diff --git a/src/mame/drivers/zaxxon.c b/src/mame/drivers/zaxxon.c
index 09cd1c3fc3c..9429196fb95 100644
--- a/src/mame/drivers/zaxxon.c
+++ b/src/mame/drivers/zaxxon.c
@@ -997,10 +997,10 @@ static MACHINE_CONFIG_DERIVED( congo, root )
 	/* sound hardware */
 	MCFG_SPEAKER_STANDARD_MONO("mono")
 
-	MCFG_SOUND_ADD("sn1", SN76496, SOUND_CLOCK)
+	MCFG_SOUND_ADD("sn1", SN76489A, SOUND_CLOCK) // schematic shows sn76489A
 	MCFG_SOUND_ROUTE(ALL_OUTPUTS, "mono", 1.0)
 
-	MCFG_SOUND_ADD("sn2", SN76496, SOUND_CLOCK/4)
+	MCFG_SOUND_ADD("sn2", SN76489A, SOUND_CLOCK/4) // schematic shows sn76489A
 	MCFG_SOUND_ROUTE(ALL_OUTPUTS, "mono", 1.0)
 
 	MCFG_FRAGMENT_ADD(congo_samples)