Does this dac exist?

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.

Steve N.
Empirical Audio

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 N.
Empirical Audio

"1. Can the EA Overdrive dac be controlled with Amarra or Pure Music when using the async USB input?"

Yes.

"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.

Steve N.
Empirical Audio

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.

Steve N.
Empirical Audio

"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....

Steve N.
Empirical Audio