I don't have much invested in my digital front end, I'm mainly a vinyl guy, but the I2s connection made a noticeable improvement in performance using a DDC from a player via usb and outputting I2s into the DAC. The player has an I2s output as well, but is not user configurable, like some now are for different pin-outs. (neither is the DAC for that matter, but the DDC has limited options with potentially more to come via field programmable chip). My biggest gripe is, for audio, there is no standard but it seems that different manufacturers are falling into different categories; when I first employed such a set up, it was impossible to find a cable maker willing to custom build a suitable cable. Currently, I'm able to use the DH Labs one, which is modestly priced (and I believe, offhand, is an HDMI 2.1 protocol for what that's worth). Short runs are apparently essential.
Why does USB feature so much in discussions about DACs when the newer HDMI seems better?
I am a bit confused about the frequent mention of USB in the context of stand-alone Digital to Analog Converters (DAC). Why is HDMI left out? Is this a US versus Europe / Asia thing?
The Universal Serial Bus (USB) was introduced in 1996 by a group of computer manufacturers primarily to support plug-and-play for peripherals like keyboards and printers. It has only two signal wires, plus two wires that can supply DC power.
The High-Definition Multimedia Interface (HDMI) was specifically designed by a group of television manufacturers for transmitting digital audio and video in many formats. It hit the shops around 2004. There are 19 pins supporting four shielded twisted pairs, and seven other wires (3 of which can instead form a shielded twisted pair for Ethernet).
I have three universal disk players from Sony, Panasonic and Reavon, which all have two HDMI outputs, one can be dedicated to audio only, the other carries video or video plus audio. (Only the Panasonic does not support SACD). My Marantz AV 8802 pre-processor has 11 HDMI connections and only two USBs.
Of course, both USB and HDMI continue to evolve. Then there is the Media-Oriented System Transport (MOST) bus designed by the automotive industry, which looks even better.
Why is it so?