Rockbox General > Rockbox General Discussion
Completely disable power management
saratoga:
--- Quote from: palik4 on October 01, 2019, 05:49:30 PM ---However, first I'll see if the solution for the mentioned SD card freeze issue solves my problem, as I have found your patch from June 2017 on CVDD2 voltage increase for SD cards. I took that and cherry-picked on top of the v3.14 branch, then created a custom 3.14 build for further testing during normal operation. It works so far without issues. We'll see how it goes for a week.
--- End quote ---
I didn't catch that you were running 3.14 and not the current build. If that patch helps, just update and you'll have those changes.
--- Quote from: palik4 on October 01, 2019, 05:49:30 PM ---By the way, regarding power management, is there any chance of Rockbox PM distorting audio at specific volume ranges? How is the voltage of the end amplifier (that generates the output for headphones) linked to CPU voltage/frequency?
--- End quote ---
Yes. There is a seperate power rail for the audio system. The voltage is set so that the player will distort above 0dB.
palik4:
--- Quote ---If that patch helps, just update and you'll have those changes.
--- End quote ---
Yes, I know but my intention was to keep the stable build if possible and have the fix only for things that really need to be fixed. I could verify the patch has become effective as CVVD2 is now between 2750-2765 under Debug -> View I/O Ports.
--- Quote ---Yes. There is a seperate power rail for the audio system. The voltage is set so that the player will distort above 0dB.
--- End quote ---
Good to know. I also noticed that above 3 dB the volume doesn't change immediately but with a 2 second delay. Is this some kind of software volume overdrive that takes place in the audio buffer?
I've also read in a previous thread that voltage for the audio system is lowered for power management purposes if I stay at lower volume levels. I can hear pops & crackles when adjusting the volume between -43 and -44 dB, -9 and -8 dB, -3 and -2 dB, 1 and 2 dB. These are hardly noticeable during playback but indicate that something changes underneath. Are these voltage levels safe for all kinds of audio equipment used for listening, and should not distort at any levels below 0 dB, regardless the impedance of connected headphones or amplifier?
saratoga:
--- Quote from: palik4 on October 02, 2019, 02:14:33 AM ---
--- Quote ---If that patch helps, just update and you'll have those changes.
--- End quote ---
Yes, I know but my intention was to keep the stable build if possible and have the fix only for things that really need to be fixed.
--- End quote ---
As you have noticed, old builds tend to be less stable than newer ones, so I do not recommend doing this.
--- Quote from: palik4 on October 02, 2019, 02:14:33 AM ---Good to know. I also noticed that above 3 dB the volume doesn't change immediately but with a 2 second delay. Is this some kind of software volume overdrive that takes place in the audio buffer?
--- End quote ---
We don't do software volume control, and there should not be any delay.
--- Quote from: palik4 on October 02, 2019, 02:14:33 AM ---I've also read in a previous thread that voltage for the audio system is lowered for power management purposes if I stay at lower volume levels.
--- End quote ---
I don't think we do anything like that, although I could be forgetting.
--- Quote from: palik4 on October 02, 2019, 02:14:33 AM --- I can hear pops & crackles when adjusting the volume between -43 and -44 dB, -9 and -8 dB, -3 and -2 dB, 1 and 2 dB. These are hardly noticeable during playback but indicate that something changes underneath.
--- End quote ---
That was a side effect of one of the more recent changes, I think this one: https://github.com/Rockbox/rockbox/commit/42219b6e797791e2c037c41393a87513973e4588
These voltage levels are within spec. I think the minimum impedance without distortion is around 8-10 ohms, that is a hardware thing that cannot be changed and does not depend on voltage.
palik4:
--- Quote ---As you have noticed, old builds tend to be less stable than newer ones, so I do not recommend doing this.
--- End quote ---
I'm not really a fan of rolling releases. :-\ They always tend to have more bugs and instability by definition, as new features always come with new bugs. Also, I don't like changes of behavior, even small ones, like extra or removed menu entries, extra features I don't need. The real problem here is that your stable branch doesn't get updated with bugfixes. If it did, it would be more stable than your development builds by definition. In the future it would be nice to have a real maintenance release (like a 3.14.1), with bugfixes only against a stable branch (now 3.14). 8) However, if your CVVD2 patch doesn't help on the SD card freeze problem, I will give the devlopment build a try for daily usage. ;)
--- Quote ---We don't do software volume control, and there should not be any delay.
--- End quote ---
If you raise the volume from 2 to 3-6 dB, there is definitely a 2 second delay before the audible amplification takes place. Below 2 dB the audible volume is changed immediately. This effect just reminded me to software volume overdrive which players do in their buffer so it would take a few moments to the not-yet amplified buffer data to be read and played.
--- Quote ---These voltage levels are within spec. I think the minimum impedance without distortion is around 8-10 ohms, that is a hardware thing that cannot be changed and does not depend on voltage.
--- End quote ---
That is good to know. Thanks for clarifying.
johnb:
On the AMS Sansas, the volume step is 1.5dB.
I.e. you have to click twice to really hear a change (otherwise it is rounded).
See
http://gerrit.rockbox.org/r/#/c/1555/
Is this what you experience?
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