manual: Document the DAC power mode setting

Make a note of the fact that the M3K DAC's high performance
setting is not necessarily the highest quality setting --
see forum post
https://forums.rockbox.org/index.php/topic,52917.msg249741.html#msg249741

Change-Id: If0196d2a224868aae10d61f66bac2e8c6843263f

1 files changed, 21 insertions, 0 deletions

diff --git a/manual/configure_rockbox/sound_settings.tex b/manual/configure_rockbox/sound_settings.tex
index d91ffec989..c618f33603 100644
--- a/manual/configure_rockbox/sound_settings.tex
+++ b/manual/configure_rockbox/sound_settings.tex
@@ -184,6 +184,27 @@ change to customise your listening experience.
   the effect of widening the stereo field. A value of 100\% will leave the
   stereo field unaltered.
 
+\opt{dac_power_mode}{
+  \opt{fiiom3k}{
+  \section{DAC Power Mode}
+  The power mode setting lets you choose between the high performance and
+  battery-saving modes of the DAC. Although battery saver mode is intended
+  to maximize your battery life, potentially at the expense of quality, in
+  some cases it may produce better quality audio than high performance mode.
+  If you want to get the best audio quality, you should experiment with both
+  settings to see which one is actually better.
+  }
+  \opt{shanlingq1}{
+  \section{DAC Output Level}
+  The output level setting selects between the DAC's high and low gain modes.
+  High gain consumes more power, but allows for increased volume and allows
+  the DAC to drive higher impedance headphones.
+
+  High gain corresponds to a 2.0V RMS (root-mean-square) output level, and
+  low gain to a 1.0V RMS level.
+  }
+}
+
 \opt{depth_3d}{
   \section{3D Enhancement}
   3D Enhancement increases the perceived separation between the left and right