diff --git a/src/mame/drivers/toaplan2.cpp b/src/mame/drivers/toaplan2.cpp
index db182220e7e..20c6f6057c8 100644
--- a/src/mame/drivers/toaplan2.cpp
+++ b/src/mame/drivers/toaplan2.cpp
@@ -3373,7 +3373,7 @@ void toaplan2_state::ghox(machine_config &config)
 	/* sound hardware */
 	SPEAKER(config, "mono").front_center();
 
-	YM2151(config, "ymsnd", 27_MHz_XTAL/8).add_route(ALL_OUTPUTS, "mono", 1.0); // verified on pcb
+	YM2151(config, "ymsnd", 27_MHz_XTAL/8).add_route(ALL_OUTPUTS, "mono", 0.5); // verified on pcb
 }
 
 /* probably dogyuun, vfive and kbash use the same decryption table;