diff --git a/reactos/drivers/wdm/audio/backpln/portcls/MiniportWavePci.cpp b/reactos/drivers/wdm/audio/backpln/portcls/MiniportWavePci.cpp
deleted file mode 100644
index 8b137891791..00000000000
--- a/reactos/drivers/wdm/audio/backpln/portcls/MiniportWavePci.cpp
+++ /dev/null
@@ -1 +0,0 @@
-
diff --git a/reactos/drivers/wdm/audio/backpln/portcls/portcls.rbuild b/reactos/drivers/wdm/audio/backpln/portcls/portcls.rbuild
index 303f87f949c..4359c202b5c 100644
--- a/reactos/drivers/wdm/audio/backpln/portcls/portcls.rbuild
+++ b/reactos/drivers/wdm/audio/backpln/portcls/portcls.rbuild
@@ -21,6 +21,7 @@
 	<file>undoc.c</file>
 	<file>resource.c</file>
 	<file>registry.c</file>
+	<file>service_group.c</file>	
 	<file>port.c</file>
 	<file>port_dmus.c</file>
 	<file>port_midi.c</file>
diff --git a/reactos/drivers/wdm/audio/backpln/portcls/service_group.c b/reactos/drivers/wdm/audio/backpln/portcls/service_group.c
new file mode 100644
index 00000000000..f178c3a2af3
--- /dev/null
+++ b/reactos/drivers/wdm/audio/backpln/portcls/service_group.c
@@ -0,0 +1,270 @@
+#include "private.h"
+
+typedef struct
+{
+    LIST_ENTRY Entry;
+    IN PSERVICESINK pServiceSink;
+}GROUP_ENTRY, *PGROUP_ENTRY;
+
+typedef struct
+{
+    IServiceGroupVtbl *lpVtbl;
+
+    LONG ref;
+    LIST_ENTRY ServiceSinkHead;
+
+    BOOL Initialized;
+    BOOL TimerActive;
+    KTIMER Timer;
+    KEVENT DpcEvent;
+    KDPC Dpc;
+
+}IServiceGroupImpl;
+
+const GUID IID_IServiceGroup;
+const GUID IID_IServiceSink;
+
+//---------------------------------------------------------------
+// IUnknown methods
+//
+
+
+NTSTATUS
+STDMETHODCALLTYPE
+IServiceGroup_fnQueryInterface(
+    IServiceGroup* iface,
+    IN  REFIID refiid,
+    OUT PVOID* Output)
+{
+    IServiceGroupImpl * This = (IServiceGroupImpl*)iface;
+    if (IsEqualGUIDAligned(refiid, &IID_IServiceGroup) ||
+        IsEqualGUIDAligned(refiid, &IID_IServiceSink))
+    {
+        *Output = &This->lpVtbl;
+        InterlockedIncrement(&This->ref);
+        return STATUS_SUCCESS;
+    }
+    return STATUS_UNSUCCESSFUL;
+}
+
+ULONG
+STDMETHODCALLTYPE
+IServiceGroup_fnAddRef(
+    IServiceGroup* iface)
+{
+    IServiceGroupImpl * This = (IServiceGroupImpl*)iface;
+
+    return InterlockedIncrement(&This->ref);
+}
+
+ULONG
+STDMETHODCALLTYPE
+IServiceGroup_fnRelease(
+    IServiceGroup* iface)
+{
+    PLIST_ENTRY CurEntry;
+    PGROUP_ENTRY Entry;
+    IServiceGroupImpl * This = (IServiceGroupImpl*)iface;
+
+    InterlockedDecrement(&This->ref);
+
+    if (This->ref == 0)
+    {
+        while(!IsListEmpty(&This->ServiceSinkHead))
+        {
+            CurEntry = RemoveHeadList(&This->ServiceSinkHead);
+            Entry = CONTAINING_RECORD(CurEntry, GROUP_ENTRY, Entry);
+            Entry->pServiceSink->lpVtbl->Release(Entry->pServiceSink);
+            ExFreePoolWithTag(Entry, TAG_PORTCLASS);
+        }
+        KeWaitForSingleObject(&This->DpcEvent, Executive, KernelMode, FALSE, NULL);
+        KeCancelTimer(&This->Timer);
+        ExFreePoolWithTag(This, TAG_PORTCLASS);
+        return 0;
+    }
+    /* Return new reference count */
+    return This->ref;
+}
+
+
+
+//---------------------------------------------------------------
+// IServiceSink methods
+//
+
+VOID
+NTAPI
+IServiceGroup_fnRequestService(
+    IN IServiceGroup * iface)
+{
+    PLIST_ENTRY CurEntry;
+    PGROUP_ENTRY Entry;
+    IServiceGroupImpl * This = (IServiceGroupImpl*)iface;
+
+    CurEntry = This->ServiceSinkHead.Flink;
+    while (CurEntry != &This->ServiceSinkHead)
+    {
+        Entry = CONTAINING_RECORD(CurEntry, GROUP_ENTRY, Entry);
+        Entry->pServiceSink->lpVtbl->RequestService(Entry->pServiceSink);
+        CurEntry = CurEntry->Flink;
+    }
+}
+
+//---------------------------------------------------------------
+// IServiceGroup methods
+//
+
+NTSTATUS
+NTAPI
+IServiceGroup_fnAddMember(
+    IN IServiceGroup * iface,
+    IN PSERVICESINK pServiceSink)
+{
+    PGROUP_ENTRY Entry;
+    IServiceGroupImpl * This = (IServiceGroupImpl*)iface;
+
+    Entry = ExAllocatePoolWithTag(NonPagedPool, sizeof(GROUP_ENTRY), TAG_PORTCLASS);
+    if (!Entry)
+        return STATUS_INSUFFICIENT_RESOURCES;
+
+    Entry->pServiceSink = pServiceSink;
+    pServiceSink->lpVtbl->AddRef(pServiceSink);
+
+    //FIXME
+    //check if Dpc is active
+    InsertTailList(&This->ServiceSinkHead, &Entry->Entry);
+
+    return STATUS_SUCCESS;
+}
+
+VOID
+NTAPI
+IServiceGroup_fnRemoveMember(
+    IN IServiceGroup * iface,
+    IN PSERVICESINK pServiceSink)
+{
+    PLIST_ENTRY CurEntry;
+    PGROUP_ENTRY Entry;
+    IServiceGroupImpl * This = (IServiceGroupImpl*)iface;
+
+    //FIXME
+    //check if Dpc is active
+    //
+
+    CurEntry = This->ServiceSinkHead.Flink;
+    while (CurEntry != &This->ServiceSinkHead)
+    {
+        Entry = CONTAINING_RECORD(CurEntry, GROUP_ENTRY, Entry);
+        if (Entry->pServiceSink == pServiceSink)
+        {
+            RemoveEntryList(&Entry->Entry);
+            pServiceSink->lpVtbl->Release(pServiceSink);
+            ExFreePoolWithTag(Entry, TAG_PORTCLASS);
+            return;
+        }
+        CurEntry = CurEntry->Flink;
+    }
+
+}
+
+VOID
+NTAPI
+IServiceGroupDpc(
+    IN struct _KDPC  *Dpc,
+    IN PVOID  DeferredContext,
+    IN PVOID  SystemArgument1,
+    IN PVOID  SystemArgument2
+    )
+{
+    IServiceGroupImpl * This = (IServiceGroupImpl*)DeferredContext;
+    IServiceGroup_fnRequestService((IServiceGroup*)DeferredContext);
+    KeSetEvent(&This->DpcEvent, 0, FALSE);
+}
+
+
+VOID
+NTAPI
+IServiceGroup_fnSupportDelayedService(
+    IN IServiceGroup * iface)
+{
+    IServiceGroupImpl * This = (IServiceGroupImpl*)iface;
+
+    if (!This->Initialized)
+    {
+        KeInitializeEvent(&This->DpcEvent, NotificationEvent, FALSE);
+        KeInitializeTimerEx(&This->Timer, NotificationTimer);
+        KeInitializeDpc(&This->Dpc, IServiceGroupDpc, (PVOID)This);
+        This->Initialized = TRUE;
+    }
+}
+
+VOID
+NTAPI
+IServiceGroup_fnRequestDelayedService(
+    IN IServiceGroup * iface,
+    IN ULONGLONG ullDelay)
+{
+    LARGE_INTEGER DueTime;
+    IServiceGroupImpl * This = (IServiceGroupImpl*)iface;
+
+    DueTime.QuadPart = ullDelay;
+
+    if (This->Initialized)
+    {
+        KeSetTimer(&This->Timer, DueTime, &This->Dpc);
+        KeClearEvent(&This->DpcEvent);
+    }
+}
+
+VOID
+NTAPI
+IServiceGroup_fnCancelDelayedService(
+    IN IServiceGroup * iface)
+{
+    IServiceGroupImpl * This = (IServiceGroupImpl*)iface;
+
+    if (This->Initialized)
+    {
+        KeCancelTimer(&This->Timer);
+    }
+}
+
+static IServiceGroupVtbl vt_IServiceGroup = 
+{
+    /* IUnknown methods */
+    IServiceGroup_fnQueryInterface,
+    IServiceGroup_fnAddRef,
+    IServiceGroup_fnRelease,
+    IServiceGroup_fnRequestService,
+    IServiceGroup_fnAddMember,
+    IServiceGroup_fnRemoveMember,
+    IServiceGroup_fnSupportDelayedService,
+    IServiceGroup_fnRequestDelayedService,
+    IServiceGroup_fnCancelDelayedService
+};
+
+/*
+ * @unimplemented
+ */
+NTSTATUS NTAPI
+PcNewServiceGroup(
+    OUT PSERVICEGROUP* OutServiceGroup,
+    IN  PUNKNOWN OuterUnknown OPTIONAL)
+{
+    IServiceGroupImpl * This;
+
+    This = ExAllocatePoolWithTag(NonPagedPool, sizeof(IServiceGroupImpl), TAG_PORTCLASS);
+    if (!This)
+        return STATUS_INSUFFICIENT_RESOURCES;
+
+    This->lpVtbl = &vt_IServiceGroup;
+    This->ref = 1;
+    InitializeListHead(&This->ServiceSinkHead);
+    This->Initialized = FALSE;
+    *OutServiceGroup = (PSERVICEGROUP)&This->lpVtbl;
+
+    return STATUS_UNSUCCESSFUL;
+}
+
+
+
diff --git a/reactos/drivers/wdm/audio/backpln/portcls/stubs.c b/reactos/drivers/wdm/audio/backpln/portcls/stubs.c
index b3c377c5056..4d6302fc5c7 100644
--- a/reactos/drivers/wdm/audio/backpln/portcls/stubs.c
+++ b/reactos/drivers/wdm/audio/backpln/portcls/stubs.c
@@ -28,19 +28,6 @@ PcNewDmaChannel(
     return STATUS_UNSUCCESSFUL;
 }
 
-/*
- * @unimplemented
- */
-NTSTATUS NTAPI
-PcNewServiceGroup(
-    OUT PSERVICEGROUP* OutServiceGroup,
-    IN  PUNKNOWN OuterUnknown OPTIONAL)
-{
-    UNIMPLEMENTED;
-    return STATUS_UNSUCCESSFUL;
-}
-
-
 /* ===============================================================
     Power Management
 */