diff --git a/firmware/drivers/wm8975.c b/firmware/drivers/wm8975.c
index 89e0b155da..9052236131 100644
--- a/firmware/drivers/wm8975.c
+++ b/firmware/drivers/wm8975.c
@@ -53,7 +53,7 @@ int tenthdb2master(int db)
     /* 1111111 == +6dB  (0x7f) */
     /* 1111001 == 0dB   (0x79) */
     /* 0110000 == -73dB (0x30 */
-    /* 0101111 == mute  (0x2f) */
+    /* 0101111..0000000 == mute  (0x2f) */
 
     if (db < VOLUME_MIN) {
         return 0x0;
@@ -65,14 +65,8 @@ int tenthdb2master(int db)
 /* convert tenth of dB volume (-780..0) to mixer volume register value */
 int tenthdb2mixer(int db)
 {
-    if (db < -660)                 /* 1.5 dB steps */
-        return (2640 - db) / 15;
-    else if (db < -600)            /* 0.75 dB steps */
-        return (990 - db) * 2 / 15;
-    else if (db < -460)            /* 0.5 dB steps */
-        return (460 - db) / 5; 
-    else                           /* 0.25 dB steps */
-        return -db * 2 / 5;
+    (void)db;
+    return 0;
 }
 
 
@@ -171,25 +165,28 @@ int audiohw_set_mixer_vol(int channel1, int channel2)
     return 0;
 }
 
-/* We are using Linear bass control */
 void audiohw_set_bass(int value)
 {
-  int regvalues[]={11, 10, 10,  9,  8,  8, 0xf , 6, 6, 5, 4, 4, 3, 2, 1, 0};
+    const int regvalues[] = {
+        11, 10, 10, 9, 8, 8, 0xf, 6, 6, 5, 4, 4, 3, 2, 1, 0
+    };
 
-  if ((value >= -6) && (value <= 9)) {
-      /* We use linear bass control with 130Hz cutoff */
-      wmcodec_write(BASSCTRL, regvalues[value+6]);
-  }
+    if ((value >= -6) && (value <= 9)) {
+        /* We use linear bass control with 200 Hz cutoff */
+        wmcodec_write(BASSCTRL, regvalues[value + 6] | 0x40);
+    }
 }
 
 void audiohw_set_treble(int value)
 {
-  int regvalues[]={11, 10, 10,  9,  8,  8, 0xf , 6, 6, 5, 4, 4, 3, 2, 1, 0};
+    const int regvalues[] = {
+        11, 10, 10, 9, 8, 8, 0xf, 6, 6, 5, 4, 4, 3, 2, 1, 0
+    };
 
-  if ((value >= -6) && (value <= 9)) {
-      /* We use a 8Khz cutoff */
-      wmcodec_write(TREBCTRL, regvalues[value+6]);
-  }
+    if ((value >= -6) && (value <= 9)) {
+        /* We use linear treble control with 4 kHz cutoff */
+        wmcodec_write(TREBCTRL, regvalues[value + 6] | 0x40);
+    }
 }
 
 int audiohw_mute(int mute)
diff --git a/firmware/sound.c b/firmware/sound.c
index 01d76a0a39..6182e6b567 100644
--- a/firmware/sound.c
+++ b/firmware/sound.c
@@ -312,9 +312,14 @@ int current_bass = 0;      /* -150..+150     0..+240 */
 
 static void set_prescaled_volume(void)
 {
-    int prescale;
+    int prescale = 0;
     int l, r;
 
+/* The WM codecs listed don't have suitable prescaler functionality, so we let
+ * the prescaler stay at 0 for these unless SW tone controls are in use */
+#if defined(HAVE_SW_TONE_CONTROLS) || !(defined(HAVE_WM8975) \
+    || defined(HAVE_WM8731) || defined(HAVE_WM8721) || defined(HAVE_WM8751))
+
     prescale = MAX(current_bass, current_treble);
     if (prescale < 0)
         prescale = 0;  /* no need to prescale if we don't boost
@@ -325,13 +330,13 @@ static void set_prescaled_volume(void)
      * instead (might cause clipping). */
     if (current_volume + prescale > VOLUME_MAX)
         prescale = VOLUME_MAX - current_volume;
-   
+#endif
+
 #if defined(HAVE_SW_TONE_CONTROLS)
     dsp_callback(DSP_CALLBACK_SET_PRESCALE, prescale);
 #elif CONFIG_CODEC == MAS3507D
     mas_writereg(MAS_REG_KPRESCALE, prescale_table[prescale/10]);
-#elif defined(HAVE_UDA1380) || defined(HAVE_WM8975) || defined(HAVE_WM8758) \
-   || defined(HAVE_WM8731) || defined(HAVE_WM8721) || defined(HAVE_WM8751)
+#elif defined(HAVE_UDA1380) || defined(HAVE_WM8758)
     audiohw_set_mixer_vol(tenthdb2mixer(-prescale), tenthdb2mixer(-prescale));
 #endif