diff --git a/lib_xua/src/core/audiohub/xua_audiohub.xc b/lib_xua/src/core/audiohub/xua_audiohub.xc
index 885fe521..3089523a 100755
--- a/lib_xua/src/core/audiohub/xua_audiohub.xc
+++ b/lib_xua/src/core/audiohub/xua_audiohub.xc
@@ -805,6 +805,9 @@ void XUA_AudioHub(chanend ?c_aud, clock ?clk_audio_mclk, clock ?clk_audio_bclk,
             /* Notify clockgen of new mCLk */
             c_mclk_change <: mClk;
             c_mclk_change <: curFreq;
+
+            /* Wait for ACK back from clockgen to signal clocks all good */
+            c_mclk_change :> int _;
 #endif
         }
 
diff --git a/lib_xua/src/core/clocking/clockgen.xc b/lib_xua/src/core/clocking/clockgen.xc
index b22dd906..b3fd4c18 100644
--- a/lib_xua/src/core/clocking/clockgen.xc
+++ b/lib_xua/src/core/clocking/clockgen.xc
@@ -347,6 +347,8 @@ void clockGen ( streaming chanend ?c_spdif_rx,
 #if (USE_SW_PLL && (XUA_SPDIF_RX_EN || XUA_ADAT_RX_EN))
     chan c_sigma_delta;
     int reset_sw_pll_pfd = 1;
+    int require_ack_to_audio = 0;
+    
     unsafe {
         selected_mclk_rate_ptr = &selected_mclk_rate;
     }
@@ -531,6 +533,17 @@ void clockGen ( streaming chanend ?c_spdif_rx,
                     break;
 #endif
 
+#if ((XUA_SPDIF_RX_EN || XUA_ADAT_RX_EN) && USE_SW_PLL)
+                case inuint_byref(c_sigma_delta, tmp): 
+                    printstr("ACK\n");
+                    if(require_ack_to_audio)
+                    {
+                        c_mclk_change <: tmp;
+                        require_ack_to_audio = 0;
+                    }
+                    break;
+#endif
+
 #if (XUA_SPDIF_RX_EN || XUA_ADAT_RX_EN)
                 case c_mclk_change :> selected_mclk_rate:
                     c_mclk_change :> selected_sample_rate;
@@ -539,6 +552,7 @@ void clockGen ( streaming chanend ?c_spdif_rx,
                     mclks_per_sample = selected_mclk_rate / selected_sample_rate;
                     restart_sigma_delta(c_sigma_delta);
                     reset_sw_pll_pfd = 1;
+                    require_ack_to_audio = 1;
 #endif
                     break;
 #endif
diff --git a/lib_xua/src/core/clocking/sw_pll_wrapper.xc b/lib_xua/src/core/clocking/sw_pll_wrapper.xc
index 664fa5c2..64fbfdec 100644
--- a/lib_xua/src/core/clocking/sw_pll_wrapper.xc
+++ b/lib_xua/src/core/clocking/sw_pll_wrapper.xc
@@ -137,7 +137,9 @@ void SigmaDeltaTask(chanend c_sigma_delta, unsigned * unsafe selected_mclk_rate_
     tmr :> time_trigger;
     int running = 1;
 
-    unsigned rx_word;
+    outuint(c_sigma_delta, 0); /* Signal back via clockgen to audio to start I2S */
+
+    unsigned rx_word = 0;
     while(running)
     {
         /* Poll for new SDM control value */
@@ -146,7 +148,6 @@ void SigmaDeltaTask(chanend c_sigma_delta, unsigned * unsafe selected_mclk_rate_
             case inuint_byref(c_sigma_delta, rx_word):
                 if(rx_word == DISABLE_SDM)
                 {
-                    printhexln(rx_word);
                     f_error = 0;
                     running = 0;
                 }