diff --git a/share/scripts/surround_to_stereo.lua b/share/scripts/surround_to_stereo.lua
new file mode 100644
index 0000000000..6ed38e666f
--- /dev/null
+++ b/share/scripts/surround_to_stereo.lua
@@ -0,0 +1,87 @@
+ardour {
+	["type"]    = "dsp",
+	name        = "ACE 5.1 to Stereo",
+	category    = "Amplifier",
+	license     = "MIT",
+	author      = "Ardour Community",
+	description = [[Downmix 5.1 Surround to Stereo]]
+}
+
+function dsp_ioconfig ()
+	return {
+		connect_all_audio_outputs = true, -- override strict-i/o
+		{ audio_in = 6, audio_out = 2},
+	}
+end
+
+function dsp_params ()
+	return {
+		{ ["type"] = "input", name = "Channel Layout", min = 0, max = 1, default = 0, enum = true, scalepoints =
+			{
+				["L R C LFE Ls Rs"] = 0,
+				["L C R Ls Lr LFE"] = 1,
+			}
+		},
+		{ ["type"] = "input", name = "Normalize", min = 0, max = 1, default = 0, toggled = true },
+		{ ["type"] = "input", name = "Include LFE", min = 0, max = 1, default = 0, toggled = true },
+	}
+end
+
+-- see ATSCA/52:2018 Chapter 7.8.2
+clev = 0.707945784 -- -3dB
+slev = 0.707945784 -- -3dB
+norm = 1.0 / (1 + clev + slev)
+normlf = 1.0 / (1 + 2 * clev + slev)
+
+-- the DSP callback function
+function dsp_run (ins, outs, n_samples)
+	local ctrl = CtrlPorts:array() -- get control port array
+	assert (#ins == 6)
+	assert (#outs == 2)
+
+	if ctrl[1] == 0 then
+		-- L R C LFE Ls Rs
+		if ins[1] ~= outs[1] then
+			ARDOUR.DSP.copy_vector (outs[1], ins[1], n_samples) -- left to left
+		end
+		if ins[2] ~= outs[2] then
+			ARDOUR.DSP.copy_vector (outs[2], ins[2], n_samples) -- right to right
+		end
+		ARDOUR.DSP.mix_buffers_with_gain (outs[1], ins[3], n_samples, clev) -- C to left
+		ARDOUR.DSP.mix_buffers_with_gain (outs[2], ins[3], n_samples, clev) -- C to right
+		ARDOUR.DSP.mix_buffers_with_gain (outs[1], ins[5], n_samples, slev) -- Ls
+		ARDOUR.DSP.mix_buffers_with_gain (outs[2], ins[6], n_samples, slev) -- Rs
+		if ctrl[3] > 0 then
+			ARDOUR.DSP.mix_buffers_with_gain (outs[1], ins[4], n_samples, clev) -- LFE to left
+			ARDOUR.DSP.mix_buffers_with_gain (outs[2], ins[4], n_samples, clev) -- LFE to right
+		end
+	else
+		-- L C R Ls Rs LFE
+		if ins[1] ~= outs[1] then
+			ARDOUR.DSP.copy_vector (outs[1], ins[1], n_samples) -- left to left
+		end
+		if ins[2] ~= outs[2] then
+			ARDOUR.DSP.copy_vector (outs[2], ins[2], n_samples) -- copy center
+		end
+		ARDOUR.DSP.apply_gain_to_buffer (outs[2], n_samples, clev); -- C to right
+		ARDOUR.DSP.mix_buffers_no_gain (outs[1], outs[2], n_samples) -- C to left
+		ARDOUR.DSP.mix_buffers_no_gain (outs[2], ins[3], n_samples) -- right to right
+		ARDOUR.DSP.mix_buffers_with_gain (outs[1], ins[4], n_samples, slev) -- Ls
+		ARDOUR.DSP.mix_buffers_with_gain (outs[2], ins[5], n_samples, slev) -- Rs
+		if ctrl[3] > 0 then
+			ARDOUR.DSP.mix_buffers_with_gain (outs[1], ins[6], n_samples, clev) -- LFE to left
+			ARDOUR.DSP.mix_buffers_with_gain (outs[2], ins[6], n_samples, clev) -- LFE to right
+		end
+	end
+
+	if ctrl[2] > 0 then
+		if ctrl[3] > 0 then
+			ARDOUR.DSP.apply_gain_to_buffer (outs[1], n_samples, normlf);
+			ARDOUR.DSP.apply_gain_to_buffer (outs[2], n_samples, normlf);
+		else
+			ARDOUR.DSP.apply_gain_to_buffer (outs[1], n_samples, norm);
+			ARDOUR.DSP.apply_gain_to_buffer (outs[2], n_samples, norm);
+		end
+	end
+
+end