About two and a half years ago, I reviewed PS Audio’s first generation of its Bridge, an optional small board that snaps into the back of PS Audio’s highest end DAC (which at the time was their PerfectWave MKII), that allows one to use an ethernet cable as input for streaming audio files to the DAC. It serves as an alternative option to the more common digital inputs such as S/PDIF and USB, and can also be used to easily set up a DLNA (Digital Living Network Alliance) based NAS (Network Attached Storage music server), thus avoiding being tethered to a stand-alone computer, while at the same time allowing all devices on your network to have access to the music files.
Soundwise, on my system, it bested any other digital input including USB cables costing hundreds of dollars: an ethernet cable on the other hand only costs several dollars (now days as cheap as $3.00 for a 1 meter cable). Additionally, an ethernet cable’s length has no effect on sound quality as does (say) USB; one can use a 3 foot cable or a 50 foot one. Ethernet thus became my reference method of streaming. Keep in mind that when a Bridge is installed one can still use the other digital inputs/modes (such as USB with a computer, or S/PDIF with a CD player or transport, for example); you can choose among all the various options on the remote or on the front monitor of the DAC. The additional option ‘Bridge’ is the ethernet option. The main point is that you have the additional ethernet option if you so wish to use it. It is a true luxury.
Only a handful of other DACs in the world offer the ability to use ethernet, with varying methods/success of trying to accomplish it. It is not trivial. The Bridge, for example, has a computer and their ‘Digital Lens’ technology built into it, so it actually is the player (renderer) when the digital files are sent to it over ethernet. Mighty impressive.
Admittedly the original Bridge had some problems; the one most complained about was its inability to play gapless. It also sometimes (seemingly at random) could skip during playing high resolution files (such as PCM 24/192) depending on what server software or controller software or computer one was using, and the artwork sometimes did not display on the DAC’s front monitor as it should. In short it required a bit of computer savviness to get it working at its best– it was a bit finicky. But as one who enjoys tinkering with computers, I was deeply impressed and mesmerized by the sound quality and even got the Bridge to work with a direct crossover ethernet cable from my Mac-Mini to the DAC, thus avoiding the use of an internet connection, an internet hub—and very expensive USB cables.
To address the aforementioned flaws, PS Audio took the constructive criticism very seriously and spent the next 2 years on an upgrade: Bridge II, the topic of this review. In the meantime, before the release of Bridge II, PS Audio released their new DirectStream (DS) DAC which has replaced their MKII and which I now use as my reference DAC; it can even play DSD files. The DS can be used with the original Bridge, and I had it initially set up that way, but after awhile I went back to using USB mode since it sounded better to me on the DS, had no finicky problems, and my dear daughter wanted to hear The Beatles gapless album ‘Love’!
Then came the release of the Bridge II ($899.00; $599 with a Trade-in of the older Bridge). PS Audio kindly allowed me to keep both Bridge models during my assessment. As stated on the PS Audio website, ‘Bridge II has a number of advances to the original, including: gapless play, stable connectivity, far better sound, lower jitter, higher speed architecture.’
After extensive testing, I report here that I fully agree with their statement and will expand upon this achievement in what follows.
Some technical background: The advantages of an ethernet connection
Bridge II can handle PCM resolution up to 32 bit/192kHz, and DSD via DoP. Its core processor runs at 500mHz and it has 256MB of high speed DDR (double data rate) memory. When you stream a file to it with an ethernet cable, the Bridge II itself puts the packets back in order and then converts to I2S (Integrated Interchip Sound), the serial bus interface required by all DACs. This is not a trivial matter. As explained by PS Audio, that I2S data is then ‘clocked out with extremely low jitter fixed frequency asynchronous clocks and into the DAC through high speed buffers isolated by a separate power supply.’
Ethernet is a one-way set of data without clock information–just a bunch of packets sent to anything that simply has to put it back in order (re-assemble it). USB, on the other hand, is a two-way communication with timing involved. That timing with USB causes problems for audio streaming that have to be remedied. That is why, when one uses (say) a Mac Mini with USB, various upgrading and peripherals are required to get optimal sound: a high-end separate linear power supply, an expensive short in length USB cable, and superior sounding player software (such as JRiver) for example. The Mac Mini (or any computer) when using USB struggles to access memory allocations, and has to deal with serious timing and jitter issues. More generally, that is why stand-alone high-end USB based music servers are expensive (they can be well over $5000).
But when using ethernet it makes no difference. To send out ethernet data (via a PC or a MAC or a NAS), little expense is required beyond ensuring the device used has enough speed, enough disk space and appropriate sofware: Once the data is sent, it does not matter what device sent it, it will have no eaffect on the quality of the sound at the other end (DAC).
And the quality of the cable is irrelevant too (I am using a $3.00 ethernet cable). As PS Audio CEO Paul McGowan told me via email when I asked him related questions:
Ethernet data can be sent without any change in sound quality around the world or two feet away. That is because the packets haven’t any timing information associated with them. They are just chunks of data that can come slowly or quickly without affect. The data is unremarkable and agnostic as to how it is delivered. And likewise the quality of the cable that carries the data matters not. The same cannot be said for any other type of data transmission. USB, S/PDIF, Coaxial, even TOSLINK are susceptible to sound differences according to the media they travel through.
But admittedly there is a bit of sleight of hand here: Yes, the ethernet stream has the huge advantage of being insensitive to the device/software/cable sending it to the DAC and the ‘sound’ is not effected in any way. But once it hits the DAC then it becomes the DACs job to essentially do what the expensive USB music server/computer does. In the DS case, it is the Bridge II that does all that magic involving timing and jitter issues. (Recall that it has a computer built into it.) All the more impressive.
Using the Bridge II
I used my (Mojo Audio upgraded) Mac-Mini with a crossover ethernet cable between it and the Bridge II with JRiver Media Center 20.0.132 as the audio software. Keep in mind that to use ethernet/Bridge II you must use a player software that utilizes both DLNA and UPnP (Universal Plug and Play); iTunes for example will not work. JRiver also can convert DSD to DOP format on the fly, making the streaming of DSD to the DS DAC possible.
I was able to stream music both via USB and ethernet simultaneously by just clicking on the DAC’s remote control back and forth for comparison in sound–a very convenient feature. And I even used a USB Regen and a AudioQuest Jitterbug USB filter to help USB out as best I could for comparison. I used several high-end USB cables including my reference favorite. In other words I did my best to give USB the upper hand. I summarize below my assessment of four main areas that were of concern on the original Bridge, and then discuss the most important one–sound quality–in the next section.
1. Front Monitor Display: One of the nice features one gets with Bridge mode is that the album cover (in color) and name of the album, and name of the track you are playing is displayed on the front monitor of the DAC together with other information (also included in the other modes) such as how much time has elapsed on the track, the volume level and the type of file that is playing such as PCM 16/44.1 or DSD 64. This feature works beautifully now. I noted no problems with this feature after extensive use of all kinds of files including DSD and 24/192 PCM. When you click on a track when using Bridge II mode, it takes a delay of about 30 seconds until the front monitor on the DAC shows the album cover. But the other information is displayed immediately, and the music plays right away. Perhaps some will quibble about this 30 second delay in showing the cover, I am not one of them. Typically I am sitting on the couch or at my kitchen table and from such a distance I can’t see the monitor in such clarity anyhow. Or one is using a controller such as an iPad for the visuals/info instead of the front monitor.
2. Speed: The Bridge II is whipping fast: When changing from one album to another regard- less of file type, the transition (sound) is almost immediate. I tried switching between PCM at different resolutions, between PCM and DSD and back again. No problems.
3. Gapless: Gapless works perfectly now. As my main test case I used the Beatles ‘Love’ album. I even borrowed the LP version from a friend and played that on my turntable for comparison.
4. Stability/skipping: I had no problems. If ever something went wrong, it was always (in my testing) due to a software issue with the JRiver; or a software issue with JRemote. As I learned: Once you get the software settings up and running the way you like, do not turn off (unpower) the computer or the DAC unless you absolutely must. Currently, for example, I have left all on for 1 week and the Bridge II has been playing flawlessly.
The Bridge II did not color the sound on my system. It offered extraordinary transparency. As compared to USB it offered more clarity, neutrality, tighter bass, and air. What USB offered with some of its best cables could be (and still is) very seductive with a sweet softness and a smoother and more forward fullness (but which can at times yield a fluffiness that covers details); Bridge II had the perfect balance and did so with elegance, finesse and politeness (it does not boast). As a wine analogy: imagine a glass of extraordinary red wine elegantly displaying its native terroir of complexity of minerals, flowers, various fruit nuances, spices and so on (Bridge II). Now recall how that same wine smells/tastes when you have a very minor cold (USB).
I, of course, played over and over many of my ‘reference recordings’ such as the classic 24/192 Norah Jones ‘Come Away With Me’ which had caused problems with the original Bridge (but now no more), ‘Trilogy’ by The Chick Corea Trio at 24/96, Janos Starker playing Bach Suites for Solo Cello, Beethoven Piano Concertos 3 and 4 (Peres/Harding), Pierre-Arnoud Dablemont playing Beethoven piano sonatas Op. 27 & 28, ‘Love is the Thing’ by Nat King Cole, various recordings by Bill Frisell and DSD files such as ‘Art Pepper Meets The Rhythm Section’ (which actually sounds better in mono).
But I also thought it important to start from scratch with something new to avoid a bias I might have in the way I am used to hearing a piece I know so well. Perhaps my favorite album in that regard for comparison was one I have only recently discovered: ‘The Astounding Eyes of Rita’ by the Tunisian oud player and composer Anouar Brahem. (Instruments: oud, bass clarinet, bass, and the ancient arabic traditional drums–darbouka and bendir.) It is lovely, soothing, charming and exotic. It is a superb recording that I think quickly demonstrates what I articulated above.
Once again, but now on the new PS Audio DirectStream DAC with the Bridge II, an inexpensive (now only $3.00 for 1 meter Cat 6) ethernet cable bested expensive high-end USB cables, and there were no hiccups. I don’t mean to say that the difference in sound quality was extreme; it sometimes took careful listening but often was immediate; USB at its best sounded outstanding also. But in the end, ethernet sound quality won me over — whether it be via a 3 feet long cable or 50 feet. And although the Bridge II’s price of $899 might seem steep to some, don’t forget that it is essentially doing, among other things, much of the magic and work that a very high-end music server (costing thousands of dollars) does — and it only weighs a couple of ounces. Quite something–squared. Highly recommended.
Further information: PS Audio