Is my HDMI audio out really an i2s connection?

Try it! Have fun. But... it is not i2s.

I run hdmi from my 1100 to a Moon 390 hdmi in and get 176k from SACDs.

I like the sound. 

Good luck.

I have a Sony UBP-X1100ES,  and I tried the hdmi marked audio out, into my McIntosh MDA200 dac hdmi input, and got nothing. I used a SACD which played fine using the coax.

I guess it's only for  input from a TV , but i don't see why it shouldn't work. 

One of the big issues with i2s is that they do not have standard pin protocol. If you do go with the dds route you need to make sure the pin out matches the pin in. Singer actually has pin toggles to match the dac i2s inputs of different dac. Guess  the main thing to know even though hdmi and i2s are the same cables they are not the same inputs or outputs.

No that connection is not compatible, but the DDC route would allow outputting I2S to your DAC....and it's a terrific connection. Unfortunately there is no I2S standard (I hope that will change), so that would be a phone call to the manufacturer unless you know your DAC is configurable

Thank you, all. I've decided to abandon my attempt to make my Sony unit into a transport. I have a server on order. I'll be able to step up my digital game when it arrives. Again, Thanks.