MacBook Pro output to DAC

So if I use a USB-C to HDMI cable from my MBPro into a DAC with the I2S connection, then I should be using the I2S signal into the DAC right or is it more complicated than that?

A low-jitter USB converter will easily beat the Toslink output from the Mac. The best way to go is I2S, but your DAC must have this input. Next to that, S/PDIF coax will be great. Whatever cable you end-up with, it should be a high quality cable. Makes a big difference. Cables in the $100-300 range will not get you there.

Firewire is no better than USB. It all depends on the implementation/design. Either can be great.

Steve N.
Empirical Audio

I use the optical output as explained above with better results than USB. I believe you also have a firewire connection? but you would need an interface to make the connection if your DAC does not have a firewire port. Firewire is best used as a direct connection say to a weiss dac. It is far superior than the other two options

Depends on your DAC. If it has a good USB input, that would be the way to go. If not, USB to spdif converter into your DAC would be next best probably, followed by min-toslink into DAC.

I think the headphone out is also an optical out on the Macbook Pro. If that's correct and your DAC has an optical input, then all you need is a mini-toslink to toslink cable (or an adapter and a toslink cable).