diff --git a/firmware/target/arm/imx233/audioout-imx233.c b/firmware/target/arm/imx233/audioout-imx233.c
index e5e1e37264..e9b368c9b6 100644
--- a/firmware/target/arm/imx233/audioout-imx233.c
+++ b/firmware/target/arm/imx233/audioout-imx233.c
@@ -53,6 +53,13 @@ void imx233_audioout_preinit(void)
     __REG_CLR(HW_AUDIOOUT_PWRDN) = HW_AUDIOOUT_PWRDN__HEADPHONE;
     /* Set HP mode to AB */
     __REG_SET(HW_AUDIOOUT_ANACTRL) = HW_AUDIOOUT_ANACTRL__HP_CLASSAB;
+    /* change biais to -50% */
+    __REG_CLR(HW_AUDIOOUT_TEST) = HW_AUDIOOUT_TEST__HP_I1_ADJ_BM;
+    __REG_SET(HW_AUDIOOUT_TEST) = HW_AUDIOOUT_TEST__HP_I1_ADJ_M_50;
+    __REG_CLR(HW_AUDIOOUT_REFCTRL) = HW_AUDIOOUT_REFCTRL__BIAS_CTRL_BM;
+    __REG_SET(HW_AUDIOOUT_REFCTRL) = 1 << HW_AUDIOOUT_REFCTRL__BIAS_CTRL_BP;
+    __REG_SET(HW_AUDIOOUT_REFCTRL) = HW_AUDIOOUT_REFCTRL__RAISE_REF;
+    __REG_SET(HW_AUDIOOUT_REFCTRL) = HW_AUDIOOUT_REFCTRL__XTAL_BGR_BIAS;
     /* Stop holding to ground */
     __REG_CLR(HW_AUDIOOUT_ANACTRL) = HW_AUDIOOUT_ANACTRL__HP_HOLD_GND;
     /* Set dmawait count to 31 (see errata, workaround random stop) */
diff --git a/firmware/target/arm/imx233/audioout-imx233.h b/firmware/target/arm/imx233/audioout-imx233.h
index acfb56138f..fbc0827be2 100644
--- a/firmware/target/arm/imx233/audioout-imx233.h
+++ b/firmware/target/arm/imx233/audioout-imx233.h
@@ -86,7 +86,13 @@
 #define HW_AUDIOOUT_PWRDN__SPEAKER          (1 << 24)
 
 #define HW_AUDIOOUT_REFCTRL     (*(volatile uint32_t *)(HW_AUDIOOUT_BASE + 0x80))
-#define HW_AUDIOOUT_REFCTRL__LOW_PWR    (1 << 19)
+#define HW_AUDIOOUT_REFCTRL__BIAS_CTRL_BP   16
+#define HW_AUDIOOUT_REFCTRL__BIAS_CTRL_BM   (3 << 16)
+#define HW_AUDIOOUT_REFCTRL__LOW_PWR        (1 << 19)
+#define HW_AUDIOOUT_REFCTRL__VBG_ADJ_BP     20
+#define HW_AUDIOOUT_REFCTRL__VBG_ADJ_BM     (3 << 20)
+#define HW_AUDIOOUT_REFCTRL__XTAL_BGR_BIAS  (1 << 24)
+#define HW_AUDIOOUT_REFCTRL__RAISE_REF      (1 << 25)
 
 #define HW_AUDIOOUT_ANACTRL     (*(volatile uint32_t *)(HW_AUDIOOUT_BASE + 0x90))
 #define HW_AUDIOOUT_ANACTRL__HP_CLASSAB         (1 << 4)
@@ -98,6 +104,14 @@
 #define HW_AUDIOOUT_ANACTRL__SHORT_LR_STS       (1 << 24)
 #define HW_AUDIOOUT_ANACTRL__SHORT_CM_STS       (1 << 28)
 
+#define HW_AUDIOOUT_TEST        (*(volatile uint32_t *)(HW_AUDIOOUT_BASE + 0xa0))
+#define HW_AUDIOOUT_TEST__HP_I1_ADJ_BM      (3 << 22)
+#define HW_AUDIOOUT_TEST__HP_I1_ADJ_BP      22
+#define HW_AUDIOOUT_TEST__HP_I1_ADJ_NOMINAL (0 << 22)
+#define HW_AUDIOOUT_TEST__HP_I1_ADJ_M_50    (1 << 22)
+#define HW_AUDIOOUT_TEST__HP_I1_ADJ_P_100   (2 << 22)
+#define HW_AUDIOOUT_TEST__HP_I1_ADJ_P_50    (3 << 22)
+
 #define HW_AUDIOOUT_ANACLKCTRL  (*(volatile uint32_t *)(HW_AUDIOOUT_BASE + 0xe0))
 #define HW_AUDIOOUT_ANACLKCTRL__DACDIV_BP   0
 #define HW_AUDIOOUT_ANACLKCTRL__DACDIV_BM   (7 << 0)