I2S Input - Is It Better?

I think think you need a special cable, even though it looks like an HDMI cable.  As to whether or not it’s better, let your ears be the judge

It's a regular HDMI.  Some use an RJ45 connection. 

Generally the i2s output will yield a more accurate, cleaner sound. Tighter imaging and placement within the soundstage. Bass tends to get more defined.

This can come at the expense of sounding lean. 

Unfortunately there aren't many audiophile type HDMI cables as they are mainly for video

It depends, it looks like an HDMI cable and some companies use the same pin out but leave some disconnected. Some use their own pin out so you need to look in you manual it should show you. If they're both the same brand they will probably work together if not you might have to open them up and set jumpers. 

Unfortunately there aren't many audiophile type HDMI cables as they are mainly for video

Why, sure there is 
The following Audiophile Cable companies make HDMI cables
Acoustic Zen
Analysis Plus
Audioquest
Chord 
Crystal
Dh Labs
Furutech
Harmonic Technologies
Kinber Kable
Purist Audio Design
Straightwire
Van Den Hul
VooDoo Cable
Wireworld Cable Technology
Black Cat Cables
Nordost
Morrow Audio

and that is not all

As I understand it, one must make sure that with HDMI I2S connections the pin orientation on both devices to be connected are the same. 

Actually it is hard to tell if I2S is actually superior for there are very few devices for sale that go directly into an I2S connection--that is other than those that convert either spdif or USB to I2S. A quality DAC should already have quality spdif and USB inputs with the conversion to I2S done internally.

Some DAC I2S connections use ethernet connectors; some use HDMI cables. Mine uses both. The ethernet cables are fairly easy for an amateur to alter to meet I2S needs. Some units that feed into I2S have a bunch of dip switches so that no specially made up HDMI cable is necessary.

But I2S, which is how a DAC communicates internally, has never been much use to audiophiles as there are very few units that feed directly into it--the reason being that there are so few DACs with an I2S input. There are some bridges feeding I2S that are relatively expensive and one reasonably priced that is not a terribly high performer. So all the R&D goes into those feeding USB or spdif.

So theoretically yes, but in practice no.

Who ever thought this could be so confusing?  Anyway, I ordered a Holo Audio May DAC and my CD transport is a Jay's Audio CD-2MK2.  The transport has an I2S output and the DAC has an I2S input.  I'm going to contact the two manufacturers to see what they recommend.  I'll report back if I find out anything useful.  

Contacting the manufactures is the best thing to do. If I had I2S capability on both devices I would want to try using it.

Go to the Jay Audio CD-2MK2 page and copy the pinout of the I2S, send it to the Holo May support and they should be able to tell you the position the dip switches need to be. I personally don’t see the point since the player only puts out redhook any of the connections would be fine I would use the AES/EBU.

I wrote to Tim Connor at Holo Audio about this and here is what he wrote in response (My question was in regards to using a Jay's Audio CD Transport with the May DAC):

"The May dac has two i2s inputs and they are both configurable to any i2s pin out if you want. But come standard holoaudio type pin out which is indentical for psaudio except dsd channel left and right are reversed. But if you are using cd the dsd channels are not used anyhow. Most likely it’s psaudio i2s pinout. But you can refer to the manual for the jays Device.
Also the May dac has a Manual too, it’s downloadable from the product page. And explains how to set up i2s if you need to change it to something different."

I also asked Tim if there was any significant improvement using I2S vs. AES/EBU and here is what he said:

"Personally I’m all about i2s. It’s the best all around. With a good Hdmi i2s cable it’s definitely a step up. The aes/eBu is as good as spdif gets bit imo Spdif is a bit dated. We have overcome a lot , if not all usb shortcoming and i2s is just beyond that. I personally use i2s always"

My May DAC is supposed to arrive next week.  I'll plan to start using the AES/EBU input with my transport at first.  Once I get familiar with the sounds I will probably give the I2S a try.  

Cheers

The best thing to do is try out both. I asked mojo audio if they could add an i2s input to their dac and they felt strongly that it would be a mistake. The basic gist of the reasoning is that if we know clock timing/syncing is essential, why would you use a technology that has three separate data streams that all need to be synced for perfect audio? This cued me to try my streamer's SPDIF output and it was indeed superior to the i2s. And that was with a 15yo monster cable vs a mid-range well-reviewed hdmi. Obviously ymmv.

Agree with what Tim said (really good dude). 

Broadly speaking AES/spdif will have a less focus in terms of imaging and staging, but the tend to have a bit more body/warmth. Bass will be a bit more bloated as well. 

I find USB in the middle and i2s on the opposite end - presenting a much cleaner sound but can be lean if your equipment downstream is. 

For a long time, I used a USB cable between my Innous Zenith streamer and PS Audio DSD DAC.  A few years ago, I purchased a Matrix X-SPDIF 2 DDC and a i2s HDMI cable.  I inserted the Matrix between the Zenith and DDC.  There is a very noticeable SQ improvement. 

@snackeyp You should definitely try i2s.

I have a metrum acoustics ambre streamer with spdif, AES and I2s outputs and matching metrum DAC with all of those inputs.  I can easily switch between them and find I2S the best sounding but not by much.  The bass is a little tighter and soundstage a bit larger and the sound a bit more dynamic so I prefer the I2s connection but they are all very good and generally similar sounding so not a deal breaker by any means.