diff --git a/src/emu/disound.cpp b/src/emu/disound.cpp
index 4d7d60265b6..2b0a396a1ac 100644
--- a/src/emu/disound.cpp
+++ b/src/emu/disound.cpp
@@ -394,6 +394,32 @@ device_mixer_interface::~device_mixer_interface()
 }
 
 
+//-------------------------------------------------
+//  input_to_stream_input - convert a device's
+//  input index to a stream and the input index
+//  on that stream
+//-------------------------------------------------
+
+sound_stream *device_mixer_interface::input_to_stream_input(int inputnum, int &stream_inputnum) const
+{
+	assert(inputnum >= 0);
+
+	// scan the list looking for streams owned by this device
+	for (auto &stream : device().machine().sound().streams())
+		if (&stream->device() == &device())
+		{
+			if (inputnum < m_auto_allocated_inputs)
+			{
+				stream_inputnum = inputnum;
+				return stream.get();
+			}
+			inputnum -= m_auto_allocated_inputs;
+		}
+
+	// not found
+	return nullptr;
+}
+
 //-------------------------------------------------
 //  interface_pre_start - perform startup prior
 //  to the device startup
diff --git a/src/emu/disound.h b/src/emu/disound.h
index 37a7df462be..dca30207dd8 100644
--- a/src/emu/disound.h
+++ b/src/emu/disound.h
@@ -81,7 +81,7 @@ public:
 	// helpers
 	int inputs() const;
 	int outputs() const;
-	sound_stream *input_to_stream_input(int inputnum, int &stream_inputnum) const;
+	virtual sound_stream *input_to_stream_input(int inputnum, int &stream_inputnum) const;
 	sound_stream *output_to_stream_output(int outputnum, int &stream_outputnum) const;
 	float input_gain(int inputnum) const;
 	float output_gain(int outputnum) const;
@@ -120,6 +120,9 @@ public:
 	device_mixer_interface(const machine_config &mconfig, device_t &device, int outputs = 1);
 	virtual ~device_mixer_interface();
 
+	// helpers
+	virtual sound_stream *input_to_stream_input(int inputnum, int &stream_inputnum) const override;
+
 protected:
 	// optional operation overrides
 	virtual void interface_pre_start() override;