Mike Easter  wrote:
> bob prohaska wrote:
>> Has anybody noticed a material difference in audio quality between
>> the headphone jack and what comes out of the HDMI port?
>
>
https://raspberrypi.stackexchange.com/questions/47699/sound-output-of-the-raspb
erry-pi
>
> Someone suggested that if you want really good audio, to use a card for
> the GPIO header:
> https://elinux.org/index.php?title=RPi_Expansion_Boards#Sound

The GPIO header allows connection to the PCM audio output signals.
These are the digital signals used to generate the analogue audio at
the headphone jack using a DAC (apparantly a very cheap
implementation using PWM according to the Stack Exchange link).

A quick look on Wikipedia indicates that HDMI also carries PCM audio,
so in theory HDMI audio should be equally good as the audio from the
GPIO because they're actually the same data (ignoring optional
formats over HDMI which might be slightly better in some specific
respects than the PCM - no idea if the Pi supports any of those, or
how they're any better for that matter).

https://en.wikipedia.org/wiki/HDMI

USB sound cards probably use PCM as well, though I don't know if the
bitrate limits might be lower, and some apparantly introduce a
delay. As far as quality goes it's most likely to be the DAC that
really counts, and anything sold as an audio adapter should be better
than PWM unless it's a complete rip-off.

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