diff --git a/src/mame/audio/n8080.cpp b/src/mame/audio/n8080.cpp
index d566198c3e6..f3a27c3869c 100644
--- a/src/mame/audio/n8080.cpp
+++ b/src/mame/audio/n8080.cpp
@@ -129,10 +129,9 @@ void n8080_state::spacefev_sound_pins_changed()
 	{
 		start_mono_flop(2, attotime::from_usec(550 * 22 * 33));
 	}
-	if (changes & ((1 << 0x2) | (1 << 0x3) | (1 << 0x5)))
-	{
-		generic_pulse_irq_line(*m_audiocpu, 0, 2);
-	}
+
+	bool irq_active = (~m_curr_sound_pins & ((1 << 0x2) | (1 << 0x3) | (1 << 0x5))) != 0;
+	m_audiocpu->set_input_line(INPUT_LINE_IRQ0, irq_active ? ASSERT_LINE : CLEAR_LINE);
 }
 
 
@@ -152,25 +151,22 @@ void n8080_state::sheriff_sound_pins_changed()
 	{
 		start_mono_flop(1, attotime::from_usec(550 * 33 * 33));
 	}
-	if (changes & ((1 << 0x2) | (1 << 0x3) | (1 << 0x5)))
-	{
-		generic_pulse_irq_line(*m_audiocpu, 0, 2);
-	}
+
+	bool irq_active = (~m_curr_sound_pins & ((1 << 0x2) | (1 << 0x3) | (1 << 0x5))) != 0;
+	m_audiocpu->set_input_line(INPUT_LINE_IRQ0, irq_active ? ASSERT_LINE : CLEAR_LINE);
 }
 
 
 void n8080_state::helifire_sound_pins_changed()
 {
-	uint16_t changes = ~m_curr_sound_pins & m_prev_sound_pins;
+	//uint16_t changes = ~m_curr_sound_pins & m_prev_sound_pins;
 
 	/* ((m_curr_sound_pins >> 0xa) & 1) not emulated */
 	/* ((m_curr_sound_pins >> 0xb) & 1) not emulated */
 	/* ((m_curr_sound_pins >> 0xc) & 1) not emulated */
 
-	if (changes & (1 << 6))
-	{
-		generic_pulse_irq_line(*m_audiocpu, 0, 2);
-	}
+	bool irq_active = (~m_curr_sound_pins & (1 << 6)) != 0;
+	m_audiocpu->set_input_line(INPUT_LINE_IRQ0, irq_active ? ASSERT_LINE : CLEAR_LINE);
 }