diff --git a/examples/app_xua_simple/src/app_xua_simple.xc b/examples/app_xua_simple/src/app_xua_simple.xc
index 397c0d99..43deab2a 100644
--- a/examples/app_xua_simple/src/app_xua_simple.xc
+++ b/examples/app_xua_simple/src/app_xua_simple.xc
@@ -49,9 +49,6 @@ int main()
     /* Channel for communcating control messages from EP0 to the rest of the device (via the buffering cores */
     chan c_aud_ctl;
 
-    /* TODO handle this */
-    interface audManage_if i_audMan;
-
     par
     {
         /* Low level USB device layer core */ 
@@ -70,7 +67,7 @@ int main()
         on tile[1]: XUA_Buffer(c_ep_out[1], c_ep_in[1], c_sof, c_aud_ctl, p_for_mclk_count, c_aud);
 
         /* IOHub core does most of the audio IO i.e. I2S (also serves as a hub for all audio) */
-        on tile[0]: XUA_AudioHub(c_aud, i_audMan);
+        on tile[0]: XUA_AudioHub(c_aud, null);
     }
     
     return 0;
diff --git a/lib_xua/api/xua_audiohub.h b/lib_xua/api/xua_audiohub.h
index a9791115..0f1a9ef0 100644
--- a/lib_xua/api/xua_audiohub.h
+++ b/lib_xua/api/xua_audiohub.h
@@ -24,19 +24,19 @@ typedef interface audManage_if
  *  This function drives I2S ports and handles samples to/from other digital
  *  I/O threads.
  *
- *  \param c_in Audio sample channel connected to the mixer() thread or the
+ *  \param c_aud Audio sample channel connected to the mixer() thread or the
  *              decouple() thread
  *  \param c_dig channel connected to the clockGen() thread for
  *               receiving/transmitting samples
  *  \param c_config An optional channel that will be passed on to the
  *                  CODEC configuration functions.
  */
-void XUA_AudioHub(chanend ?c_in
+void XUA_AudioHub(chanend ?c_aud
 #if defined(SPDIF_TX) && (SPDIF_TX_TILE != AUDIO_IO_TILE)
-    chanend c_spdif_tx,
+    , chanend c_spdif_tx
 #endif
 #if(defined(SPDIF_RX) || defined(ADAT_RX))
-    chanend c_dig,
+    , chanend c_dig
 #endif
 #if (XUD_TILE != 0) && (AUDIO_IO_TILE == 0) && (XUA_DFU_EN == 1)
    , server interface i_dfu ?dfuInterface
@@ -44,7 +44,7 @@ void XUA_AudioHub(chanend ?c_in
 #if (NUM_PDM_MICS > 0)
     , chanend c_pdm_in
 #endif
-    , client audManage_if i_audMan
+    , client audManage_if ?i_audMan
 );
 
 void SpdifTxWrapper(chanend c_spdif_tx);
@@ -52,9 +52,11 @@ void SpdifTxWrapper(chanend c_spdif_tx);
 /* These functions must be implemented for the CODEC/ADC/DAC arrangement of a specific design */
 
 /* Any required clocking and CODEC initialisation - run once at start up */
+/* TODO Provide default implementation of this */
 void AudioHwInit();
 
 /* Configure audio hardware (clocking, CODECs etc) for a specific mClk/Sample frquency - run on every sample frequency change */
+/* TODO Provide default implementation of this */
 void AudioHwConfig(unsigned samFreq, unsigned mClk, unsigned dsdMode,
         unsigned sampRes_DAC, unsigned sampRes_ADC);
 
diff --git a/lib_xua/src/usb_audio/audiohub/xua_audiohub.xc b/lib_xua/src/usb_audio/audiohub/xua_audiohub.xc
index f3793475..1f1831e3 100755
--- a/lib_xua/src/usb_audio/audiohub/xua_audiohub.xc
+++ b/lib_xua/src/usb_audio/audiohub/xua_audiohub.xc
@@ -247,7 +247,7 @@ static inline void TransferAdatTxSamples(chanend c_adat_out, const unsigned samp
 
 #ifndef NO_USB
 #pragma unsafe arrays
-static inline unsigned DoSampleTransfer(chanend c_out, const int readBuffNo, const unsigned underflowWord, client audManage_if i_audMan)
+static inline unsigned DoSampleTransfer(chanend c_out, const int readBuffNo, const unsigned underflowWord, client audManage_if ?i_audMan)
 {
     outuint(c_out, underflowWord);
 
@@ -305,7 +305,7 @@ static inline unsigned DoSampleTransfer(chanend c_out, const int readBuffNo, con
 
 #else /* NO_USB */
 #pragma unsafe arrays
-static inline unsigned DoSampleTransfer(chanend ?c_out, const int readBuffNo, const unsigned underflowWord, client audManage_if i_audMan)
+static inline unsigned DoSampleTransfer(chanend ?c_out, const int readBuffNo, const unsigned underflowWord, client audManage_if ?i_audMan)
 {
     UserBufferManagement(samplesOut, samplesIn[readBuffNo], i_audMan);
     return 0;
@@ -502,7 +502,9 @@ unsigned static deliver(chanend ?c_out, chanend ?c_spd_out,
 #endif
 
     unsigned audioToUsbRatioCounter = 0;
+#if (NUM_PDM_MICS > 0)
     unsigned audioToMicsRatioCounter = 0;
+#endif
 
 #if (AUD_TO_USB_RATIO > 1)
     union i2sInDs3
@@ -1120,7 +1122,7 @@ chanend c_dig_rx,
 #if (NUM_PDM_MICS > 0)
 , chanend c_pdm_in
 #endif
-, client audManage_if i_audMan
+, client audManage_if ?i_audMan
 )
 {
 #if defined (SPDIF_TX) && (SPDIF_TX_TILE == AUDIO_IO_TILE)