An Empirical Audio Off Ramp or M2Tech Evo USB converters have I2S and would work with those players.
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The EA Overdrive has I2S in, but according to the manual:
The Overdrive I2S input is compatible with the Empirical Audio I2S standard. It can be driven with a Pace-Car or an Off-Ramp.
So it sounds like in order to use the I2S input on the Overdrive, you must go:
computer -> USB -> Pace Car/Off Ramp -> I2S -> Overdrive dac.
I would like to go:
computer -> I2S -> dac.
As far as the M2Tech Evo, it is a USB converter, like the EA Off Ramp. What I am looking for is a dac that accepts I2S from the computer without the need for an additional converter.
Here is what the Wyred DAC-2 manual says about its I2S input:
The W4S DAC-2 is equipped with a balanced I2S connection via HDMI. Please note that the DAC will NOT offer playback from typical HDMI output connectors found on many DVD players (or similar devices), and damage can occur if connected to such. The HDMI connector was uses for speed, noise rejection, and signal purity. With-in the connection, there are balanced versions of the I2S interface that offer superior connectivity to any source which can output the signal. At the time this manual was written, the only component capable of outputting the balanced I2S signal is the PS Audio Perfect Wave Transport. In the very near future W4S will be coming out with a modification program which will offer proper circuitry to be added to many components for those who wish to benefit from this jitter-free connection. Please contact us for more information and current options.
So the DAC-2 would not currently allow me to go:
computer -> I2S -> dac
Also, the DAC-2's I2S input is via HDMI. I should have made clear that I am primarily interested in finding a dac that allows for I2S over ETHERNET. In other words, I would like to go:
computer -> I2S via ethernet -> dac
The only dac I know that is currently capable of this is the PS Audio PerfectWave dac, but, as I mentioned in the OP, it cannot be controlled with non-proprietary software like Amarra and Pure Music.
I don't know whether I2S has the potential to sound better than asynchronous USB, but I suspect that the answer is: maybe.
It seems like there are two basic consideration for the quality of the computer/dac interface.
1. The correct data.
2. The correct timing.
It is my understanding that I2S over ethernet (a) would allow for error correction; and (b) would be very low in jitter (jitter free?). If that is true, it would seem to be the most promising interface between the computer and dac.
In addition, it is my understanding that I2S is the native interface of most dac chips. If that is true, then there would seem to be an inherent advantage in sending an I2S signal from the computer to the dac, avoiding conversions to USB, S/PDIF, etc..
I understand that implementation is everything, so that the use of I2S does not guarantee good performance. It just strikes me as the most promising approach for SQ and future proof-ness (to the extent that exists).
I am happy to be wrong about any of this.
I don't know whether I2S has the potential to sound better than asynchronous USB, but I suspect that the answer is: maybe.
1. Again, you always need an audio device somewhere on the line (Ethernet, USB, Firewire, PCI) to convert your audio files to I2S. There is no such thing as direct I2S from computer.
2. Why Ethernet? My understanding is that latency is much higher than USB and Firewire.
3. You can get I2S from any PCI audio card and some USB converters.
4. As already suggested, try the M2tech EVO I2S out connected to a DAC with I2S input.
5. There are 3 major audio data formats that DAC chips take. I2S is one of them, but not my favorite.
Bryon - I2S does not come direct from any computer. Nor is it related to Ethernet. Empirical Audio, as well as Northstar and Ayon use RJ-45 connector for I2S. Has nothing to do with Ethernet. Just using the connector.
Likewise, PSAudio uses HDMI connector for their "differential" I2S. Has nothing to do with HDMI spec. They are just using the connector.
I2S will generally deliver the lowest jitter to most D/A chips because this is their native interface, however an async reclocked USB interface driving I2S to a D/A chip in a DAC is about as good as you can get. This is assuming that the clock used for the USB interface is very low jitter, and the design and implementation is executed well.
Alex - I am interested in a dac that connects to the computer via ethernet so that (a) the data delivered to the dac can be error corrected; and (b) the computer can be placed at a significant distance from the dac (30 feet+).
Steve - Thank you for clearing up something that was confusing me -- I was under the impression that I2S and ethernet were somehow related. From your post, and from more reading, I see that they are not. So really what I'm looking for is a dac/computer interface that...
(1) ...is very low in jitter.
(2) ...allows the dac to communicate with the computer such that the data delivered to the dac is error corrected (as ethernet can, as I understand it).
(3) ...allows the computer to be placed far away from the dac (30 feet+).
(4) ...allows for the use of software, like Amarra or Pure music, that is not proprietary to the dac.
I don't know if such a thing exists, or could possibly exist, which is the reason for the OP.
Thanks for you help.
Bryon - the problem is that Microsoft and Apple have not yet put any audio streaming software out that interfaces with networking. This may never happen, but we hope it will. This is the only thing that will enable third-party software packages like Amarra to work with a networked DAC.
Until this happens, you are stuck with custom software for each networked implementation, such as Sonos or Squeezecenter etc..
If you are needing 30 feet, you can actually use a USB cable. There is a special build for this length. You can also split the cable length between the I2S and the USB cables, but I would not recommend making the I2S cable longer than 2 meters. It has to carry signals to almost 50MHz.
It is really more important that you like the sound of the particular DAC. Trying to buy components based on specs or what chip is used never works IME. You should definitely go for an adaptive USB interface with low-jitter clocks however. There will be one compatible with PSAudio I2S soon.
Steve - Thanks for the explanation and the advice. FWIW, I agree with you that a person should not choose a dac based on specs or chips.
What I am trying to do is maximize SQ (low jitter, error correction), flexibility (distance of computer to dac), and functionality (compatibility with Amarra/Pure Music). The thing I am most willing to give up is the long distance of the computer to the dac.
A few questions for you, Steve:
1. Can the EA Overdrive dac be controlled with Amarra or Pure Music when using the async USB input?
2. Does the Overdrive require drivers with a Mac, or is it like the Pace Car in that you plug it in and it automatically shows up in Preferences>Sound>Output?
3. Is the Overdrive compatible with Mac's "aggregate device" function, so that the outputs of a software-based crossover can be sent to two different dacs simultaneously?
"1. Can the EA Overdrive dac be controlled with Amarra or Pure Music when using the async USB input?"
"2. Does the Overdrive require drivers with a Mac, or is it like the Pace Car in that you plug it in and it automatically shows up in Preferences>Sound>Output?"
It requires a driver be loaded. All of my Async USB interfaces need this.
"3. Is the Overdrive compatible with Mac's "aggregate device" function, so that the outputs of a software-based crossover can be sent to two different dacs simultaneously?"
I have heard of others using this with Off-Ramp 4 etc.., but I have not been successful when I tried it. I'm not that experienced with Mac.
I2S is not an external standard primarily because most manufacturers that have added it (about 10) implement it differently, and usually poorly. The designers simply dont understand transmission-line effects and termination techniques. S/PDIF standard was created by a standards committee, mostly staffed by Sony and Philips.
It's a lot like Word-Clocks on transports and DAC's. Very few of them are implemented well and it can be hit and miss whether they work well or at all. You dont know what signal levels are expected and the termination is questionable or not there at all. There was never any committee to my knowledge to standardize word-clocks.
The reason for the variability in I2S, besides the fact that no manufacturer seems to want to be a follower, is that most of the signals in I2S are high-frequency with fast edge-rates. Almost 20 times higher frequency than S/PDIF in some cases. Guys that have been primarily designing analog and maybe copying a little digital are lacking in experience to deal with this. This is the reason that some designers denigrate I2S on the forums. They dont want anyone to know that they are not competent enough to pull it off, so they call it a bad thing.
For someone with a digital background and experience with high-speed signalling, this is like falling off a log.
But how come I2S is still not the digital standard for a CD transport and DAC interface
Mostly because it does not provide copy right protection, and other user programmable features.
As I mentioned, I2S is just one of the standards a DAC chip can take, such as MSB and LSB, but let's focus on I2S as you know it.
I2S contains 4 signal lines; data and 3 clocks. S/PDIF contains exactly the same unaltered signals, less the 4th line, the Master Clock. The real fault of S/PDIF comes from the PLL used to "recover" the Master Clock inside the S/PDIF receiver. This usually results in relatively very high jitter level and poor sound quality.
Providing a high-quality external Master Clock, or re-clocking solves all issues with S/PDIF. In my experience, such solution is not even a bit worse than I2S.
Back to your original post - If you want to use computer software, then you either have to
a) install a sound card with i2s output
b) use a USB to i2s converter - there are several of these, then feed the i2s signal to the DAC of your choice.
In my opinion it is better and more practical to place your computer next to the USB DAC (pref with async protocol like Empirical Audio's) and control the computer remotely.
I use a Mac mini, controlled via screen sharing from another computer, feeding a USB DAC, both are placed on my hifi rack.
Steve/Alex - Thanks for your observations. It always amazes me the extent to which technologies are determined by institutional momentum, short term market forces, lack of cooperation and planning, etc.. Computer audio hasn't quite emerged from the era of kludges. Having said that, I love the ease of use in my computer audio setup, and would never go back to discs. I just wish technologies would progress a little faster in this area.
Steve - Did you mean to say "asynchronous" USB here, or are you recommending adaptive USB?
Sirotseta - Thanks for your advice. Mac mini + USB dac close to the computer + screen sharing is how I'm leaning at the moment.
Do you happen to know if the Mac mini can be controlled by an iPad?
"Steve - Did you mean to say "asynchronous" USB here, or are you recommending adaptive USB?"
I meant to say Async, not adaptive. I have abandoned Adaptive, closeout items only. Async is more expensive and requires 2 clocks to support all sample-rates, but it's worth it.
This market is advancing so quickly that I was surprised to see new DAC's being debuted at CES that were still adaptive 24/96....
Just to add to Alex's reply.
If you use iTunes or music player that dock to iTunes such as Pure Music or Amarra, you can use the free Apple's Remote App for iPad to control it.
To take full control of another computer on iPad, I use "Screens App".
Fidelia has its own ipod interface. Audirvana can be controlled by apple small white remote, and also by Rowmote App over wifi.
I used to be a transport nut, and really thinks that transports sounds as different as DACs do. Now I'm converted, and use only Mac mini as transport via async USB. It's better than my (older) Esoteric and Theta machines. The only thing spinning in my rig now are vinyl.
Srwooten - I have given serious consideration to the PerfectWave dac, but I don't like the idea of being limited to PS Audio's proprietary software. One of the reasons is that I would like to be able to utilize plugins for EQ, for example. Do you know if the PS Audio software will support plugins, like Pure Music does?
BTW, I commented in my last post that I wished technologies in computer audio would advance faster. What I really meant is that I wish they would *converge* faster. It is the lack of standardization that is a bit confusing and sometimes frustrating.
You are not limited to PSA's software at all. In fact I don't use it. Their music server software is still BETA.
J River has plug ins but they will not work with DNLA yet. I do not know if it ever will, but it seems to me to be a logical direction for them to move.If you use plug-ins via your software through any PWD input other than the Bridge they will work.
Srwooton - Sorry, I should have been more explicit. In my second post on 3/16, I wrote:
...what I'm looking for is a dac/computer interface that...
If my understanding is correct, the PS Audio PWD, when using the Bridge, provides for the first three items above, but not the forth. That is what I was trying to say in my last post.