Schema

README.md

@@ -16,6 +16,20 @@ MAX98357A I2S 3W DAC Class D Amplifier Module
 
 ![](images/amp.png)
 
+
+SD / MODE
+
+This pin is used for shutdown mode but is also used for setting which channel is output. It's a little confusing but essentially:
+
+    If SD is connected to ground directly (voltage is under 0.16V) then the amp is shut down
+    If the voltage on SD is between 0.16V and 0.77V then the output is (Left + Right)/2, that is the stereo average. 
+    If the voltage on SD is between 0.77V and 1.4V then the output is just the Right channel
+    If the voltage on SD is higher than 1.4V then the output is the Left channel.
+
+This is compounded by an internal 100K pulldown resistor on SD so you need to use a pullup resistor on SD to balance out the 100K internal pulldown.
+
+For the breakout board, there's a 1Mohm resistor from SD to Vin which, when powering from 5V will give you the 'stereo average' output. If you want left or right channel only, or if you are powering from non-5V power, you may need to experiment with different resistors to get the desired voltage on SD
+
 ```
 26 -> DIN
 27 -> BCLK