diff --git a/sources/APU/APU.hpp b/sources/APU/APU.hpp
index 780ef58..aaf273e 100644
--- a/sources/APU/APU.hpp
+++ b/sources/APU/APU.hpp
@@ -144,7 +144,7 @@ namespace ComSquare::APU
 		std::shared_ptr<MemoryMap> _map;
 
 		//! @brief Total size of the buffer containing samples
-        static constexpr int32_t bufferSize = 0x20000;
+        static constexpr int32_t bufferSize = 0x10000;
         //! @brief Buffer containing samples to be played
 		int16_t _soundBuffer[bufferSize];
 
diff --git a/sources/APU/DSP/DSP.cpp b/sources/APU/DSP/DSP.cpp
index 2321ae7..a3036a0 100644
--- a/sources/APU/DSP/DSP.cpp
+++ b/sources/APU/DSP/DSP.cpp
@@ -8,11 +8,10 @@
 
 namespace ComSquare::APU::DSP
 {
-	DSP::DSP(int16_t *buffer, int32_t size, std::weak_ptr<MemoryMap> map) : _map(map)
+	DSP::DSP(int16_t *buffer, uint32_t size, std::weak_ptr<MemoryMap> map) : _map(map)
 	{
 		this->_state.buffer = buffer;
-		this->_state.bufferStart = buffer;
-		this->_state.bufferEnd = buffer + size;
+		this->_state.bufferSize = size;
 	}
 
 	uint8_t DSP::read(uint24_t addr) const
@@ -796,6 +795,6 @@ namespace ComSquare::APU::DSP
 
 	int32_t DSP::getSamplesCount() const
 	{
-		return this->_state.buffer - this->_state.bufferStart;
+		return this->_state.bufferOffset;
 	}
 }
\ No newline at end of file
diff --git a/sources/APU/DSP/DSP.hpp b/sources/APU/DSP/DSP.hpp
index 4ea52f4..3ae3fd0 100644
--- a/sources/APU/DSP/DSP.hpp
+++ b/sources/APU/DSP/DSP.hpp
@@ -46,12 +46,20 @@ namespace ComSquare::APU::DSP
 		std::array<uint8_t, 8> FIR;
 		//! @brief Echo data start register (ESA)
 		uint8_t data;
+		//! @brief Offset position after data start
+		uint16_t offset;
 		//! @brief Echo delay size register (EDL)
 		uint8_t delay;
 		//! @brief Echo enabled (5th bit FLG)
 		bool enabled = true;
 		//! @brief Last sound produced for each voice in each channel
 		std::array<std::array<int16_t, 8>, 2> history;
+		//! @brief Current position inside history
+		uint8_t historyOffset;
+		//! @brief Address of the current echo
+		uint16_t address;
+		//! @brief Current of value of the echo
+		uint8_t value;
 		//! @brief Current sound to echo
 		std::array<uint16_t, 2> input;
 		//! @brief Current sound echoed produced
@@ -123,6 +131,8 @@ namespace ComSquare::APU::DSP
 		uint8_t gain;
 		//! @brief envelope associated with this voice
 		uint8_t envx;
+		//! @brief Wave height associated with this voice
+		uint8_t outx;
 		//! @brief Sample end register (ENDX)
 		bool endx : 1;
 
@@ -176,10 +186,10 @@ namespace ComSquare::APU::DSP
 		uint8_t voice = 0;
 		//! @brief Current buffer of samples
 		int16_t *buffer;
-		//! @brief Limit of the buffer
-		int16_t *bufferEnd;
-		//! @brief Beginning of the buffer
-		int16_t *bufferStart;
+		//! @brief Size of buffer
+		uint32_t bufferSize;
+		//! @brief Current position in the buffer of samples
+		uint32_t bufferOffset;
 	};
 
 	struct Timer {
@@ -404,6 +414,10 @@ namespace ComSquare::APU::DSP
 		int32_t interpolate(const Voice &voice);
 		void runEnvelope(Voice &voice);
 
+		int32_t loadFIR(bool channel, int fir);
+		void loadEcho(bool channel);
+		int16_t outputEcho(bool channel);
+
 		void timerTick();
 		bool timerPoll(uint32_t rate);
 
@@ -414,7 +428,7 @@ namespace ComSquare::APU::DSP
 		uint8_t _readRAM(uint24_t addr);
 		void _writeRAM(uint24_t addr, uint8_t data);
 	public:
-		DSP(int16_t *buffer, int32_t size, std::weak_ptr<MemoryMap> map);
+		DSP(int16_t *buffer, uint32_t size, std::weak_ptr<MemoryMap> map);
 		DSP(const DSP &) = default;
 		DSP &operator=(const DSP &) = default;
 		~DSP() = default;
diff --git a/sources/APU/DSP/Echo.cpp b/sources/APU/DSP/Echo.cpp
index 5b4d999..51823c4 100644
--- a/sources/APU/DSP/Echo.cpp
+++ b/sources/APU/DSP/Echo.cpp
@@ -6,34 +6,89 @@
 
 namespace ComSquare::APU::DSP
 {
+	int32_t DSP::loadFIR(bool channel, int fir)
+	{
+		int32_t sample = this->_echo.history[channel][this->_echo.historyOffset + fir + 1];
+
+		return (sample * this->_echo.FIR[fir]) >> 6;
+	}
+
+	void DSP::loadEcho(bool channel)
+	{
+		uint16_t address = this->_echo.address + channel * 2;
+		uint8_t low = this->_readRAM(address++);
+		uint8_t high = this->_readRAM(address);
+		int16_t echo = (high << 8) + low;
+
+		this->_echo.history[channel][this->_echo.historyOffset] = echo >> 1;
+	}
+
+	int16_t DSP::outputEcho(bool channel)
+	{
+		int16_t master = this->_master.output[channel] * this->_master.volume[channel] >> 7;
+		int16_t echo = this->_echo.input[channel] * this->_echo.input[channel] >> 7;
+
+		return master + echo;
+	}
+
 	void DSP::echo22()
 	{
+		this->_echo.historyOffset += 1;
+		this->_echo.address = (this->_echo.value << 8) + this->_echo.offset;
 
+		this->loadEcho(0);
+
+		this->_echo.input[0] = this->loadFIR(0, 0);
+		this->_echo.input[1] = this->loadFIR(1, 0);
 	}
 
 	void DSP::echo23()
 	{
+		this->loadEcho(1);
 
+		this->_echo.input[0] += this->loadFIR(0, 1) + this->loadFIR(0, 2);
+		this->_echo.input[1] += this->loadFIR(1, 1) + this->loadFIR(1, 2);
 	}
 
 	void DSP::echo24()
 	{
-
+		this->_echo.input[0] += this->loadFIR(0, 3) + this->loadFIR(0, 4) + this->loadFIR(0, 5);
+		this->_echo.input[1] += this->loadFIR(1, 3) + this->loadFIR(1, 4) + this->loadFIR(1, 5);
 	}
 
 	void DSP::echo25()
 	{
-
+		this->_echo.input[0] += this->loadFIR(0, 6) + this->loadFIR(0, 7);
+		this->_echo.input[1] += this->loadFIR(1, 6) + this->loadFIR(1, 7);
 	}
 
 	void DSP::echo26()
 	{
+		this->_master.output[0] = this->outputEcho(0);
 
+		this->_echo.output[0] += this->_echo.input[0] * this->_echo.feedback >> 7;
+		this->_echo.output[1] += this->_echo.input[1] * this->_echo.feedback >> 7;
 	}
 
 	void DSP::echo27()
 	{
+		int16_t outputLeft = this->_master.output[0];
+		int16_t outputRight = this->outputEcho(1);
 
+		this->_master.output[0] = 0;
+		this->_master.output[1] = 0;
+
+		if (this->_master.mute) {
+			outputLeft = 0;
+			outputRight = 0;
+		}
+
+		srand(time(NULL));
+		this->_state.buffer[this->_state.bufferOffset] = outputLeft + (INT16_MIN + rand() % (INT16_MAX + 1 - INT16_MIN));
+		this->_state.buffer[this->_state.bufferOffset + 1] = outputRight + (INT16_MIN + rand() % (INT16_MAX + 1 - INT16_MIN));
+		this->_state.bufferOffset += 2;
+		if (this->_state.bufferOffset >= this->_state.bufferSize)
+			this->_state.bufferOffset = 0;
 	}
 
 	void DSP::echo28()
diff --git a/sources/APU/DSP/Voice.cpp b/sources/APU/DSP/Voice.cpp
index eccc7a2..197885b 100644
--- a/sources/APU/DSP/Voice.cpp
+++ b/sources/APU/DSP/Voice.cpp
@@ -141,16 +141,16 @@ namespace ComSquare::APU::DSP
 
 	void DSP::voice7(Voice &voice)
 	{
-
+		this->_latch.envx = voice.envx;
 	}
 
 	void DSP::voice8(Voice &voice)
 	{
-
+		voice.outx = this->_latch.outx;
 	}
 
 	void DSP::voice9(Voice &voice)
 	{
-
+		voice.envx = this->_latch.envx;
 	}
 }
\ No newline at end of file