On 23/08/2019 05:08, A. Dumas 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?
>>
>> 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?
>
> 1. It's NOT a headphone plug because the output level is too low for
> headphones. It's a "3.5 mm line output". You would need a headphone
> amplifier.
> 2. The Pi has no audio chip (DAC). It uses a simple(*) filter circuit
> controlled by PWM. Sort of a manual 1-bit digital to analogue conversion by
> the CPU.
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


> 3. The analogue out sounds horrible. But, they improved the circuitry for
> the Pi3 and greatly improved the driver at some point. With that, it sounds
> pretty good. I don't know if the improved driver is now standard, I guess
> it might by. To be sure, add "audio_pwm_mode=2" to /boot/config.txt
> 4. HDMI output is digital. Quality of the sound on that end depends on
> where you plug it in.
> 5. You might (I do) still get some noise/hiss/beep even when using the
> hdmi. Annoying when quiet, not noticeable by me even at low music level, so
> I put up with it. Not sure of the source. Maybe the whole setup is not
> grounded well, maybe the power adapter of the Pi sucks, maybe the lcd
> display+control board I plugged on top adds noise.
> 6. I get perfect quality from a Pi Zero with IQaudIO DACzero board and a
> good old cinch cable.

I used a HifiBerry DAC board. Its pretty good

>
> * Relatively simple. Discussion:
>
https://hackaday.com/2018/07/13/behind-the-pin-how-the-raspberry-pi-gets-its-au
dio/
>


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kind word alone.

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