Whine when playing video
#21
(12-04-2019, 10:32 AM)m42uko Wrote: Another day, another attempt. This time, I added the following circuit instead of L11:
[Image: pbp_capmult.png]
And while it does not solve the problem entirely, it significantly reduces the noise down to an acceptable level. There is enough space on the PBP to fit this circuit, but it's still three components for one. Yet, I don't really have any other idea at the moment. Well, apart from messing with the SMPS chip, but I don't feel like risking to fry the entire board when I only have one to play with.

It’s cool you have made progress.  I don’t have hardware in hand yet.  I haven’t seen any measurements of the frequency.    I think  could measure a put a high pass filter on sound output. Though your solution to try and smooth the ripple at the putative source is more elegant.
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#22
(12-04-2019, 10:01 PM)Samarium151 Wrote: It’s cool you have made progress.  I don’t have hardware in hand yet.  I haven’t seen any measurements of the frequency.    I think  could measure a put a high pass filter on sound output. Though your solution to try and smooth the ripple at the putative source is more elegant.

Here are some measurements taken on the supply rail of the PA / USB (on L11):

pa_act: 250 mV ripple @ ~1.5 kHz
pa_off: 250 mV ripple @ ~150 Hz
pa_act_lowest_brightness: 300 mV ripple @ ~1kHz
pa_off_lowest_brightness: 300 mV ripple @ ~160Hz

pa_act_usb_mouse: 300 mV ripple @ ~3kHz
pa_act_usb_stick: 300 mV ripple @ ~4.5kHz
pa_act_usb_raspi: 300 mV ripple @ ~5.5kHz


Here are the corresponding screenshots for some:
Spoiler:


Oof, that's actually quite bad. Especially considering the wide frequency range and the amplitude... And even during these measurements, the frequency was anything but stable. I guess we'll really have to take a look at the SMPS...

Does anybody have a datasheet for that one?
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#23
Oh, and as for the cause of the noise, my best guess would be that it's caused by either a really low quality DC-DC converter with a non-fixed switching frequency, or by a decent one running in severe underload, which causes it to skip many pulses, effectively reducing the switching frequency from say around 50 kHz to as low as 150 Hz.
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#24
Wow, that's an obvious sawtooth.  See if you can find where a pulse is going into an integrator.
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#25
Just as a quick update, I talked to Pine64's support about getting the datasheets for the DC-DC coverter and audio power amp IC, but they are sadly not able to provide them. Apart from that, I haven't looked into anything else since the last post.
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#26
(12-15-2019, 08:03 AM)m42uko Wrote: Just as a quick update, I talked to Pine64's support about getting the datasheets for the DC-DC coverter and audio power amp IC, but they are sadly not able to provide them. Apart from that, I haven't looked into anything else since the last post.

Still waiting on my hardware so I can’t try and reproduce yet.  The data you’ve gathered is pretty awesome.    I do wonder why your board doesn’t match the schematic.  Did pine support have any insight to that?
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#27
Just wanted to make a quick report that I also experience the whine with the PBP powered off and charging.
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#28
(11-09-2019, 06:35 AM)Firestorm Wrote: I confirm the whimpering sound.

Guys, this has nothing to do with CPU / GPU being under load. Run the famous gears simulation if in doubt. Or, playback audio without any video simply with a command line player.

I understand this is purely a sound issue. Whenever the software brings the sound system up for playback you can hear this noise. When the playback stops, the sound interface is turned off after 5sec or so to save energy (I guess).

My main concern is that this might be an actual hardware issue, if say the filters aren't designed right and voltage fluctuations speak over to the D/A converter. I hope some of the hardware developers will comment on this issue.

On thing is for sure: this is a REAL pain. Unless you are working in terribly loud environments this sound is really disturbing and makes listening to music particularly annoying since you have this constant whining sound also in quiet parts of songs.

EDIT: those concerned with whether your output is muted or not. Muting the sound means the volume (in the driver) is reduced to 0. This does not change the fact that the actual sound interface (D/A converters and such) are still powered up (which seems to produce the whining sound).

You seem to be fairly knowledgeable about this, my pbp has had a whine since I received it. It just kinda ramps up and down consistently. I don't use this thing for much video playback besides when i usb-c out to the tv. It didn't make any extra noise through the speakers, and if it does, I couldn't tell.

Basically, I'm not sure if I should be concerned. I didn't think anything of it because it was happening out of the box. But after seeing this thread, I might be a little more worried. I love this thing, I'm super new to linux and don't want it to shit out on me... Couldn't afford a different computer any time soon.

Thanks in advance!
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#29
Over time I have noticed the whine more often when the PBP is charging via barrel plug or USB-C. When I unplug either, the whine often goes away.

While charging, the whine lowers volume or ceases when I move the mouse, switch tabs in the web browser, or other activity. The whine returns to "full volume" when the activity ends.
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