Arcam rDAC Asynchronous USB DAC Review

A $479 high quality asynchronous USB DAC would have been available only in one's dreams a couple years ago. In mid 2010 UK based Arcam released its rDAC that includes a single USB input, with licensed dCS asynchronous USB technology, optical and electrical S/PDIF digital inputs and an optional wireless dongle. As many Computer Audiophile readers know getting digital audio to an external DAC, asynchronously or otherwise, is merely step one and does not make or break a DAC's performance. The rDAC certainly succeeds at this first step, but is not faultless from start (digital input) to finish (analog output). Externally the design is flawless and very Apple-esque. The industrial looking aluminum enclosure fits right in with a number of Apple's current products. Overall the very good sonic performance, reasonable price, and great design are a winning combination for the Arcam rDAC.

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<b>External and Internal Design Details</b>

Arcam borrowed a page directly from the <a href="http://en.wikipedia.org/wiki/Jonathan_Ive">Jonathan Ive</a> school of design when developing the rDAC's enclosure and packaging. Opening the rDAC's package was similar to opening an Apple product's package. I immediately felt like the product was a cut above the rest. Like Arcam really took its time and put serious thought into this product and I hadn't even plugged the unit in to the wall. The somewhat substantial smooth aluminum enclosure oozes quality with every touch. A nicely designed rubber base prevents the silver aluminum from scratches and from scratching the material of its final resting place. Not only is the design full of form but it also has function. A single circular button placed front and center on top of the rDAC makes it nearly idiot proof. Pressing this button changes the active digital input. If the selected input is connected a slim green light illuminates above the input's label on the front/top edge. Unconnected inputs illuminate red only when selected, otherwise remain dark saving one's listening environment from the lighted Christmas Tree effect. The input layout on the rear of the rDAC is well design and simple. Well labeled horizontally placed inputs enable easy cable switching even in a cramped component rack. There's nothing worse than inputs aligned vertically when the top one or two inputs are already in use. Good luck finding the bottom input without a <a href="http://www.amazon.com/Medport-Telescoping-Self-Examination-Mirror/dp/B000092OX3">telescoping self examination mirror</a>. Fortunately the rDAC doesn't have this problem.

<center><img src="http://images.computeraudiophile.com/graphics/2010/1122/rDac.jpg"></img> <img src="http://images.computeraudiophile.com/graphics/2010/1122/rDac-back.jpg"></img></center>

Internally the Arcam rDAC uses the well respected <a href="http://www.wolfsonmicro.com/products/dacs/WM8741/">Wolfson 8741</a> DAC chip. Thus the rDAC supports 16 and 24 bit word lengths and all sample frequencies between 44.1 and 192 kHz via coaxial input. Optically the rDAC supports from 32, 44.1, 48, 88.2 and 96 kHz although the user manual incorrectly says only 44.1 and 48 kHz are supported. The asynchronous USB input supports from 32 to 96 kHz and all frequencies in between. According to Arcam the wireless dongle supports 16 bit / 44.1 kHz only. The wireless dongle was unavailable during the review period.

The rDAC's external 6V power supply is nothing to write home about. This switching supply is no better or worse than most other switching power supplies used with components in this price range. I'm not exactly sure what adding a linear supply would have done to the MSRP of the rDAC but I bet it would've moved it into the next tax bracket. Computer audiophiles shouldn't expect the world for less than $500.

The main issue I have with the rDAC is its lack of <a href="http://en.wikipedia.org/wiki/Galvanic_isolation">galvanic isolation</a> between the computer and DAC. A computer is an electrically noisy harsh environment compared to high-end audio equipment. Galvanic isolation stops electric current flowing directly from the computer into the DAC. Some high-end manufacturers use optical (non-S/PDIF optocoupler) isolation while others transformer couple all electrical digital inputs. The rDACs directly coupled electrical digital inputs are not show-stoppers in and of themselves as it's entirely possible to achieve very good sound with or without isolation. I found this to be true when switching between my <a href="http://www.computeraudiophile.com/content/Computer-Audiophile-Pocket-Server-CAPS">C.A.P.S.</a> server and my Mac Pro server both via USB. Connected to my C.A.P.S. server a very noticeable garbled hum type of noise was audible through my Verity Fidelio loudspeakers. Upon switching to the USB output of my Mac Pro the noise was completely gone. One could say that my computer was the problem. While I won't disagree, I do think a galvanically isolated USB input would have removed the noisy computer differences from the equation. It's nearly impossible for Joe Sixpack to know if a direct coupled component like the rDAC will be an issue in his system. That said, if Arcam galvanically isolated the inputs the sonic results would have been completely predictable from one installation to another. One sure way to isolate a noisy computer from audio components is to use an optical digital connection and TosLink cable. This cable breaks the electrical connection and stops all electrical current from flowing directly to the DAC.

<b>Using The rDAC With OS X 10.6.5 and Windows 7</b>

During the review period I used the rDAC with Windows 7 and OS X 10.6.5 based computers. When using Mac OS X on a MacBook Pro and a Mac Pro I used iTunes in conjunction with <a href="http://www.amarraaudio.com/">Amarra</a> version 2.1. The rDAC was as simple to use as any other DAC connected to a Mac. I selected the rDAC as my output device after connecting the DAC for the first time and that was it for configuration. Using Windows 7 with <a href="http://www.jriver.com/">J River Media Center</a> version 15 took a little trial and error to achieve the best results. I settled on J River's WASAPI - Event Style output mode and 100 milliseconds as the hardware buffer size. The rDAC didn't function correctly with ASIO or Kernel Streaming in my system. I highly recommend USB DAC users try WASAPI - Event Style as it has some <a href="http://www.computeraudiophile.com/content/New-J-River-WASAPI-Event-Style">great advantages</a> over standard WASAPI. Once J River Media Center was configured to work best with the rDAC I didn't adjust the settings for the remainder of the review period. New computer audio users should be assured that once Windows is setup correctly it needn't be messed with to continue obtaining great sound.

<b>Listening To the rDAC</b>

During the review period the rDAC was connected to a Benchmark DAC1 PRE for evaluation via headphones (Sennheiser HD600 and Grado RA-1) and loudspeakers. The DAC1 PRE was connected to a McIntosh MC275 amplifier and Verity Fidelio loudspeakers. All volume attenuation was handled in the analog domain by the DAC1 PRE.

I listened to a aide range of music through the rDAC.

<ul>

<li>Ben Harper - <a href="http://www.electricfetus.com/rel/v2_viewupc.php?storenr=227&upc=72438393202">Welcome to the Cruel World</a></li>

<li>Boz Scaggs - <a href="http://www.electricfetus.com/rel/v2_viewupc.php?storenr=227&upc=69826840002">But Beautiful</a></li>

<li>Brother Ali - <a href="http://www.electricfetus.com/rel/v2_viewupc.php?storenr=227&upc=82625701132">Us</a></li>

<li>CéU - <a href="http://www.electricfetus.com/rel/v2_viewupc.php?storenr=227&upc=65703611602">Vagarosa</a></li>

<li>Christina Aguilera - <a href="http://www.electricfetus.com/rel/v2_viewupc.php?storenr=227&upc=88697714912">Bionic</a></li>

<li>Dallas Wind Symphony - <a href="https://www.hdtracks.com/index.php?file=catalogdetail&valbum_code=HD030911111229">Crown Imperial (24/96)</a></li>

<li>Joe Pass - <a href="http://www.amazon.com/Virtuoso-Joe-Pass/dp/B000056MU4/ref=sr_1_3?ie=UTF8&s=music&qid=1290414469&sr=8-3">Virtuoso</a></li>

<li>Laurence Juber - <a href="http://www.itrax.com/Pages/AlbumDetails.php?aID=AL_106221839745f1fa089b92c">Guitar Noir (24/96)</a></li>

<li>Mark Knopfler - <a href="http://www.amazon.com/Sailing-Philadelphia-CD-DVD-Audio/dp/B00069A5GE/ref=sr_1_1?ie=UTF8&qid=1290414583&sr=1-1">Sailing To Philadelphia (24/88.2)</a></li>

<li>Nat King Cole - <a href="http://www.musicdirect.com/product/86663">The Very Thought of You</a></li>

<li>Shelby Lynne - <a href="http://www.amazon.com/Tears-Lies-Alibis-Shelby-Lynne/dp/B0039ZF86E/ref=sr_1_1?ie=UTF8&qid=1290414665&sr=1-1">Tears, Lies and Alibis</a></li>

</ul>

Most of my listening was done around 60-75 db with peaks between 85-95 db. I mention the level only because human ears are not linear as volume increases and decreases. Thus, our ability to perceive differences can be greatly affected by the volume level according to the University of Massachusetts' Alex U. Case. Great detail about this and other aspects of human hearing as it relates to equalization can be heard by purchasing a recording of Mr. Case's 2010 AES presentation titled <a href="http://www.mobiltape.com/conference/Audio-Engineering-Society-129th-Convention"><i>Equalization—Are You Getting the Most Out of this Humble Effect</i></a>.

I listened to all the rDAC's inputs extensively and by far the best sound quality was through its USB input. The other two inputs seemed to make an attempt at competing with the asynchronous USB interface, but it really was no contest. Overall sound quality through the rDAC was really good. I frequently listened to music for several hours without fatigue. From top to bottom the rDAC was a very good performer and a very enjoyable component to have in one's system. It certainly didn't hold a candle to its extremely distant relative the dCS Debussy in my system but such a comparison is poppycock.

The second best input was coaxial S/PDIF. Listening to Dallas Wind Symphony's Crown Imperial at 24/96 made it apparent the frequencies below about 200 Hz were a bit muddy via the coaxial input when compared directly to the USB input. Midrange and higher frequencies via the coaxial input were very close in quality to the USB interface and at times indistinguishable.

The optical S/PDIF TosLink interface was a completely different story. Optically connected to my Mac Pro all music through the rDAC sounded normalized and washed out. Dynamic range even sounded reduced. Instruments lacked any clear separation. I really hoped the rDAC would shine via its optical S/PDIF interface so I could forget about the lack of galvanic isolation, but this just wasn't the case.

Since I used the Benchmark DAC1 PRE throughout the review I was able to compare the performance via its adaptive USB input to the rDAC's asynchronous USB input. I specifically wanted to know if it made sense to purchase an rDAC for those who already own a Benchmark DAC1 variant. After this comparison I would not hesitate to add an rDAC to an existing DAC1 based system. The rDAC was a touch more laid back, natural, and focussed with a smaller sound stage. I preferred the sound quality via the rDAC's USB input and converter to that of the DAC1's USB interface and converter. As all review readers understand preferences aren't facts. A personal assessment of the sonic differences between these two interfaces and converters is very simple to conduct. I encourage everyone to contact an Arcam dealer and bring a DAC1 along for comparison. I can't wait to review the new Grace Design m903 with its built-in 24/192 asynchronous USB interface using Gordon Rankin's StreamLength code. It's highly unlikely an external async USB DAC will be needed to improve sonic results through the m903.

<b>Conclusion</b>

The Arcam rDAC has three big things going for it, very good sonic performance, reasonable price, and great exterior design. This level of sonic quality starting with a great async USB interface is not common for $479. Throw in the wonderful industrial design of the rDAC and the price could have been much higher. The rDAC should be a really nice addition to nearly all computer audiophile's systems. Based on my experience Mac users should have no trouble with the rDAC's directly coupled digital interfaces. I certainly enjoyed my time with the DAC partly because listening through it didn't feel like much work. We've all heard those components that make our ears bleed. This DAC is not one of them.

Product Information

• Price - $479
  
• rDAC Product Page - <a href="http://www.arcam.co.uk/products,solo,DACs,rDac.htm">Link</a>
  
• rDAC Manual - <a href="http://www.arcam.co.uk/_ugc/file/rdace_manual.pdf">PDF Link</a>
  

Associated Equipment:

<a href="http://files.computeraudiophile.com/2010/0418/Brochure_Fidelio.pdf">Verity Audio Fidelio loudspeakers</a>, <a href="http://www.mcintoshlabs.com/products/mcintosh-mc275-vacuum-tube-power-amplifier.asp">McIntosh MC275 amplifier</a>, <a href="http://www.richardgrayspowercompany.com/products.aspx?type=accessories">Richard Gray's Power Company High Tension Wires</a>, <a href="http://www.berkeleyaudiodesign.com/">Berkeley Audio Design Alpha DAC</a>, <a href="http://www.computeraudiophile.com/content/Computer-Audiophile-Pocket-Server-CAPS">C.A.P.S. server</a>, <a href="http://www.dcsltd.co.uk/product/debussy-dac"><i>d</i>CS Debussy DAC</a>, <a href="http://www.kimber.com/products/interconnects/digital/usb/bbus/cu/">Kimber USB Cu</a>, <a href="http://www.kimber.com/products/interconnects/digital/usb/bbus/ag/">Kimber USB Ag</a>, <a href="http://www.benchmarkmedia.com/system1/digital-analog-converter/dac1-pre">Benchmark DAC1 PRE</a>, <a href="http://www.kimber.com/products/interconnects/analog/select/singleended/ks1011/">Kimber Select KS1011 Analog Cables</a>, <a href="http://www.kimber.com/products/interconnects/digital/select/ks2020/">Kimber Select KS2020 Digital Cable</a>, <a href="http://www.kimber.com/products/loudspeakercables/monocle/x/">Kimber Monocle X Loudspeaker Cable</a>, <a href="http://usa.asus.com/product.aspx?P_ID=SPZfqXDJvadmFPoh&templete=2">ASUS Xonar HDAV 1.3 Slim</a>, <a href="http://www.apple.com/ipad/">Apple iPad</a>, <a href="http://www.amarraaudio.com/">Sonic Studio's Amarra</a>.