the BIAS register set to 0x200 on fake boot.

desmume/src/NDSSystem.cpp

@@ -2394,7 +2394,7 @@ void NDS_Reset()
 	memcpy(FW_Mac, (MMU.fw.data + 0x36), 6);
 
 	SPU_DeInit();
-	SPU_ReInit();
+	SPU_ReInit(!canBootFromFirmware && bootResult);
 
 	//this needs to happen last, pretty much, since it establishes the correct scheduling state based on all of the above initialization
 	initSchedule();

desmume/src/SPU.cpp

@@ -184,9 +184,13 @@ SoundInterface_struct *SPU_SoundCore()
 	return SNDCore;
 }
 
-void SPU_ReInit()
+void SPU_ReInit(bool fakeBoot)
 {
 	SPU_Init(SNDCoreId, buffersize);
+
+	// Firmware set BIAS to 0x200
+	if (fakeBoot)
+		SPU_WriteWord(0x04000504, 0x0200);
 }
 
 int SPU_Init(int coreid, int buffersize)

desmume/src/SPU.h

@@ -194,7 +194,7 @@ public:
 int SPU_ChangeSoundCore(int coreid, int buffersize);
 SoundInterface_struct *SPU_SoundCore();
 
-void SPU_ReInit();
+void SPU_ReInit(bool fakeBoot = false);
 int SPU_Init(int coreid, int buffersize);
 void SPU_Pause(int pause);
 void SPU_SetVolume(int volume);