diff --git a/src/conf/ucm/codecs/rt5651/MonoSpeaker.conf b/src/conf/ucm/codecs/rt5651/MonoSpeaker.conf
index 0c3492fb..f4181d10 100644
--- a/src/conf/ucm/codecs/rt5651/MonoSpeaker.conf
+++ b/src/conf/ucm/codecs/rt5651/MonoSpeaker.conf
@@ -9,7 +9,21 @@ SectionDevice."MonoSpeaker" {
 	EnableSequence [
 		cdev "hw:bytcrrt5651"
 
-		# Map left and right input on left
+		# On most (all?) devices with a single / mono speaker an
+		# amplifier with a differential input connected between LOUT
+		# right and left is used. We deal with this by silencing the
+		# right output and mixing left + right to the left output.
+		#
+		# An alternative approach for devices using the differential
+		# setup would be to set bit 15 of register 5 in the codec,
+		# which turns the stereo unbalanced line out into a mono
+		# balanced line out.
+		#
+		# This possibility was discovered after we already shipped the
+		# current solution and the current solution has the advantage
+		# of also working on devices which only use LOUT left in
+		# unbalanced mode. The net result is the same for devices using
+		# the differential setup, so we just stick with what we have.
 		cset "name='Stereo DAC MIXR DAC R1 Switch' off"
 		cset "name='Stereo DAC MIXL DAC R1 Switch' on"