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Topic: USB vs HDMI? (Read 3890 times) previous topic - next topic
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USB vs HDMI?

There's two parts to my question. What I'm basically trying to do is get a simple, (yet decent quality), port-to-line-level RCA out. I say "port" because my laptop has USB 3.1 (Gen 1 & 2), and HDMI ports. I'm using a Focusrite Scarlett 2i2 now, but I'd like to have something with a smaller footprint.  I want to test several headphone amps that I have, using the music on my laptop. (All are line level analog input.) 90% of listening will be with 320 CBR MP3's. Some wave files. No hi-res files.

I've seen some adaptors that appear to be only a cable. Especially in the HDMI-to-RCA class. So:

1. Is the digital signal that comes out HDMI the same one that comes out USB? In other words, the same quality and resolution? Does it matter which I use?

2. USB interfaces tend to be expensive, and include headphone amps, (which I don't need for this application), and other lights, bells, and whistles. I don't need coax, Toslink, SPDIF etc. Just port-to-RCA. Could one of those $20 - $30 HDMI-to-RCA convertors provide any decent quality?

Am I being unrealistic in thinking I could match, or come close to, the quality of my 2i2 with one of those small "cord" convertors?

Thanks all.

Re: USB vs HDMI?

Reply #1 –
I haven't paid attention but I have the impression that HDMI output uses it own version of lossy compression, which, if true, would mean your audio data would be converted before traveling through the output.

Re: USB vs HDMI?

Reply #2 –
I don't know about adapters, but HDMI protocol itself doesn't compress audio. It supports DSD, DTS and Dolby, but mostly it's LPCM...

Re: USB vs HDMI?

Reply #3 –
Quote from: Artie on
1. Is the digital signal that comes out HDMI the same one that comes out USB? In other words, the same quality and resolution? Does it matter which I use?
As long as you've configured both DACs for the same bit depth and sample rate, the digital signal will be the same.

Quote from: Artie on
2. USB interfaces tend to be expensive, and include headphone amps, (which I don't need for this application), and other lights, bells, and whistles. I don't need coax, Toslink, SPDIF etc. Just port-to-RCA. Could one of those $20 - $30 HDMI-to-RCA convertors provide any decent quality?
Good DACs don't have to be expensive, so it's entirely possible. I can't make any promises, though.

Quote from: AndyH-ha on
I haven't paid attention but I have the impression that HDMI output uses it own version of lossy compression, which, if true, would mean your audio data would be converted before traveling through the output.
HDMI supports uncompressed PCM, and an HDMI-to-RCA adapter almost certainly requires uncompressed PCM. A laptop would be configured to output PCM by default anyway. You have to do extra work to either re-encode the audio on-the-fly or pass it through without first decompressing it.

Re: USB vs HDMI?

Reply #4 –
Thanks all. I think I'll give one of those HDMI-to-RCA adaptors a try.

Re: USB vs HDMI?

Reply #5 –
Quote
USB interfaces tend to be expensive
Really?
There is a plethora of USB dongles out there costing approximately $10
This one I bought because my new phone lacks the headphone jack: https://www.amazon.com/UGREEN-3-5mm-Headphone-Adapter-Connector/dp/B08TR7LWQH/ref=sr_1_5?crid=15JL8DVDV6BC8&keywords=ugreen%2Bdac&qid=1684662032&sprefix=ugreen%2Bdac%2Caps%2C154&sr=8-5&th=1

https://www.audiosciencereview.com/forum/index.php?threads/review-apple-vs-google-usb-c-headphone-adapters.5541/
TheWellTemperedComputer.com

Re: USB vs HDMI?

Reply #6 –
Quote from: Roseval on
There is a plethora of USB dongles out there costing approximately $10.

Yeah, and I have a couple of them in that price range. Neither sounded very good, but, I only tried them with headphones. I didn't try them at line level. There's a good chance their "problem" was in driving headphones. I'll give them both another try as line drivers.

Re: USB vs HDMI?

Reply #7 –
Quote from: Artie on
Quote from: Roseval on
There is a plethora of USB dongles out there costing approximately $10.

Yeah, and I have a couple of them in that price range. Neither sounded very good, but, I only tried them with headphones. I didn't try them at line level. There's a good chance their "problem" was in driving headphones. I'll give them both another try as line drivers.

I've seen measurements of some of those cheap Apple USB-C adapters showing them driving low impedance headphones remarkably well.  If you don't need USB-A, might be worth looking into, although I suppose you might lose a few dB if you put them into a line level input.

Re: USB vs HDMI?

Reply #9 –
Quote from: saratoga on
I've seen measurements of some of those cheap Apple USB-C adapters showing them driving low impedance headphones remarkably well.

They do.
However the EU version is a bit anemic.
The USA version performs well: https://www.audiosciencereview.com/forum/index.php?threads/review-apple-vs-google-usb-c-headphone-adapters.5541/
TheWellTemperedComputer.com

Re: USB vs HDMI?

Reply #10 –
I think I'm going to forget about messing with HDMI. My impetus for thinking about it is that I usually have four USB ports on my laptop tied up with something else. I never use the HDMI port. But one of my USB uses is the Scarlett 2i2. If I go this other route, that will free that one up.

Re: USB vs HDMI?

Reply #12 –
Quote from: Artie on
My impetus for thinking about it is that I usually have four USB ports on my laptop tied up with something else.
External USB hub?
It's your privilege to disagree, but that doesn't make you right and me wrong.

Re: USB vs HDMI?

Reply #13 –
Quote from: fooball on
External USB hub?

No. My laptop has 4 USB 3.1, a USB C and an HDMI and something called a Dual Mode mini DisplayPort. It has a surprising amount of ports for a laptop.

(And a LAN port.)

Re: USB vs HDMI?

Reply #14 –
I was just suggesting that if you are running out of ports there is a fix.  I find it very convenient to have all my desk-based accessories (keyboard & mouse in particular) connected to a hub, and then it's just one cable to unplug/plug when the notebook goes mobile.
It's your privilege to disagree, but that doesn't make you right and me wrong.

Re: USB vs HDMI?

Reply #15 –
Running out of ports isn't really a problem. I just thought it might be interesting to utilize the HDMI port. Now that I'm retired, my laptop never goes mobile.   ;)

Re: USB vs HDMI?

Reply #16 –
Quote from: Artie on
Running out of ports isn't really a problem.
Oh, OK.  Pardon me for reading.

Quote from: Artie on
My impetus for thinking about it is that I usually have four USB ports on my laptop tied up with something else... If I go this other route, that will free that one up.
It's your privilege to disagree, but that doesn't make you right and me wrong.

Re: USB vs HDMI?

Reply #17 –
Quote from: fooball on
Oh, OK.  Pardon me for reading.

Quote from: Artie on
My impetus for thinking about it is that I usually have four USB ports on my laptop tied up with something else... If I go this other route, that will free that one up.

Sorry. Didn't mean to sound nasty. I failed to mention that if I unplug my 2i2, that frees up a port for whatever new audio route I try. But I was still curious if HDMI output the same digital signal as USB.

Re: USB vs HDMI?

Reply #18 –
HDMI is not meant for this. Most HDMI audio extractors are meant to connect to an external monitor/tv that doesn't have HDMI audio built-in, or doesn't have an option for external speakers. If you found an HDMI cable that only has RCA audio outputs I suppose that's possible but it will likely create a dummy monitor in your OS that might cause other unforeseen issues. HDMI is meant to be a video/audio output, I don't think it supports audio only.

There are any number of USB interfaces you can choose from, including ones that have an ordinary cable form factor: https://www.amazon.com/Type-C-Splitter-Theater-Amplifier-Speaker/dp/B0B3XJ45ZX

Re: USB vs HDMI?

Reply #19 –
Quote from: andy o on
HDMI is not meant for this. Most HDMI audio extractors are meant to connect to an external monitor/tv that doesn't have HDMI audio built-in, or doesn't have an option for external speakers. If you found an HDMI cable that only has RCA audio outputs I suppose that's possible but it will likely create a dummy monitor in your OS that might cause other unforeseen issues. HDMI is meant to be a video/audio output, I don't think it supports audio only.

I disagree; there's no reason this can't work and no reason not to use HDMI as an audio output if that suits the user.  All you do is ignore the video.  You might have to persuade the laptop that there is a monitor connected, and duplicate the desktop to the (non-existent) monitor, but then HDMI becomes available as an audio output device.  It is irrelevant that "HDMI is not meant for this" – so what?  All that matters is it's a digital output with an audio channel.

But yes, USB will be easier (and the OP has already decided that).
It's your privilege to disagree, but that doesn't make you right and me wrong.

Re: USB vs HDMI?

Reply #20 –
Quote from: fooball on
Quote from: andy o on
HDMI is not meant for this. Most HDMI audio extractors are meant to connect to an external monitor/tv that doesn't have HDMI audio built-in, or doesn't have an option for external speakers. If you found an HDMI cable that only has RCA audio outputs I suppose that's possible but it will likely create a dummy monitor in your OS that might cause other unforeseen issues. HDMI is meant to be a video/audio output, I don't think it supports audio only.

I disagree; there's no reason this can't work and no reason not to use HDMI as an audio output if that suits the user.  All you do is ignore the video.  You might have to persuade the laptop that there is a monitor connected, and duplicate the desktop to the (non-existent) monitor, but then HDMI becomes available as an audio output device.  It is irrelevant that "HDMI is not meant for this" – so what?  All that matters is it's a digital output with an audio channel.

But yes, USB will be easier (and the OP has already decided that).
I didn't say it can't work. It probably will, but It's an unnecessary complication. The USB hardware is ubiquitous, cheaper, fit-for-purpose and less prone to unforeseen consequences.

A multi monitor setup works fine most of the time, but in some cases it can cause some issues, like when you have your monitor calibrated, or when you use HDR, all of which can behave differently depending on the graphics card/driver. It's nice not to depend on other hardware and drivers for a function that can be done with a much simpler implementation. There are USB to stereo RCA interfaces that are just a cable.

From the OP's responses it didn't seem like they had it decided.