dragonfly v1.2. Overall, from an objective perspective, it doesn't measure as well as the AudioEngine D3. The Dragonfly's 24-bit dynamic range is lower by about 0.5-bits in comparison, plus harmonic and intermodulation distortions measure higher. Furthermore, there's a bit more stereo crosstalk with the Dragonfly. Realize of course we're looking at tiny differences in terms of real-world audibility. For example, what audible difference is there between 0.011% THD (Dragonfly) versus 0.0009% (D3)? Would our headphones/speakers be able to manage such low level of distortion or our ears capable of such resolution? Remember that a typical NOS DAC like the old TDA1543 measures 5-10 times higher in terms of THD and IMD yet they can still sound OK (and in fact some audiophiles swear by them). The other difference was increased stereo crosstalk with the Dragonfly measured around -72dB. Compared to the others around -90dB or less, this sounds like a lot. Again, remember that a typical LP cartridge has "only" about 25-40dB channel separation at 1kHz. Therefore, again it's unlikely you're going to notice an audible problem.

The one area of concern for me was the channel imbalance on objective testing at 0dBFS on the oscilloscope with this unit. Even so, it was difficult to detect a difference at normal listening levels through my Sennheiser HD800 and AKG Q701 playing stereo music but could be detected with mono recordings using the Etymotic ER-4B IEM. This could really be a problem if one's headphones also had a slightly louder left channel imbalance issue. Perhaps others can double check if this imbalance is present with their own Dragonfly units.

I cannot help but suspect that the advertised "direct-coupled circuitry" where the op-amp is integrated into the ESS Sabre chip might be the reason for the relatively poorer objective test results. Compact size is achieved with this kind of arrangement but physical factors like significantly higher heat production could I suspect limit absolute sound quality from the DAC chip itself. I don't know if AudioQuest could have also "tweaked" the settings for the DAC chip to bias towards a more pleasant sound.

Here's the bottom line... If you're looking at the AudioEngine D3 versus Dragonfly v1.2 and want the best objectively accurate sound quality, go for the AudioEngine D3. It measures and sounds like a much more expensive separate DAC on a stick! However, the main caveat is that it clips at 100%, so keep it around a maximum of 92% and you'll hear some really clean audio. Remember what I also said previously about allowing a portable device to clip - it may not be an unreasonable trade-off when you just need that extra bit of volume in a noisy environment where a little distortion is fine. The D3 is also a little bit more expensive around here currently (only talking about $20 difference).

On the other hand, the Dragonfly is built very well and I would rate the look and feel of the unit higher than the D3. The color-changing dragonfly indicator based on sample rate is also a nice touch. Furthermore, it is slightly smaller and significantly cooler to the touch than the D3 after an hour of music being pumped through. Output impedance isn't much different between the two (both around 10-12 ohms), so check if you have higher impedance headphones (80+ohms) for best performance. The D3 can play a bit louder but remember this is with the potential for clipping at 100% volume. My usual benchmark for a "good enough" headphone amp is one where I would not need to put the volume to 100% to enjoy my AKG Q701s... And the Dragonfly is clearly good enough in this respect for what I listen to.

The main criticism I have of the Dragonfly is that ~0.5dB channel imbalance I found which I hope is just variability among samples rather than a systemic finding (remember that even well regarded cartridges for vinyl playback can have stated channel variances up to 2dB). Subjectively I thought the Dragonfly imparted a "pleasantness" to the presentation rather than aim for absolute technical precision as demonstrated objectively. Compared to the typical headphone jack on a laptop, it'll provide your headphones with more power, lower noise floor, and more dynamic range especially for 24-bit audio. I'd be very curious to know what objective differences there are between a 1.0 and 1.2 version of the Dragonfly if AudioQuest claims that 1.2 sounds better (other than no clipping at 100% volume)...

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Happy listening everyone... Considering the 24-bit performance from the AudioEngine D3 and Dragonfly, consumer audio technology is clearly getting better, smaller, and more affordable!

Weather has been very nice here in Vancouver lately. Off to an Alaska cruise next week so hopefully there will be blue skies and maybe see a few whales along the way. Catch you all later...

Friday, 25 July 2014

MUSINGS: Vinyl Update - Technics SL-1200 M3D

This week, I thought I'd put up an update on the analogue/vinyl changes I've made in the last few months since the "Vinyl Time" post back in May.

The Sony PS-T15 was pretty good. It sounds reasonably quiet but certainly not of "heavy build" quality weighing in at 5kg and things like the fluidity of the tone arm and resistance to vibration left a bit to be desired. I started buying a few more LPs and eventually decided it was time for a little upgrade to something a bit more substantial...

Looking around Craigslist, I was able to snatch up a lightly used Technics SL-1200 M3D turntable for a pretty good deal (<$400CAD). Based on the serial number, it looks to be made in 2002. The metal body and tonearm were immaculate but there were a couple small defects; a small imperfection at the base of the platter which doesn't affect the actual record surface or motion and a pop-up light which burned out. The platter looks really good with no scratches or anything other than that small imperfection (looks like a 0.25cm dent at the lower edge) so there was no reason to change it. I replaced the pop-up incandescent light with an LED (a shame that Technics didn't make it easier to replace the original incandescent bulb since it seems to burn out quite commonly). It came with a Stanton 890SA MM cartridge which supposedly could sound good with a new stylus/cantilever (maybe I'll check this out in time).

As you probably are aware, the Technics SL-1200 line consists of a series of turntables originating back in 1972. They were in production all the way to 2010 when discontinued. The motor is a high-torque magnetic direct drive and quartz-locked by 1979 with the introduction of the SL-1200 MK2. It starts and stops in <1 second. The specs look good with rumble at -78dB (DIN-B, check out the gory details) and 0.025% (JIS) wow and flutter... These numbers easily give many much more expensive "audiophile" turntables a run for their money (interesting opinion). Some have said the tonearm is the weakest link in the Technics line and replacements can be found (many aftermarket mod like this from KAB or this article with SME tonearm attached). I haven't played with many tonearms but it's certainly nice to have easy VTA adjustment with this stock design. Like almost everything else in this world, opinions vary and there are the detractors as well like this guy who seems to have a problem with direct drive tables in general, and Michael Fremer's assertions.

Finally, at 12.5kg, this unit is on the heavier side of things (not ridiculously heavy of course). It's built like the proverbial tank and I suspect will easily last me a lifetime assuming the electronics don't break down or some physical mishap. Build quality is fantastic with a metal base and rubberized undersurface for vibration reduction. Legs are functional and height-adjustable for leveling.

Here's a look at the innards exposed when I replaced the pop-up light:

Since the M3D model was meant for DJ use, it doesn't have a hinged cover and instead the lid is just the standard SL-1200 lid loosely placed on top... I got a DeckSaver lid instead which fits quite snug and overall I think it looks pretty good while keeping the dust away (I heard they're discontinuing this product):

One final "upgrade" is the Funk Achromat 1200 replacement mat instead of the standard rubber Technics mat. Some Vaseline/petroleum jelly underneath to "bond" with the platter supposedly helps. Here she is juiced up and ready to spin:

I've got a Shure M97xE cartridge in place now on this 'table and have a Denon DL-110 on order... Looking forward to hearing the difference the cartridges make.


A look now at the front end with a some of the albums collected (about 1/2 of recent purchases) over the last few months:

As you can see, other than the Daft Punk Random Access Memories on the left edge, the rest of the albums are old-skool or "audiophile approved" 70's (Steely Dans, Dark Side...). I grew up in the 80's and other than some albums my dad had, I never bothered to collect any of the vinyl from back in the day myself... Until now :-). Already, a few of the albums by then were sourced from digital. I have Dire Straits' Brothers In Arms (isn't it amazing how many remasters there are of an album that was essentially 16/44? DVD-A, SACD, 20th Anniversary, recently 2013 MFSL!), and Madonna's True Blue which is speculated to have been an analogue recording but digitally mixed (ADD SPARS code?). Madonna is just to the left of Peter Gabriel's So which itself was produced with digital gear and effects. And so it goes...

Knowing myself (I think!), I doubt I'll ever be a rabid vinyl fanboy... As a result, I don't think I'll end up being any kind of "completist" collector. Certainly right now, I don't have much interest in the new digitally remastered LPs although I have a few already and they do sound great (Dark Side, Graceland, Kind Of Blue).

So... How does it sound overall? Really good.

Noticeably more authoritative bass and lower noise floor than the Sony PS-T15 previously (using the same Shure M97xE cartridge). Albums like Steely Dan's Aja sounded punchy and clear as it should. Good quality new albums like Miles Davis' Kind Of Blue (Columbia 180g remaster release) sounded sweet, palpable with a nice soundstage. On good vinyl, the surface noise was almost imperceptable (unless the volume was turned up excessively of course). Remember thought that I have a very quiet basement sound room so almost any imperfection is quite easy to hear - I had to change my HTPC power supply to a fanless design because I could hear it in that room despite it being a "quiet" design. The aforementioned Kind Of Blue of course has quite high tape noise which was easily audible above the turntable / cartridge noise floor. Michael Jackson's Thriller sounded realistic with the creaking doors, zombie noises, and of course Vincent Price's inimitable sinister dialogue and laugh.

It's difficult to do a proper comparison, and I found it hard to notice a difference between the Achromat vs. rubber stock Technics mat. The Achromat does look nice on the platter nonetheless.

In the next few months I'll take some time to evaluate how some of my albums sound in both CD and vinyl formats and see if I have a preference overall. It's quite clear that the sound is different and how one decides which version is preferred has more to do with factors other than just resolution which in theory (and in my experience so far), digital will win without question. There's no doubt that vinyl has more distortion. Physical factors like slight vinyl warping and cartridge alignment geometry affect the sound, not to mention the fact that the inner grooves cannot maintain the same quality as the outer grooves (ie. inner groove distortion - a 24-minute monologue). I'm sure everyone also has at some time heard the pops (thankfully not common, usually associated with damaged used LPs), lower level crackles (a bit more common unfortunately, likely due to poorer quality vinyl material or damage from previous owner's gear), and low level surface noise (there's always some mechanical friction, essentially universal if you pushed up the volume during playback). Depending on the music, I can generally handle the excess noise; for example, pop and rock recordings will mask out much of the softer distortions but if I'm listening to classical, I find even the low amplitude noise will mar my listening enjoyment. It's no wonder that the classical community generally embraces digital. Of course resolution isn't the only determinant to whether a recording sounds good, so even though reason and science tells us that for the same original signal, a good digital system can offer better fidelity, we're generally not presented with that same original signal being stamped on to the vinyl. Remember, to compensate for the limitations of the LP medium, the mixing and mastering has to be different. And I wonder if often compensating for these limitations could result in an overall more pleasing sonic product. I can certainly appreciate what vinyl aficionados have said for awhile; when the stars align with good vinyl, it does sound heavenly... The problem is that they don't always align :-(.

As I'm putting the finishing touches to this post, look what showed up:

The Denon DL-110 high-output moving coil cartridge ("HOMC"). Nice package with an overhang gauge, built-in "magnifying glass" (round part under the cartridge), stylus brush (in white plastic packet), and a metal weight balance plate (cartridge weight is only 4.8g). With a 1.6mV output, it should have no problem mated to any phono preamp (no need to add step-up moving-coil amplification). Frequency response should be flatter across the audible spectrum (especially the highs) and let's see if the sonic resolution picks up significantly with this baby compared to the Shure :-)...

I'll be away a bit through the summer. Enjoy the (hopefully good) summer weather for all in the Northern Hemisphere! Happy listening...

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BTW: A few months ago I mentioned I ordered the Light Harmonic Geek Out 720mW DAC. Well, I waited for >2 months on the pre-order line and decided to cancel... It would have been fun to run it through some of my own measurements. Since I don't really have very low efficiency headphones needing the power, there just wasn't a need and likely the DAC would be sitting unused. I rolled the $$$ into the toys above instead - which will definitely get more use!

August 3, 2014 Update: A cool Technics ad circa early 1970's when objective measurements were more important for selling gear rather than just word-of-mouth subjective reviewers :-).

(Found here.)

Thursday, 17 July 2014

MUSINGS: The Distortion of Truth... More obfuscation.

Guys, check out this video from Harman:


Check out the segments from 11:30. LOL. Somebody has to go back to school and learn the difference between data compression (ie. MP3) and volume compression (ie. crappy engineer) as demonstrated by those waveforms. On the one hand they say they want to sell "better" sounding recordings but they're obviously going after the scapegoat (MP3) instead of the real culprit - themselves. The ones who allowed their recordings to sound like crap. The ones who apparently never listen to their own recordings or allow their own engineers to volume compress to death in the "loudness war"... Geez... Hans Zimmer talking about "filling your soul" when his own Dark Knight Rises from 2012 has a DR of 7 for an orchestral soundtrack on CD and 24/48 HDTracks! Do you think that MP3 was to blame for that, Hans? Shameful.

What a joke. "Head bob test?" Four times more bobbing with higher resolution audio?!

Here's the final comment:

Folks, we have a problem here. Just who is the audience they're targeting? Why would Harman produce this video - they want to sell more CD players or something? I've seen some comments about this leading into their DSP Clari-Fi system which sounds like a fake surround algorithm to me - I want the real volume uncompressed audio, not a DSP reconstitution, thank you (here's another opinion). But with a general comment as in the screen capture, they seem to have a problem with downloads (presumably all downloads including lossless), and they have a problem with streaming (presumably all streaming no matter the bitrate and maybe including lossless). To obfuscate the term "compression" as both volume compression (poor DR) as well as data compression (MP3) totally damages credibility here and understandably would frustrate if not insult any reasonably knowledgeable music lover / audiophile (especially ones who have tried blind testing high bitrate MP3!).

In sum: "Please consumers. Audio files and streaming suck. Listen to albums start to finish because artists put a lot of work into sounding good. Buy physical." Somewhere in there is the allegation that the physical (LP, CD) sounds better with no real evidence (oh yeah... that non-scientific head bobbing observation). A desperate plea to increase physical sales?

Yeah... Good luck with that. What a mess of a "documentary".

Monday, 14 July 2014

HOWTO: Spotify (Free) Streaming To Squeezeboxes



It's been a great weekend!

Managed to enjoy BBQ with some family visiting overseas for summer, enjoyed the World Cup finals (congrats Germany), finally put up the dining room pendant light (waiting months for the thing to come in stock!), finished some work-related financial paperwork, and finalized some scheduling for a trip to China later this year. Not bad for a weekend.

Even better for this weekend... I rejoiced at the arrival of Spotify to Canada. Previous to this, I was accessing it through Hola! Unblocker on occasion to have a look at what all the Americans have been enjoying. I guess one of the conditions to Canadian entry must have been to include Canadian content and perhaps French language content - French ads show up once awhile now. I might get a subscription in the months ahead depending on how often I access it on my cell phone and around here at home. The fact is, I already have a large collection of music on my server and the music collection is growing as I add more vinyl titles (in that regard, I've made a number of changes in the system which I'll post about later).

This brings me to thinking about these streaming services which I'll also talk about in the days ahead. For now, I'll have a good listen to Spotify and see how it integrates into my life.

Since I have a full Squeezebox "family" around the house, I figured it would be nice 'tuning' into the Spotify stream with the devices. For those interested in trying to stream free Spotify (with ads) to their Squeezebox system, you can follow the instructions below originally found in an older Squeezebox Forum post (thread started by 'ejnj' in 2011 but instructions from Nick Kewney). Remember that the Squeezebox Spotify plug-ins require the 'Premium' account. This 'hack' essentially converts the audio from your PC to a stream for the Squeezebox device through the PC's URL (making the PC audio output a radio stream); music selection is through the Windows PC's usual Spotify app. I've included the instructions here with some annotation for my Windows Server 2012 R2 system:

Playing Spotify Free (with ads) through Squeezebox

Spotify is a peer-to-peer music streaming allowing users to listen to specific tracks or albums on-demand.

Despite launching clients for Android, Symbian and iPhone OS, an officially supported Squeezebox Server (formerely SqueezeCentre) client for Spotify hasn’t yet been unveiled (there's both an official plug-in for Radio and Touch now as well as third party Triode plug-in for the older units). Until somebody gets their Perl boots on and creates one, I’ve created a short tutorial demonstrating how to stream audio from Spotify on your PC to your Squeezeboxes. It works by utilising DirectSound Bridge, a small wrapper which exposes the playing stream as an MP3, which can be received by your Squeezebox.

It really is pretty simple. To start, you’ll need to download two files to your PC:

* The Lame MP3 Encoder (I've included the link to RareWares - I used the 3.99.5 "for older Win32 OS's"; the 64-bit version did not work for me) 
* DirectSound Bridge (current "dsbridge-20090727-bin.zip" worked for me)

Next, you'll need to:

1. Close the Spotify application if it is currently running. On Windows 7, you might have to launch the Task Manager and end the process. (Best to go up to File/Exit on the Spotify desktop app to shut it down.)

2. Open the Lame MP3 Encoder archive you just downloaded and locate the file “lame_enc.dll” and copy it to the Spotify directory on your local PC (e.g. C:\Program Files\Spotify). On my Windows Server 2012 R2, as Administrator, use: C:\Users\Administrator\AppData\Roaming\Spotify.

3. Open the DSBridge archive and copy “DSound.dll” and “DSBridge.ini” to the same folder in step 2.

Open Spotify as normal and start a track playing. It’s best you turn the volume down as your PC will only be used as a controller for streaming to your Squeezeboxes. You will notice a new icon in your system tray. It’ll be blue when idle and green when streaming music (the icon looks like a colored orb; put your mouse pointer over it and it's tell you which port - usually 8124).

You’re done. Now, you just need to tune in to your stream from your Squeeze Centre web control panel, in effect creating the bridge between Squeeze Centre and Spotify.

Do this by entering your Squeeze Centre address into the address bar (mine is http://192.168.1.80:9000).

Locate Internet Radio / Tune In URL on the web interface and enter the address of the PC running Spotify. In my case it was http://192.168.1.80:8124.

In a few seconds, you should hear your Squeezebox connecting to the server and playing your Spotify stream. You'll hear that the music from the desktop speaker will cease when the Squeezebox plays. Track titles and artist will be displayed, no album cover image. 

Tip: If you don’t know the address, go to your PC and press WINDOWS+R, type CMD and enter which will display a command prompt window. Now enter ipconfig and press enter again. The IP address will be displayed.

Of course by doing this, you'll need to use the desktop app to search and play your playlists. Not too bad if I'm on a computer and can Remote Desktop into the server machine. Note that this process will recompress the incoming Spotify stream (I believe Ogg Vorbis 160kbps VBR for the free content) to an MP3 320kbps - don't be afraid, it still sounds great! Tuning multiple Squeezeboxes to the same URL didn't work for me resulting in me needing to restart the Spotify app to get music out again.

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I hope the instructions above are clear for those giving it a try.

Have a great summer! Enjoy the music... Cuz theres's a lot out there!