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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?

128x128richardbrand
mike_in_nc
1,154 posts
 

Most computers have several USB ports, so one is likely to be available for digital audio output. On the other hand, not all computers have HDMI, and the ones I have seen have only one HDMI port, intended for the monitor. All that makes USB a useful input for a DAC.

Of course, some newer DACs are adding HDMI input.

richardbrand's avatar
richardbrand OP
186 posts
 

@mike_in_nc 

Yes, that makes sense for computers.  My partner's Dell XPS 13 has so little space for any physical connections, it has an external adapter to support HDMI and Ethernet over USB!

What about separate streaming boxes.  What would be the best connection to a DAC for them?

Do most people stream via computers these days?  The only streaming I use is to check the music out before buying a disk, and I use WiFi (great Australian invention) to connect my mobile to the pre-processor for that.

mike_in_nc
1,154 posts
 

The best connection is the one supported both by the streamer and by the DAC. Some manufacturers have their own connections (like Auralic’s Lightning Link) or use I2S, and many say that the sound is best if those are used. I have no experience with that.

Leaving aside specialty links, if USB is available, I like to use that, as it supports the widest range of sampling rates. Also, over USB, the DAC controls the clock entirely, without depending on the source. I will say, though, that with the new equipment I’ve tried recently, I cannot hear any difference between USB and SPDIF or AES3.

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