Has anybody noticed a material difference in audio quality between the headphone jack and what comes out of the HDMI port?
Obviously, a display with a poor audio circuit can corrupt a good signal, but assuming the display is "good enough" does it matter which is used?
Thanks for reading,
bob prohaska
It has been discussed such as here
(that also has a number of useful links)
The problem is the limitations of how RPi generates the analog audio -- 'tacky' for an audiophile.
Someone suggested that if you want really good audio, to use a card for the GPIO header:
RPi Expansion Boards
2.10 Sound 2.10.1 Audio Injector zero sound card 2.10.2 Audio Injector stereo sound card 2.10.3 Audio Injector Octo sound card 2.10.4 Wolfson sound card 2.10.5 HiFiBerry DAC 2.10.6 HiFiBerry Digi 2.10.7 Raspi-T-DAC 2.10.8 Pisound-- Mike Easter
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).
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.
-- __ __ #_ < |\| |< _#
When I started to employ my 3B RPi using some leftover parts, I had a VGA monitor and USB kb & mouse, so I needed an HDMI to VGA adapter. There were places that had adapters w/ a 3.5mm for audio, but I opted for an adapter w/o audio plug outlet in favor of just using the RPi's audio outs for some little 'computer speakers'.
But, I'm puzzled about the analog vs digital. I would assume that the HDMI audio is digital, but the 3.5mm plug sounds/looks like an analog audio outlet.
But, I'm sure those HDMI to VGA adapters w/ audio plug aren't converting digital to analog audio. What is the answer to my confusion?
-- Mike Easter
IIUC, the transition from digital to analog audio then occurs in the monitor, if using the HDMI connection, or the Pi itself, if using the headphone jack. Have I got this much right?
I've tried using the audio output on a Dell ST2200L HDMI monitor and the headphone jack, neither showed any obvious defects.
Thanks to all for reading and posting informative links.....
bob prohaska test
I havent tried but I can assure you that cheap amps to drive headphones will be of low quality. And the DACs in pis are cheap and nastry tech too.
The HDMI should be pure digital and of far higher quality
If you want quality *analogue* audio, get a decent DAC.
-- ?The ultimate result of shielding men from the effects of folly is to fill the world with fools.? Herbert Spencer
Why not? To do it rather badly is not that hard
-- If you tell a lie big enough and keep repeating it, people will eventually come to believe it. The lie can be maintained only for such time as the State can shield the people from the political, economic and/or military consequences of the lie. It thus becomes vitally important for the State to use all of its powers to repress dissent, for the truth is the mortal enemy of the lie, and thus by extension, the truth is the greatest enemy of the State.
Joseph Goebbels
No, the defects are subtle. But they are there
-- If you tell a lie big enough and keep repeating it, people will eventually come to believe it. The lie can be maintained only for such time as the State can shield the people from the political, economic and/or military consequences of the lie. It thus becomes vitally important for the State to use all of its powers to repress dissent, for the truth is the mortal enemy of the lie, and thus by extension, the truth is the greatest enemy of the State.
Joseph Goebbels
Almost delata modulation! :-)
Actually 1 bit DAC PWN can be amongst the lowest distortion and highest quality ... the errors are down to timing issues rather than voltage issues as it were.
But you should be clocking pretty fast. and that makes timing harder
I used a HifiBerry DAC board. Its pretty good
-- You can get much farther with a kind word and a gun than you can with a kind word alone. Al Capone
There are some surprisingly good (not great) op-amp based ones (Cmoy derivatives) that aren't too expensive especially as kits.
That they are.
Depending on the DAC it meets.
Or start analogue and keep it that way which is *much* more expensive and doesn't work when a computer is involved.
-- Steve O'Hara-Smith | Directable Mirror Arrays C:\>WIN | A better way to focus the sun The computer obeys and wins. | licences available see You lose and Bill collects. | http://www.sohara.org/
ng
Just got a cheap HDMI to VGA adapter with audio from CPC:
AV27363 - UNBRANDED 77HDMIVGCBL033 HDMI to VGA Lead with Audio, Gold
As HDMI has no analog audio it must be converting the HDMI digital audio stream to stereo analog on its 3.5 mm jack plug. Not sure if it or omxplayer on a Raspberry Pi is doing a basic 5.1 or 7.1 mix down to stereo. All I know is that if I play a channel check video file with only a 5.1 or 7.1 sound track I do hear all the channels on the correct side (and center) and at various levels. Except the .1 (LFE) which is to be expected.
Quality is pretty good, the level might be a bit on the high side.
-- Cheers Dave.
Op 23-08-19 om 10:43 schreef Ahem A Rivet's Shot:
It does not have an audio DAC chip, or any DAC or ADC chip. Audio circuit schematic for the Pi4 at the bottom centre here:
It still has a DAC though
Even if its a couple of PWM outputs from te Pi main chip
Audio
Where is the rest of the schematic? What drives PWM1_MOS1 and 2?
-- "What do you think about Gay Marriage?" "I don't." "Don't what?" "Think about Gay Marriage."
Mostly proprietary SoC, Broadcom ARM version with their VideoCore GPU. I have no idea what's in there, but the Pi doesn't have hardware PWM or analogue gpio pins.
On Fri, 23 Aug 2019 10:06:41 +0100 (BST), "Dave Liquorice" declaimed the following:
But one should still need an amplifier for the audio output as that is most likely (consumer) line-level.
-- Wulfraed Dennis Lee Bieber AF6VN wlfraed@ix.netcom.com http://wlfraed.microdiversity.freeddns.org/
But that is a $67 box. The adapters I saw w/ or w/o audio out were comparable in price; $10 w/o audio
$13 w/ audio
The $13 Walmart w/ audio also comes w/: Audio Output: 3.5mm stereo jack with included stereo cable (6')
When I refer to 'little computer speakers' they are powered and line out (like RPi), not headphone jacked.
-- Mike Easter
So its a 1 bit per channel software DAC
-- "I am inclined to tell the truth and dislike people who lie consistently. This makes me unfit for the company of people of a Left persuasion, and all women"
Yes. That's why I said "audio DAC chip" in an effort to be more precise. Obviously there is always Digital to Analog Conversion but in the context of computer audio output circuitry, how I think most people understand it, the Pi does not have "a DAC".
Anyway, with that new driver the output seems to be entirely acceptable.
I am a software and a hardware engineer and I don't care whether its done in hardware of software, its a DAC,
You don?t need 'a chip' to do a DAC. I was setting up resistor based DACS before you were born, probably :-)
As I said, the issue is timing jitter mainly
And one man's 'acceptable' is another persons 'distortion'
-- ?when things get difficult you just have to lie?
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