diff --git a/src/emu/disound.cpp b/src/emu/disound.cpp
index 2b0a396a1ac..4d7d60265b6 100644
--- a/src/emu/disound.cpp
+++ b/src/emu/disound.cpp
@@ -394,32 +394,6 @@ 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 dca30207dd8..37a7df462be 100644
--- a/src/emu/disound.h
+++ b/src/emu/disound.h
@@ -81,7 +81,7 @@ public:
 	// helpers
 	int inputs() const;
 	int outputs() const;
-	virtual sound_stream *input_to_stream_input(int inputnum, int &stream_inputnum) const;
+	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;
@@ -120,9 +120,6 @@ 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;