From: Mike Hodson <mystica_at_gmail.com>
Date: Thu, 13 Aug 2009 11:00:15 -0600

On Wed, Aug 12, 2009 at 11:20 AM, Salokyn<nicolas.gif_at_free.fr> wrote:
> Hi,
>
> Since some time (maybe 3.0) I got a loud white noise when play songs after
> having pushed stopped. This never happened before.
>
> My player is an iAudio X5 with RB r22166-090805. I found a similar problem
> on the forum here : http://forums.rockbox.org/index.php?topic=11216.0 (I
> can't log on the forum so I post here)

I have a Sansa E250 (as mentioned in your linked forum post) and have
noticed the problem you describe for a very long time. I did not
however notice it with an iRiver H320. In my case, It seems to be the
flash reading buffering the track which causes electrical noise on the
internal circuit board. I hear the slight noise every time I see the
flash chip access indicator in the upper right of my screen.

One thing I did notice recently however, is that with some new
headphones (rated at 105dB SPL _at_ 1mW mind you, so -very- sensitive)
the noise is noticeably louder -- likely due to the constant amplitude
of whatever pulses read the SD card, and the lower amplitude of the
audio signal required to generate the same amount of dB in my
headphones.

> Once the noise begins, it continues whatever I change tracks or stop/play,
> even if I skip tracks enough to force buffer to fill again.
> It happens after pushing stop and then open a track or resume the current
> one.

> It doesn't happen if I change track without pushing stop or when I just turn
> my player on (new trak or resume).

Due to how the buffer acts, it will fill to a set memory size, fitting
however many songs fit in said memory size into the memory. This
minimizes disk/flash reads and prolongs battery life as much as
possible, by not spinning the disk up any more than needed.

Your 'doesn't happen when i just turn my player on' report however
seems inconsistent with a 'buffering' operation... Are you saying that
once you turn the player on from a cold start, listening to the
headphones the entire time before music plays, you do not hear it at
all?

I would speculate that if you listened, from the moment you engaged
the power button at a total power off state, until the first disk read
had finished (to buffer the first and subsequent tracks) that there
would be *some* similar noise.

> To stop the noise, I must restart my player or reduce the sound level and
> rise it back as suggested on the forum post.

I believe the only thing lowering and raising the sound level is
doing, is allowing the disk to finish buffering to memory and then
spinning down... As for restarting, I am very hesitant to say that
'fixes' the problem, without a full test, headphones on, from startup
to the beginning of music playback.

If I am wrong in my guess as to what this is, please let us know!

Mike
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Received on 2009-08-13