diff --git a/src/processor/memory/mmio/apu.rs b/src/processor/memory/mmio/apu.rs
index 785d8e7..3f34c40 100644
--- a/src/processor/memory/mmio/apu.rs
+++ b/src/processor/memory/mmio/apu.rs
@@ -1,5 +1,7 @@
-use std::sync::mpsc::{channel, Sender};
-
+use self::{
+    channels::EnvelopeMode,
+    types::{Channels, DacSample, Mixer, VinEnable, Volume},
+};
 use crate::{
     processor::{
         memory::{masked_update, Address},
@@ -13,10 +15,10 @@ use cpal::{
     Device, Stream, StreamConfig,
 };
 use samplerate::{ConverterType, Samplerate};
-
-use self::channels::{EnvelopeMode, NoiseChannel, PwmChannel, WaveChannel};
+use std::sync::mpsc::{channel, Sender};
 
 mod channels;
+mod types;
 
 const MEM_START: usize = 0xFF10;
 const MEM_SIZE: usize = 0xFF40 - MEM_START;
@@ -25,107 +27,6 @@ const fn reg(a: Address) -> usize {
     (a as usize) - MEM_START
 }
 
-struct Channels {
-    one: PwmChannel,
-    two: PwmChannel,
-    three: WaveChannel,
-    four: NoiseChannel,
-}
-
-impl Default for Channels {
-    fn default() -> Self {
-        Self {
-            one: PwmChannel::new(true),
-            two: PwmChannel::new(false),
-            three: WaveChannel::new(false),
-            four: NoiseChannel::new(false),
-        }
-    }
-}
-
-#[derive(Default)]
-struct VinEnable {
-    left: bool,
-    right: bool,
-}
-
-enum Volume {
-    Muted,
-    Enabled,
-}
-
-impl Volume {
-    fn scale(&self) -> f32 {
-        match self {
-            Volume::Muted => 0.,
-            Volume::Enabled => 1.,
-        }
-    }
-
-    fn bool(&self) -> bool {
-        match self {
-            Volume::Muted => false,
-            Volume::Enabled => true,
-        }
-    }
-
-    fn from_bool(val: bool) -> Self {
-        if val {
-            Self::Enabled
-        } else {
-            Self::Muted
-        }
-    }
-}
-
-struct ChannelVol {
-    left: Volume,
-    right: Volume,
-}
-
-impl Default for ChannelVol {
-    fn default() -> Self {
-        Self {
-            left: Volume::Muted,
-            right: Volume::Muted,
-        }
-    }
-}
-
-struct Mixer {
-    vol_left: u8,
-    vol_right: u8,
-    ch1: ChannelVol,
-    ch2: ChannelVol,
-    ch3: ChannelVol,
-    ch4: ChannelVol,
-}
-
-impl Default for Mixer {
-    fn default() -> Self {
-        Self {
-            vol_left: 7,
-            vol_right: 7,
-            ch1: Default::default(),
-            ch2: Default::default(),
-            ch3: Default::default(),
-            ch4: Default::default(),
-        }
-    }
-}
-
-#[derive(Clone, Copy)]
-struct DacSample {
-    one: f32,
-    two: f32,
-}
-
-impl Default for DacSample {
-    fn default() -> Self {
-        Self { one: 0., two: 0. }
-    }
-}
-
 impl DacSample {
     fn mixed(&self, mixer: &Mixer) -> [f32; 2] {
         let left = (self.one * mixer.ch1.left.scale()) + (self.two * mixer.ch2.left.scale());
diff --git a/src/processor/memory/mmio/apu/types.rs b/src/processor/memory/mmio/apu/types.rs
new file mode 100644
index 0000000..3da9f7a
--- /dev/null
+++ b/src/processor/memory/mmio/apu/types.rs
@@ -0,0 +1,102 @@
+use super::channels::{NoiseChannel, PwmChannel, WaveChannel};
+
+pub(super) struct Channels {
+    pub(super) one: PwmChannel,
+    pub(super) two: PwmChannel,
+    pub(super) three: WaveChannel,
+    pub(super) four: NoiseChannel,
+}
+
+impl Default for Channels {
+    fn default() -> Self {
+        Self {
+            one: PwmChannel::new(true),
+            two: PwmChannel::new(false),
+            three: WaveChannel::new(false),
+            four: NoiseChannel::new(false),
+        }
+    }
+}
+
+#[derive(Default)]
+pub(super) struct VinEnable {
+    pub(super) left: bool,
+    pub(super) right: bool,
+}
+
+pub(super) enum Volume {
+    Muted,
+    Enabled,
+}
+
+impl Volume {
+    pub(super) fn scale(&self) -> f32 {
+        match self {
+            Volume::Muted => 0.,
+            Volume::Enabled => 1.,
+        }
+    }
+
+    pub(super) fn bool(&self) -> bool {
+        match self {
+            Volume::Muted => false,
+            Volume::Enabled => true,
+        }
+    }
+
+    pub(super) fn from_bool(val: bool) -> Self {
+        if val {
+            Self::Enabled
+        } else {
+            Self::Muted
+        }
+    }
+}
+
+pub(super) struct ChannelVol {
+    pub(super) left: Volume,
+    pub(super) right: Volume,
+}
+
+impl Default for ChannelVol {
+    fn default() -> Self {
+        Self {
+            left: Volume::Muted,
+            right: Volume::Muted,
+        }
+    }
+}
+
+pub(super) struct Mixer {
+    pub(super) vol_left: u8,
+    pub(super) vol_right: u8,
+    pub(super) ch1: ChannelVol,
+    pub(super) ch2: ChannelVol,
+    pub(super) ch3: ChannelVol,
+    pub(super) ch4: ChannelVol,
+}
+
+impl Default for Mixer {
+    fn default() -> Self {
+        Self {
+            vol_left: 7,
+            vol_right: 7,
+            ch1: Default::default(),
+            ch2: Default::default(),
+            ch3: Default::default(),
+            ch4: Default::default(),
+        }
+    }
+}
+
+#[derive(Clone, Copy)]
+pub(super) struct DacSample {
+    pub(super) one: f32,
+    pub(super) two: f32,
+}
+
+impl Default for DacSample {
+    fn default() -> Self {
+        Self { one: 0., two: 0. }
+    }
+}
diff --git a/src/processor/timer.rs b/src/processor/timer.rs
index dfaa1b0..965e074 100644
--- a/src/processor/timer.rs
+++ b/src/processor/timer.rs
@@ -1,9 +1,8 @@
-use std::time::Duration;
-
 use crate::{
     processor::Cpu,
     util::{get_bit, set_bit},
 };
+use std::time::Duration;
 
 pub(super) struct Timers {
     div_counter: usize,