Review: dB Audio Labs Tranquility USB DAC Signature Edition

I was skeptical on whether it's clever viral marketing or genuine raves from early adopters, but dB Audio Labs' Tranquility got my attention.  I was scouting Audiocircle and Audiogon forums and there were threads on the DAC with words describing it as "the best USB DAC money can buy", "Can't believe it's not analog", etc.  That keyword "Analog"  has always been the holy grail for most of us, so I felt I got to try it out.  dB Audio Labs also makes a non-signature version of the DAC ($1,495 vs SE's 2,395) , and two USB cables ($295 and SE's $395, $100 less when purchased with DAC).  There's a 30-day return policy and a limited-time $500 off current retail prices, so I ordered the signature version of the both the DAC and the cable.


Design and Technology
The Tranquility replaced my Bel Canto DAC 2.5 in my desktop system.  The Tranquility is a simple looking (sort of..DIY) silver aluminum box with only one USB input and one pair of high quality RCA outputs.  So simple that it does not come with an operating manual (dB Audio Labs has excellent support, and the guys there will guide you personally with any set up questions you may have).  There is an IEC power connector and voltage is set from factory either for 110v or 220v.  There is a switch internally to let you select a different voltage in case you want to use it in your holiday villa in Europe or Asia.  dB Audio Labs does not give detail of the DAC's components nor specifications.  Eric Hider, the proprietor, says that he wants potential customers to listen with their ears, rather than imagining what the DAC would sound like from reading its specs.  Fair enough.  However, we do know some features and design concept of this DAC from Eric's collection of posts from the afore-mentioned forums.  

The DAC chip set itself is 16-bit, and is set to run in non over-sampling mode (see earlier blog - The Rise of NOS).  The mystery chip is either a new old stock Philips TDA1541, TDA1543 or a Burr-Brown PCM56.  It accepts 44.1kHz to 48kHz sample rate.  Any input above 16-bit, or 48kHz is flagged by the USB implementation and correctly down-sampled by the computer, so you can still listen to your collection of hi-resolution music files, but at lower bit and sampling rate.  Non-PCM digital data (DTS or Dolby encoded) will just not play.  There are posts by people stating that the Tranquility does not use any digital filters but I believe it utilizes an analog low-pass filer (the box is small, and no way they could use a transformer output device to also act as a low pass filter a-la Audio Note).  Eric told me the output impedance is around 600 ohm and the output voltage are "hotter" than normal DACs (usually 1.5-2 Vrms).  The output of the chip set then fed in current ("I") mode, with a discrete current to voltage ("I/V") stage to the RCA outputs. Modern OpAmps will give lower output impedance, but of course discrete I/V stages do sounds better.  dB Audio Labs only says the Tranquility uses discrete class-A output stage and claims that their patented I/V stage is unique.

USB implementation is plug-and-play, no drivers needed.  To output sound through the DAC, you go to your computer's sound preferences and select output to "USB Audio DAC".  My understanding is that the implementation is adaptive not asynchronous.  Since the DAC itself is 16/48 max, and the computer will down-sample, it does not matter whether it does 96khz or 192kHz.  Although the DAC should work with any computer or device with USB audio output, dB Audio Labs used Apple Macintosh to "tune" this DAC.  Eric suggested that to get the best out of the Tranquility, you should go out and purchase a clean Mac Mini 2010 with the largest amont of RAM you can afford, replace the internal hard drive with a solid state drive, keep music in a separate high performance firewire drive (he even suggested the best unit he tested), disable unused memory resident programs and processes, connect no other USB devices, and use better software than iTunes such as Amarra or Pure Music, etc.  I was already in a process of getting a new Mac Mini to be the center of my new computer audio system so these advices came in handy in helping me optimize the computer for use purely as an audio server.  The Mini will stay and function that way regardless of whether I will keep the Tranquility or not.  But for those who do not own a Mac, or may use the computer for other tasks as well, knowing (or believing) that you are not optimizing your DAC, and the fact that it only has one type of input, may be a deal breaker.  This is clearly a niche product, but a very large niche that is, given the number of new Macs sold each month.  I also read favorable report from people with Macbooks, Windows, and even Linux machines.


Sound
Each of our definition of "vinyl" or "analog" may be different.  But if you are thinking "thick", "warm", and "laid back", the Tranquility is not that.  If you had heard decent vinyl play back, you would appreciated the fast transient, rounded-note impact, slightly forward presentation but at the same time never harsh on the ears.  The mid range would be lush without being too warm.  The frequency response would be evenly extended at both frequency extremes, and definitely not thick.  The most important aspect is the palpable life-like quality.  They just sounded more real.  The Tranquility delivers much of that promise.

I left the Tranquility running continuously, driven by my old Mac Mini 2008 without really listening to it for about 80 hours. Then I moved it to the new Mac Mini 2010 rig, replacing the Bel Canto DAC 2.5.  The Bel Canto was driving the power amp directly as it has digital volume and can function as a very good preamp.  At first I tried connecting the Tranquility direct to the power amp, but the digital volume control in iTune was very noisy especially at lower listening levels, apparently Apple's dithering algorithm is not very good.  I am alternating between two Mac OSX music player application, one is Ayrewave and the other being Audirvana.  Both are free for now, but their digital volume control over USB do not work with the Tranquility.  I understand that they will only work with Wavelength, Ayre, and Wired 4 Sound DACs.  Since the two programs are very good, I do not want to invest in programs with reported good dithering such as Amarra and Pure Music at the moment.  So in order to correctly judge the sound of the DAC without the nice and the nasty of a preamp, I resorted to LDR type passive preamps because of their well-known transparency.  I alternates between George's Lightspeed attenuator (which is super transparent) and DIYparadise's EVA2.  These provided volume control for the DAC.


The first thing that comes to mind after the swap is the opening up of music.  There was more "air" to everything.  The Bel Canto's presentation was somewhat denser and slightly compressed by comparison.  The mid range, not only volcals but everything else including background instruments, was very clear, smooth and liquid with the Tranquility.  Many people were saying the midrange of this DAC is like mercury, I now know what it's like.  Everything seemed to sound easier on the ears even with rock and electronic music.  All this did not come with smearing of sharp transients.  Macro dynamics were extremely fast and instantaneous.  The music seemed more real and sounded less hi-fi.   


The sound stage seemed to "float" and separation of instruments are placed more distant from each other.  However, specific placement of instruments were less focused.  There were  haloes surrounding the instruments.  In more complex music, the tonality and palpability were superior to the Bel Canto, but you couldn't pick out the instrument clearly as before.  Overall, the soundstage seemed more believable.  The stage was not particularly deeper nor wider, but they were higher in scale.


The high end of the frequency spectrum is harder to describe.  It is very extended with plenty of air.  The highs were relaxed and some tracks with lots of zings are less pronounced, but at the same time you do not have the feeling of high frequency roll off.  The sharp edges (cymbals etc) were rounded but with impact, you could hear the stick touches the metal.  It had clarity without any trace of  harshness.  This is a quality only high performance DACs can achieve (the Weiss has similar qualities).  I guess dB Audio Labs might have designed this DAC with a low order filter as opposed to a brick wall filter.  


Bass was tight and controlled.  However it lacked the slam and weight of the Bel Canto.  There is noticeably less energy down there and it seems to be slightly rolled off.  The fundamentals were there and it fits nicely with the Tranquility's overall presentation, but if you are a bass buff, you might find this slightly less than ultimate.  However, it may be the case that there was an impedance mismatch between the DAC and the passive volume control.  (Eric suggested that the input impedance of the preamp should not be less than 50k ohms, the Lightspeed's impedance varies depending on the attenuation). 

Over the past week, I also had on hand the excellent Weiss DAC202 firewire DAC for comparison.  The DAC2o2 was connected through firewire over normal cable.  I copied and played music files directly from internal SSD drive to free up the firewire port.  All I can say is that the $6,670 DAC202 is superior to the Tranquility in many areas, but could not beat the Tranquility's mid range which was clearer, smoother and more liquid like.  It is a mid range to die for.  However, it could not match the Weiss's "cover-the-whole-wall" scale, refinement, and super articulate bass, the latter is even better than the Bel Canto.  Micro-dynamics while very good can not touch that of the Weiss.  But hey, it's three times the price!


As reported, high resolution music are down-sampled to either 44.1 or 48kHz.  I am happy to report that even with Hi-rez, all my comments above are still valid vis-a-vis the Bel Canto.  The files played fine and actually sounded better in those areas via the Tranquility.  I never heard a better sounding Jazz at the Pawnshop (88.2khz version) before.


Conclusion
The Tranquility is one of those niche products.  If you are planning a computer-based high end stereo and can live with having nothing but computers to stream music, you owe yourself a listen.  It gives you fatigue-free listening experience rarely achieved by any products regardless of price.  If you hear the clarity of its highs and liquidity of its midrange, it's really hard for you to go back.  For me the Tranquility is a definitely keeper and a match made in heaven for my new Mac Mini, so I won't be claiming that 30-day return policy.  
Highly recommended!

Red:Tranquility SE    Blue: Weiss DAC 202