diff --git a/scripts/synth1.lua b/scripts/synth1.lua
index 046d27404b..264d6dcb99 100644
--- a/scripts/synth1.lua
+++ b/scripts/synth1.lua
@@ -11,8 +11,11 @@ ardour {
 function dsp_ioconfig ()
 	return
 	{
-		{ audio_in = 0, audio_out = -1}, -- any number of channels
-	--	{ audio_in = 0, audio_out =  4}, -- values >  0, precisely N channels
+	--	{ audio_in = 0, audio_out = -1}, -- any number of channels
+	--	{ audio_in = 0, audio_out =  1}, -- values >  0, precisely N channels
+		{ audio_in = 0, audio_out =  2}, -- values >  0, precisely N channels
+		{ audio_in = 0, audio_out =  4}, -- values >  0, precisely N channels
+		{ audio_in = 0, audio_out =  8}, -- values >  0, precisely N channels
 	--	{ audio_in = 0, audio_out = -6}, -- values < -2, up to -N channels, here 1,..,6
 	}
 end